Thanks to batteries RVs are useable and even comfortable for days without the need for hookups. As long as you have charged RV batteries and water in the fresh tank you can flush the toilet, take a shower, use your lights, plus RV Batteries can also power 110V/120V electronics like your TV if your RV is equipped with a power inverter.
Unfortunately even the best batteries don’t last forever and most RV manufacturers do not include the best batteries with new RVs. Even worse is that most RV manufacturers install cheap, single-stage battery converter chargers. As a result, most RV owners have a dead set of batteries within the first year or two of purchase – and sometimes even sooner.
In this article I’ll explain what types of batteries are available, and how RV batteries work. I’ll also show you our battery setup and explain why I chose Trojan T-105 6V Golf Cart Batteries.
I’ll cover the basics, which is still quite a lot of information. Hopefully this article helps you find the right battery and converter setup for your RV.
Article Index
- Single Stage RV Battery Charger/Converter
- The Solution: The 4-Stage Smart Battery Charger / Converter
- Which Smart Charger Converter Should You Get?
- Battery Amp Hours explained
- The Most Common types of RV House Batteries
- What Batteries are Right For Your RV?
- Our Battery Setup
- How Lead Acid Batteries Work
- How to Damage or Ruin RV House Batteries:
- How to Maintain RV Batteries:
- How To Clean Battery Terminals
- How to Add Water to RV House Batteries
- Wrapping Up
Single Stage RV Battery Charger/Converter
I’m going to first address the cause of most RV battery problems – the single-stage battery charger/converter. If your RV has house batteries then it also has a charger/converter. Nicer and some newer RVs may already have a ‘smart’ charger, or 4-stage charger. If that’s your RV then skip this section.
Most RVs include a converter / charger – a device that turns 120-volt A/C power into 12-volt DC power. Typically this unit also charges the RV house batteries. The converter powers your 12-volt appliances when you’re plugged into shore power. This includes lights, vent fans, your TV antenna, water pump, electric awnings, etc.. You might be thinking, “Wait a minute, I thought my batteries did that?” But when plugged into shore power you can remove your RV house batteries and your 12-volt appliances will still work.
The converter also sends some of that 12-volt power to the batteries to charge them – which is why Converters are also called Battery Chargers – or Converter/Chargers.
The problem is that many factory-installed converters use just one consistent voltage – usually 13.6V to 13.8V to charge and maintain RV house batteries. This is why they’re called ‘single stage’ converter/chargers. This is a problem because batteries charge faster, last longer, and function better when charged by a 4 stage ‘smart charger’. The four stages – which I’ll cover below – are bulk (14.4V – 14.8V), absorption (13.8V – 14.2V), float (13.2), and then periodic equalization charge (15.5V) to ensure no battery sulfation (a poor or reduced battery charge) takes place.
When you maintain batteries at 13.7V they take forever to charge on the front end if they fully charge at all, and then they get cooked once the battery is charged. And when I say cooked, I’m not kidding. the charger literally boils some water out of the batteries, which speeds up the sulfation process and the batteries require more frequent maintenance – or they die much faster than they otherwise would.
By starting with a heavy bulk charge, and then switching to an absorption charge when the battery is ~80% full and a float/trickle charge at 95% full, your house batteries will reach 100% capacity without risk of sulfation or outgassing. They’ll also charge much faster – especially the first 80% – and last much longer.
Finally, keeping the batteries at a 13.2V float charge keeps them cooler and they require less maintenance (water & terminal cleaning) as a result. This also prevents excessive sulfation, which is the death of any lead acid battery.
Battery Charger/Converters & RV Generators Issue
Another issue that a lot of RVers run into is trying to charge their batteries by running the generator. If you have a smart charger (below), then you can get a pretty good charge (85%) in a couple hours.
If your RV is equipped with a single-stage converters (like ours was), then trying to charge your batteries by running the generator is expensive and mostly pointless. Charging the batteries from 50% discharge at a consistent 13.7 Volts takes much longer without the higher voltage bulk (14.8V) and absorption (14.2V) stages that a smart converter provides.
If you plan to boondock and charge your batteries with your RV generator then upgrading to a smart converter charger is a must.
The Solution: The 4-Stage Smart Battery Converter/Charger
After upgrading our batteries I replaced our converter with an IOTA-DLS45 4-Stage Converter/Charger.
As newby RVers we were told we’d need to buy a new set of house batteries every year on average. I’ve also read on forums that house batteries only last 1 – 2 years, and that’s ‘just the way it is.’
In reality the single-stage battery charger/converter installed in most RVs is the problem.
With a proper 4-stage smart converter/battery charger like our IOTA, our Trojan T105 batteries should last 7 – 10 years. I’ve heard of Trojan batteries lasting even longer in some case, as battery life varies some based on use, care, and number of charge cycles.
A new set of batteries costs $250+ so by replacing them every decade vs. every year or two, we save hundreds of dollars. As an added bonus our batteries work as designed, and we don’t have to worry about running out of power.
Imagine watching a movie before bed without worrying if the heater blower will have enough power to run all night. Or if the toilet will flush in the morning as the water pump runs on house batteries. That’s standard for us now that I’ve installed our Iota Smart Charger Converter and Trojan T-105 Batteries. Meanwhile, I read about people struggling with undercharged or half-dead batteries every day.
You may need to replace your batteries if they’ve been chronically undercharged or abused by a single-stage converter. I recommend upgrading the charger converter first, and then replace the batteries if they still aren’t holding a charge.
Which Smart Charger Converter Should You Get?
Both Iota and Progressive Dynamics make excellent smart battery charger converters and it’s a matter of preference between the two. The IOTA units are less money and have a smaller footprint, so that’s why I chose the IOTA DLS45.
The easiest way to get the ‘right’ smart charger is to match the amperage of your current battery charger converter. Some people get confused and try to match the line amperage (30amp or 50amp) of their RV. These are measuring two different things. Your RV plug is 110V, the charger converter is 12V. That’s why our 30-amp RV has a 45-amp charger converter.
I’ve linked to a few of the more popular smart chargers below. The first link is the IOTA we use. RVs larger than ours likely use the 55 amp model instead.
IOTA-DLS 45amp 4-Stage Smart Converter/Charger on Amazon.com →
IOTA-DLS 55amp 4-Stage Smart Converter Charger on Amazon.com →
Battery Amp Hours explained
Before I get into battery types, I think it’s helpful to go over battery amp hours. Amp Hours are the most useful and most common way to measure RV battery storage capacity. It’s easiest to think of Amp Hours (AH) as units of electricity in a battery ‘gas tank’.
1 amp hour is the amount of power it takes to run a 1 amp electrical draw for 1 hour. For example: An LED lightbulb may use 0.5 AH. Using 1 LED lightbulb for 6 hours will use 3 Amp Hours (1 x 0.5 x 6 = 3). 6 LED lightbulbs for 1 hour will also use 3 Amp Hours (6 x 1 x .5 = 3). Assuming we have 100AH of available charge in our RV batteries we could run those 6 lights for just over 33 hours before emptying the batteries ‘tank’ (6 x 33.3 x .5 = 100). Make sense?
Amp Hours are usually measured using the ’20-hour rate’. This is calculated by evenly discharging a battery from fully charged to empty over 20 hours. The total amount of power provided during that time is the 20 hour rate.
Why the 20-hour distinction? Because batteries supply more AH when power is used slowly and less AH when power is used quickly. The 20 hours rate is a good measure for one day’s worth of use.
The most important thing about the 20-hour rate is that it gives us good comparative data between batteries. Our Trojan T-105s have 225AH of capacity at 20 hours. Trojan also makes higher capacity batteries. In my experience 225AH is plenty for two people.
The Most Common types of RV House Batteries
Once you have a decent smart converter/charger, either your current batteries will begin to hold a charge – or they won’t. If they don’t then no big surprise as you’re probably reading this article because your batteries died in the first place. It was still very much worth it to upgrade to a smart converter so that your next set of batteries won’t suffer the same fate as the last set.
Below I’ll go over the most common types of batteries used by RVers.
12-Volt RV/Marine Flooded Cell Lead Acid Batteries
Most RVs come new with 1 or 2 12V Rv/Marine Flooded Cell Batteries. While manufacturers label these ‘deep cycle’ batteries, they’re really a hybrid starter/deep cycle battery.
The difference may sound like marketing, but in real world use true ‘deep cycle’ batteries can be more deeply discharged and then recharged than a hybrid starter/deep cycle battery. Deep cycle batteries also last longer, and usually have higher capacity too.
For people plugged into full hookups most of the time, an inexpensive set of 12-Volt RV/Marine batteries are a good choice. They usually cost less than $100 each and can be bought at Walmart and most auto-parts stores. These batteries will still benefit by the use of a 4-stage smart charger, as they’ll last significantly longer and provide more power.
6-Volt Deep Cycle Batteries aka Golf Cart Batteries
Deep cycle batteries can be discharged 80% and then fully recharged without damage. Don’t try that with RV/Marine hybrid batteries!
6-Volt Deep Cycle Batteries are designed for golf cart use. These batteries are workhorses that can take a lot of abuse and last a long time.
If you full-time or most-time and spend a fair bit of your time traveling, boondocking, and off-hookups, then these are the batteries I recommend.
Our Trojan T105 Batteries are 6V Golf Cart batteries, which I bought, and then wired in series, essentially creating 1 big 12-volt battery. Note that to use 6V batteries you must have an even number of batteries. You can’t wire 3 or 5 of these together and get the necessary 12-Volts.
12-Volt or 6-Volt AGM Batteries
In regular lead-acid battery cells, the acid is in liquid form. AGM and other VRLA (valve regulate lead acid) batteries keep the acid electrolyte solution immobilized either by soaking a fiberglass mat in it (Absorbed Glass-Mat batteries), or by turning the liquid into a paste-like gel by the addition of silica and other gelling agents (gel batteries).
The net result of this is mostly good and a little bit bad.
The good is that AGM batteries hold a charge much better than traditional flooded cell batteries. I recommend AGM batteries if you store your RV for months at a time. AGM batteries discharge very slowly during storage.
That means you can leave the batteries in your RV between trips without having to worry about keeping them charged. I’d still remove them and trickle charge them in the winter, but even then they’ll only need to be charged every few months – vs. every couple weeks for flooded lead acid.
The bad is that AGM batteries cost roughly double what traditional flooded cell batteries. A comparable AGM also weighs more than a flooded cell battery – in both cases assuming similar Amp-Hour capacity.
Lastly, it’s not possible to open, inspect, or fill AGM batteries. This means they won’t last as long as well-cared for flooded cell batteries – which is because AGM batteries still outgas. This is also why they’re called ‘Valve Regulated Lead Acid’ batteries. They have a valve that allows outgassing when pressure builds up in the battery due to overcharging or rapid discharge (electrolysis). As the batteries are sealed any gases that are vented can’t be replaced.
Lithium (LiFePO4) Batteries
We don’t have Lithium batteries so I can’t speak to their real world use. Lithium Iron Phosphate batteries offer many features that make them a good choice over lead acid batteries, such as faster charging, more capacity per size/weight, more consistent power discharge, deeper depth of discharge, and more recharge cycles (longevity).
Unfortunately Lithium batteries are also almost 10-times more expensive than comparable lead acid batteries – or 5-times more expensive than AGM batteries, so unless you boondock a lot and rely on Solar Power Lithium batteries, they are not a practical or affordable option for most RVers.
If you’d like to know more about lithium batteries for RVers, I recommend reading the Technomads Lithium Battery Page.
What Batteries are Right For Your RV?
AGM Batteries are the best option for most RVers. I say this largely because most RVers part time, and most people don’t need another maintenance item (gotta fill/charge the RV batteries) in their brain space.
For full-timers, boondockers, and those who like to keep an eye on and maintain things – and those who want the best bang for their buck – 6-Volt flooded cell (Golf Cart) batteries are the way to go.
If you never leave the RV park, stick with inexpensive 12V RV/Marine batteries. If you never leave the RV park, then you really only need one as a backup if the power goes out.
Our Battery Setup
I’d known that our batteries weren’t holding much charge for a while, but it took a storm in Blaine, WA that knocked down power lines for us to make a battery upgrade a priority. The first night after the storm while running on 100% battery power our lights were dim by 9pm and our vent fans were useless – not good!
We also had an RV trip to Mt Lassen Volcanic National Park planned, and knew we’d be off hookups for several days. New batteries were a must.
On the plus side, I’d been planning to upgrade our batteries for some time, as we’d made a goal to do more boondocking (camping outside of developed campgrounds, so no hookups). We’d also like to spend more time in State & National Parks and other off-grid camping.
‘Our RV came from the factory with two NAPA 12-Volt RV/Marine ‘Deep Cycle’ batteries. RV/Marine batteries are installed in most RVs as they are inexpensive. They’ll get the job done on the dealer lot, but I wouldn’t expect them to last.
Our RV house batteries are installed under the entrance step in a ventilated compartment. There’s only room for two batteries, but considering the size of our RV and our power requirements, two batteries is plenty for us.
I measured the space, determined I could fit two Trojan T-105 Batteries, then I went to Battery Systems of Bend, OR, and picked up two fresh Trojans.
It’s important to wire 6V batteries correctly. I’ve included this diagram (that I made) to illustrated the right way to wire 6V batteries vs. 12V batteries.
To ensure that our new Trojan batteries will last, I ordered the DLS-45 IOTA Smart Charger and installed it in place or our single-stage converter charger. I didn’t document this unfortunately – although every setup is different, so not sure that would have helped much.
How Lead Acid Batteries Work
The vast majority of RVs use some type of lead-acid battery. This includes both flooded cell (most common) and AGM (Absorbed Glass Mat – also common) batteries. Even your engine starter batteries are a type of sealed lead-acid battery.
In conventional lead-acid cell batteries the diluted acid is in liquid form. This is why they’re called “flooded” or “wet” cell batteries. AGM batteries have the same lead-acid chemistry, but the acid electrolyte solution is immobilized, either by soaking a fiberglass mat in it (absorbed-glass-mat batteries), or by turning the liquid into a paste-like gel by the addition of silica and other gelling agents (gel-cell batteries).
Lead acid batteries contain 2 lead plates (electrodes) suspended in sulphuric acid (electrolyte). To be fully accurate the negative plate is lead and the positive plate is lead dioxide. As power is pulled from the battery (discharge), the lead and acid in the battery undergo a chemical reaction that produces lead sulphate and water.
As the battery is recharged the lead sulphate and water are turned back into lead, lead dioxide, and acid.
Every time you drain your battery and then recharge it it goes through one ‘charge cycle’. Batteries have a limit to the number of charge cycles they can go through before they start to degrade. This is why older batteries don’t hold charge as well as new batteries.
For the full chemical reactions, read this wikipedia article
Don’t Damage Your RV House Batteries!
RV House Batteries are designed to be discharged and recharged many hundreds of times. However there are 3 things you can do that will kill your batteries well before their time:
Fully Discharge The Battery – If batteries are fully discharged – even once – they will no longer hold a charge. Sometimes batteries are only mostly dead. In those cases it may be possible to bring them back to life gradually with a trickle charger. Usually if a battery reads 10.5-volts on a voltmeter it’s permanently dead and you’ll need to replace it.
Not Charged Fully, or not Charged Often Enough – As batteries are discharged the lead and acid reaction forms sulphate. Sulphate starts as a sludge that is easily turned back into lead, lead dioxide, and acid when the battery is charged. If the battery stays in a discharged state for too long (a couple weeks+) the sulphate slowly hardens and crystalizes on the positive and negative plates. This reduces battery capacity in the short term and kills the batteries over time. This is the #1 cause of RV battery premature death, as most RVs have lousy battery charger converters or don’t maintain their batteries properly.
Letting Batteries Dry Out – The other easy way to kill a set of lead acid batteries is by not adding water. Lead Acid batteries have vents so that they won’t explode during outgassing (electrolysis). Outgassing can happen either due to excessive discharge (high-draw 12V battery usage) or overcharging with a bad converter/charger. Lead acid batteries have vents to release excess gases and water vapor from outgassing. This lost water needs to be regularly replaced. The lead plates must be submerged to function. Exposing the plates to air will kill your batteries quickly.
Maintain RV Batteries:
Batteries are at their best when they have clean terminals, are fully charged, and full of acid. That means they should always be stored fully charged and full. That also means they should never be stored partially charged, or not full of water/acid.
That’s because the enemy of your battery life is sulfation. This is caused by lead sulfate – which is only present when your batteries aren’t full charged. Lead sulfate hardens on the battery plates and then doesn’t go back into solution, so it ruins your batteries two ways. Keep your batteries charged and this won’t be an issue.
If you have AGM batteries, then the only maintenance you’ll be doing is charging the batteries and keeping the terminals clean.
For flooded lead-acid batteries -including golf cart batteries – regular charging and occasional watering are necessary.
How To Clean Battery Terminals
Cleaning battery terminals is easy if you have the right tools. A terminal cleaning brush, a ratchet set, and some vaseline (optional) are all you need.
First – what is the stuff that forms on your battery terminals? The positive and negative terminals each tend to form their own powdery residue – but you’re more likely to see blue/green residue on the positive terminal and white on the negative.
Copper sulfate is the greenish blue stuff that forms on positive battery terminals. Copper Sulfate forms due to a reaction between the copper terminal clamp and the lead in the battery plus some outgassing from the sulfuric acid in the battery. As copper sulfate is not good at conducting electricity it should be removed when it forms. A thin layer of vaseline is a good way to prevent it from reforming quickly.
Most people are scared to touch battery terminals as getting an electrical shock is not fun. For best results always disconnect the negative battery terminal first. Make sure the terminal clamp is not touching the terminal. Then disconnect the positive battery terminal. Once disconnected, you can clean the battery terminals without worry. Just don’t touch both positive and negative terminals at the same time and complete the circuit.
If you don’t have a battery terminal cleaning brush then use any small wire brush to clean your terminals. I use a battery terminal brush as it makes the cleaning job easy.
Battery Terminal Cleaning Brush on Amazon →
How to Add Water to RV House Batteries
Adding water to your RV’s house batteries is very easy. You’ll need distilled water and battery syringe filler and about 5 minutes. House batteries have either 3 (6V) or 6 (12V) cells to fill each.
To fill battery cells simply unscrew the vent cap. Opening battery cells may require a screwdriver, although Trojan T-105s can be opened by hand.
Battery cells should typically be filled to 1/8-inch below the bottom of the lip. There’s no need to measure, just fill until it’s not quite touching the bottom of the fill tube. Make sure you fill every cell in every battery – and that’s it.
To ensure that you get the water into the battery, use a battery filler. It looks like a big turkey baster. Squeeze the bulb, stick the tube in your gallon of distilled water, fill the bulb, then transfer the water to a battery cell until it’s full.
Battery Filler Bulb on Amazon.com →
Wrapping Up
This is a relatively shallow dive into a large subject. I didn’t cover everything by a long shot! If you have questions please leave them in the comments and I’ll answer or add to this article.
Beyond that, I hope you find this article helpful the next time you think about shopping for RV house batteries!
Thanks for all the info. I appreciated it all. Question – what happens if the batteries get filled with regular tap water, and not distilled. Asking for a husband who just did that! And 3 years ago Jim posted, ” In your Series/Parallel diagram, the wording is not correct under the Parrallel photo. Should be “in parrallel” not “in series”.” It’s still wrongly worded. Thanks for your help with the water question.
Hi Lesley – if you fill a battery with tap water then the contaminants in the water (trace minerals) will attach themselves to the lead plates in the battery which reduces their efficiency. It won’t ruin the battery in the moment, but tap water will reduce a batteries lifespan and efficiency/capacity. Unfortunately you can’t get the water back out once you put it in the there.
Thanks for the heads up – I thought I fixed that, but I guess not.
Great post! I got a few questions for you. I bought a used trailer that has a solar panel and 2 6V batteries. I do not know how old the batteries are and what the exact brand/model is (it says deep-cycle Dynamic Battery on them). The solar charger is an EWC-30. I pulled out the converter and it seems to be the crappy original one. We went camping last week to an off-grid campground, so we only had the solar charger and propane. There fridge was running on propane. The only parts that used any electricity would have been the water pump and the fridge. The water pump wasn’t used during the night. In the morning, the batteries were low and I couldn’t even ignite the propane on the fridge and had to wait until the solar charger had charged up the batteries enough. My questions:
1. The batteries were obviously not able to hold the charge through the night. How do I test the batteries to see if they are still good? They are currently wired up in series.
2. How does the solar charger come into play with the setup that you are describing? The EWC-30 manual states that it has three charging algorithms (bulk charge mode, constant-voltage mode and float mode). I want to be sure that this is fine to continue to use if I swap out the converter for the IOTA one.
3. I am tempted to just toss these batteries and buy two brand-new Trojans with the new converter, but I want to be sure that it is absolutely necessary. Maybe I can save these batteries and continue to use them for a bit?
Cheers,
Timm
I have 6 6V batteries up front 2 to make 12V to start the generator, 4 to make 24V for lights. I have 8 in the back 2 blocks of 24V the back 8 r hooked up to solar. My question is I need some new batteries. can I put AGM’s up front (6) and keep the flooded (8) in the black. . Or do I have the keep the same style, AGM or Flooded
Hi Rich Thank You for the clearly explained video!! I have two 6v regular deep cycle batterie and they won’t hold a charge, Im assuming I burned them up by not filling them. Looking to replace but not sure what to go with. I was thinking AGM but don’t want to keep checking the level to see if they’re at 50%. We maybe boondocks once a moth if that for maybe a day or two. Can you please help me in choosing? I do have n onboard generator also
Hi Sam – if you want to spend minimal time checking your batteries then I’d get 6V AGM Deep cycles. They require the least maintenance and they’ll easily go you a day or two boondocking. Good luck!
Rich, I have heard that its best to replace both 6v batteries at the same time even if one is still good. Does that sound right?
Yep, that’s correct. When you wire batteries together you’re essentially making one big battery that is constantly trying to equalize the charge across all cells. If half of the cells are old or degraded (old battery), then it will impact the new battery and age it much more quickly. You’ll get the best life out of your batteries if you use 2 news ones.
Thank you for the information. My 12V batteries have died and I am looking to replace/upgrade I have a 2017 travel trailer Rockwood Roo. I was given the following information:
I have been researching your 4 stage charger and found that the 4 stage charger is not needed on AGM batteries. It is a needless expense. 2 of the 4 functions are not used on AGM’s.
1. 2000 watt inverter / charger. This will be discounted somewhat but I do not know how much. $1099.00 + $59.00 INSTALL.
2. 2 heavy duty AGM 6volt batteries. 255.49 each Install $85.68 total
3. Additional wiring needed. $270.00
4. Supplies 125.00
Total $2,149.66 plus tax.
Would appreciate your thoughts on this recommendation.
Thanks, Melissa
Hi Melissa – you’re right that AGM batteries are less prone to sulfation and therefore don’t need the equalization charge as often – but they still will sulfate over time and do benefit from equalization. Also, a smart charger is designed to charge your batteries correctly and without overheating them and causing outgassing. And Yes, AGMs can overheat and do vent, which causes a small permanent loss of capacity each time. RV Batteries are also sensitive to temperature, and should be charged at the correct voltage for whatever temp. Most are exposed to the outside, so it can make a pretty big difference. A smart charger will charge at the correct voltage vs. a fixed voltage charge will not. For more information, read this for details: https://batteryuniversity.com/learn/article/absorbent_glass_mat_agm –
As far as your install, that sounds a little pricy on the inverter/charger to me. You mention that it will be discounted, but didn’t mention the brand. The brand matters.. The price of everything else looks ok – but again,, the brand of the AGM batteries matters a lot. Do some research on battery brands. The better brands – Trojan, Crown, Lifeline, etc.. are worth the extra price as they’re more useable and will last longer. Is the additional wiring for wires from the inverter to outlets throughout the RV? Sounds pretty reasonable – I’d be curious if there’s install cost for that as well.
Thank you Rich
I’m trying to make a decision on what we need as opposed to what I’m being sold. I will double check brands.
Is a 2000watt inverter/charger necessary? Installing another breaker? Rewiring the trailer? What benefits are there from installing this?? Using a microwave??
We only use the batteries to charge electronics, run a CPAP at night and maybe a movie on the TV, water pump
water heater, fridge and heat are propane
Sorry, this decision just makes me go in circles. I don’t truly understand it, no matter how much I read through.
What are your thoughts on Lithium 12V batteries? $$$ but worth the investment?
Thank you
Hi Melissa – Even with a 2K Watt inverter you’re pushing it to use a Microwave (1800K Watt). You really don’t want to use batteries to run things that max out power draw, as that’s when batteries get hot and (potentially) lose capacity.
For me to tell you all the benefits, I’d need to know how your trailer is currently wired. Do you currently have an inverter? If so, how big is it? If you’re only running a CPAP at night and watching a movie, it certainly doesn’t require Lithium batteries (very pricey).
How long are you typically off grid? (not plugged in) If you’re only camping for a weekend at a time – overnight or maybe 2 nights, then your requirements are different than if you camp for a week off grid. If you’re plugged in most of the time when you camp, your requirements are different as well. Any info you can give me helps my reply. Thanks!
I have 2 100 watt solar panels with 2-12V battery’s. I’ve never changed the inverter/charger so I assume it’s a single stage. I rarely if ever plug in since the solar takes care of things. Recently on an October trip near Bishop Ca, the temps dropped into the 20’s and we lost battery power due to running the heater more than normal. I figured I would need new battery’s since mine are 4 years old now. Do you think it’s still important to buy a multi-stage converter? Since I never plug in wouldn’t the solar controller regulate the battery and know when to slow the charge down as it reaches full charge? I got 4 years out of cheap 12 volt battery’s using this set up with cheap 12v battery’s.
Hi Dana – You’re correct, your solar charge controller charges the batteries and (hopefully) keeps them topped off. In your configuration a 4-stage converter/charger isn’t as necessary.. and if you’re getting 4 years out of inexpensive 12-Volt Batteries, then I’d say if it isn’t broke.. – Good luck!
Thanks for the great write up. I went with your recommendation and bought the two t-105s and and the Iota dls-45. When I assembled everything I heard the batteries making a bubbling noise and that got me doing some research. I found some recommendations of supplying the batteries with 10% the 20hr amps. So a 225 system would be best charged by a 22.5 amp charger?
Being that the batteries are in series they stay 225 amp hours at the 20 hour rating right? And the iota dls is rated at 45 amps for bulk charge? That would be 20% the 20 hour rating. Any insight on this or some information to put my mind at ease would be great. The voltage is perfect but just curious about the amps. I don’t want to overcharge my two new batteries:) thanks for all the great info.
Hi Scott – The amperage of the IOTA doesn’t make a huge difference. Charging the batteries is more about voltage. It’s similar to your car alternator – it needs extra capacity to power your 12V appliances while also charging your batteries. The IOTA is charging your batteries at the same time as it’s powering lights, running fans, your furnace blower, etc.. That said, it shouldn’t be boiling the batteries. Is the bubbling noise loud?
First, make sure you have the batteries properly wired in series. You should have the batteries connected from a negative on one to a positive on the other – that’s it. Second, make sure the batteries have enough water. They should be filled with distilled water to just below the feeder tube (1/8″ below). Next – do you have a volt-meter? Check and see how much voltage the batteries are taking in. On bulk it should be 14.6 – 14.8, absorption 13.9 – 14.1, then float around 13.1 – 13.2 (depends on temp). It’s also possible the IOTA is giving the batteries an equalization charge, which is over 15V. That’s part of what the smart charger does, but it shouldn’t stay that high for very long. If you’re seeing different voltages, then the IOTA may be a bad unit. And yes, wired in series they stay at 225amp hours.
The other reason you want a 45amp unit is because that’s the most power the unit can add to the batteries in an hour (there’s always some loss). If you’re boondocking and recharging with the generator it will take twice as long to add power to the batteries with a 22.5amp unit – or longer if you’re using lights/fans/etc.. The 45amp unit is much faster/better. I’ve never had an issue with this setup and I’ve been using it for years – plus the single stage charge/converter unit that came in our RV was rated at 45amps too. I hope that’s helpful – good luck!
Does the amperage of the IOTA need to match the service to your RV? For example, my TT plugs into a 30AMP outlet, does that mean I need to buy a 30AMP charger/converter?
Hi Mark – no, those are two different things. Your 30AMP Outlet is 110/120V power in, whereas the IOTA unit is taking some of that 110/120V power and turning it into 12V power (that’s the ‘converter’ part of charger/converter). The IOTA needs to have enough capacity to run your 12V appliances while you’re plugged in (vent fans, furnace blower, lights) and also charge and condition your batteries at the same time. It’s pretty common for a 30AMP rig like yours to have a 45AMP Converter Charger. That’s how our rig was configured.
Rich, electrical systems and batteries seem to be either a black hole or a black art! There’s a lot of conflicting information out there, but I’d appreciate your comments.
We have a 19 foot trailer purchased new in the fall of 2003. We specified a 160 watt solar panel and two Interstate 6v golf cart batteries. The trailer is stored outside in Vancouver BC, and we use it about 2 weeks of the year (dry camping). During storage I check the battery water levels every month, and add water as needed, whch is infrequenty. The gear used is Carmanah/GoPower, which draws a lot of negative comment online. However, it’s now 6 years on this equipment and everything still works fine, so I’d have to say the critics have their own agendas.
Because my experience has been so good, when I DO come to replace batteries, is it really worth going to Trojans? The same again seems to be a reasonable route. We have low needs – all our lights are LED, so lights, radio, furnace fan and water pump are the only demands.
Thanks,
Nick
Hi Nick – I try to follow the rule: if it ain’t broke, don’t fix it! I’ve heard some negative comments on GoPower, but it sounds like your unit is well built and working correctly if it’s worked without issue for 6 years now. All golf cart batteries are built to take abuse – and if you’re only using them 2 weeks out of the year they should last a few more years easily. If they supply enough power for your use and they cost significantly less than Trojans then I’d stick with them the next time you replace batteries. Good luck!
I am running 4 6 volt golf cart batteries (2 in series to get 12 volts and then each series wired parallel) and have a question about how and where to connect house cables and inverter. It seems if I connect all the cables on the same series I would be using that series only and just balance charging it with the other series. Does that make sense or am I just making this too difficult – does it matter at all?
Hi James – I follow you. Yes it matters! You should have 2 sets of 6-volt batteries wired in parallel – This creates 2 double-capacity 6-volt batteries. At this point think of them as one battery each. Next you connect those batteries in series by connecting a negative on Battery Bank 1 (BB1) to a positive on Battery Bank 2 (BB2). You then need to connect the positive from the RV to a positive on BB1 and the negative from the RV to a negative on BB2. That gives you: RV+ +BB1- +BB2- -RV (just like putting two batteries in a flashlight).
Technically you can connect RV+ to either battery in BB1 because they’re wired together in parallel so essentially just one big battery (same on the other end with BB2). It’s still preferable to wire it to the battery that isn’t connected to the other battery bank in series. That forces the power to go through all 4 batteries equally and yields the best results over time.
If this is still confusing, then check out this page on battery configurations: https://www.batterystuff.com/kb/articles/battery-articles/battery-bank-tutorial.html – it shows your exact configuration toward the bottom of the article.
WE KNOW ABOUT BUDGETS. BEFORE WE RETIRED THE MOST I’VE ASKED OF MY SINGLE 12 VOLT DEEP CYCLE WAS “PLEASE LAST THE ENTIRE NIGHT”. NOW, WHEN WE HEAD OUT ITS MULTI NIGHT TRIPS. I SHOT WHAT LITTLE WAD I HAD AND BOUGHT 2 6VOLT GOLF CART BATTERIES (duracells, trojans were beyond budget friendly). FULLY CHARGED WHEN WE LEAVE THE HOUSE AND 3 NIGHTS OUT. BATTERIES NEVER FELL BELOW 11.9 VOLTS ON THE METER. AND WE HAD THE HEATER ON EVERY NIGHT. HAPPY WIFE=HAPPY LIFE
Tank you so much for your write up!
Just wondering what your thoughts are on the Trojan T145 battery. I installed 2 of them in our last motorhome and they worked great for 9 years and we boon dock quite a bit. The few more amp hours are worth it to us for the peace of mind while boon docking.
A few months ago we traded in our motorhome for a brand new 2018 model. It has a full size residential fridge that runs off of an inverter so we have a bank of four 6V batteries. On our first boon docking trip in it, the batteries discharged badly over the trip, especially over night. One morning we woke up to the house batteries at 10.5 volts so the next day we charged the hell out of them running the generator most of the day. The next morning we woke up to the batteries at 6.8 volts. This combined with the fact that I just found out from the manufacturer of the motorhome that it was on the lot for 15 months before we bought it and I know they didn’t maintain the batteries in that time. Hopefully, I can get the dealer to cover some of the costs, but I will be installing 4 new T145s soon.
Your write up on the smart converter makes a lot of sense and I think I’ll look into installing one in our new rig.
Thanks again,
Mark
Hi Mark – the T145s are great batteries too. In our case we didn’t need the extra capacity – and the T145s weigh more, and cost more – plus as they have higher capacity it takes longer to charge them. All that said – they sound like a good fit for your situation.
Residential fridges are getting increasing popular for obvious reasons, but they’re not boondocking friendly as you’ve found out. It’s helpful to do the math – I’ve read that in a 24 hour period, a residential fridge uses around 400 amp-hours(!) of converted 12V power (requires inverter) so they use a ton of power if you’re pulling from batteries.
If you have 4x Trojan T145, you’ll have 520amps of total capacity, but you should only regularly drain the batteries half way – so you’ll have 260 amps of useable capacity. That’s not enough to cover the 400amps the Fridge requires daily – let alone your other 12V usage (water pump, lights, vent fans). That means that unless you have solar power you’ll need to run the generator for a couple hours in the morning, and again for a couple hours in the evening to keep the batteries charged enough to run the fridge overnight.
It sounds like you’re ok with that solution – and yes, using a 4-stage charger/converter is a must if your RV doesn’t already have one. Adding some solar panels would go a long way too and would likely save you from running the generator in the evening (saves some gas). Good luck!
I just recently purchased a class 8 conversion . It had two large Napa commercial 8D 12v batteries as the house batteries.The weird thing is that they were wired in series which doesn’t make sense to me. There is no inverter installed any where that I can find. There is a solor system that I am still trying to understand. And there was a charging wire coming from one of the trucks alternators. Both batteries are bad so I was thinking of using 4 6v deep cycle (golf cart style) batteries wired in series/ parallel to get my 12v and a large reserve capacity. And I will add a 4 stage converter. My current TT has a converter and alternator wire but no solor, any harm in having the three sources for charging?
Hi Adam – some RVs run on 24V instead of 12V. It sounds like that may be the case with your Class B8 conversion. Double check, because lights, fans, blowers etc.. will all require 24V and you don’t want to wire in 12V unless you’re going to replace everything.
Regarding Solar – use a decent Solar Charge Controller and you’ll have no issues. It can tell when your batteries are fully charged vs. not and manage everything automatically. But again, you’ll want to verify if your rig is 12V or 24V first.
RICH, THAT’S ABOUT THE BEST SCHOOLING ON BATTERIES I’VE FOUND. WHEW, SIMPLE IS ALWAYS GOOD. HERE’S MY DILEMMA; I’M RUINED 2 SETS OF BATTERIES AND NO ONE AT ANY RV SHOP I VISITED WAS HELPFUL. I’M BUYING A PAIR OF 6 VOLT TROJANS AND A NEW 4 PHASE CONVERTER/CHARGER. I ATTEMPT TO PLUG INTO SHORE POWER WHEN I CAN TO SAVE BATTERY LIFE. BUT IF I DISCONNECT THE BATTERY WHILE CONNECTED TO SHORE POWER NOTHING WORKS. IS THIS A UNIQUE PROBLEM OR IS THIS HOW ITS SUPPOSED TO BE OR MY ORIGINAL CONVERTER/CHARGER IS JUNK? THANKS FORM THE HELP PEEWEE HENSON RENO, NV
Hi Peewee – I’m guessing that either your original converter/charger is bad – or it’s wired incorrectly. In our case while plugged into shore power the power goes to the converter/charger first – which supplies 45amps worth of 12volt power to the RV. If there are no batteries present, we still have 12-volt power from the converter. If batteries are present, the converter/charger also chargers the batteries in 4 stages. It might also be a bad fuse – some converter/chargers have fuses mounted right on them and sometimes they’re mounted on the main fuse board.
Either way, you’ll be much better off with a new 4-stage converter/charger. Good luck!
Howdy- is it difficult to start a 5500 onan with two 6v trojans?
Hi Jason – RV generators use the chassis battery – the RV starter battery – to start. Not the house batteries (the Trojans).
hey i need help i dont have a lot of money on budget just purchased a used 21ft rv i want to go to 2 12v batteries instead of one i was looking at decabe battiers says 1000 amps can you recomend a decent inverted to replace my stock one and if this battery isnt what i need could you recomend one
Hi Larry – if you’re on a budget why go to 2 batteries? I only recommend using batteries from Trojan, Crown, or Lifeline. I use 2x Trojan T105s and have had excellent results from them. I can boondock a weekend (2-3 days) between charges easily – although I don’t watch much TV. I don’t recommend other batteries simply because I don’t have experience with them.
As far as a decent inverter – I haven’t used many, but I’ve heard reasonably good things about Go Power! Inverters. Pure Sine Wave inverters are quieter and more efficient. Ideally you’ll use an inverter just big enough to handle what you need – if you’re only use 100 watts a 2000 watt inverter is overkill. Also, a larger inverter will waste more power due to parasitic loss. So figure out your max usage – and I’d probably go with either this 150 Watt Pure Sine Wave unit. There’s a link on the same page to the 300 watt unit – or bigger if you need it.
How important is Cold Cranking Amps in choosing battery? I have a 5th wheel with no generator, so don’t need to “start” anything. I currently use a 24DC with 92 AH @ 1A and Marine Crank Amps of 690.
Hi John – Cold Cranking Amps aren’t important for Deep Cycles at all – which is why they’re not recommended for Starter Batteries. CCA is largely a measure of how quickly the battery can produce power. It’s also a quick discharge that relies on the vehicle alternator to replenish quickly. You want house batteries that discharge relatively slowly as they store power better for longer = deep cycle batteries.
The 92AH @ 1A sounds like a WalMart battery. I’ve only ever seen WalMart use the @1A measure. Everyone else uses @20A. That battery should be fine if you stay plugged in, but if you go off grid I wouldn’t expect it to last long (hours). Good luck!
In your Series/Parallel diagram, the wording is not correct under the Parrallel photo. Should be “in parrallel” not “in series”.
Otherwise, a great article on batteries!
Happy travels ….
Ah – in the small text. Good catch, I’ll fix it. Thanks!
Hi Rich,
I’m thinking about putting 2 T105s in my Monarch but reading their charging requirements it says an Equalize Charge of 16.2 volts should be done monthly.
I am using a Progressive Dynamics pd9280 which is a 4 stage charger that only goes to 14.4volts for bulk charge and does not have an option for a 16.2 volt to do an equalization charge.
Do you do the equalization charge and if so, how often?
How long have you had your T105s and are they still charging to the same level?
What model of the T105s are you using?
Thanks,
Rob
Hi Rob – I’ve had our T-105s for 3 years now, and they still charge and work like new. Our Iota 45-amp Charger (https://amzn.to/2LiVcmb) is a smart charger and it hits the batteries with an equalization charge every 7 days that we’re continuously plugged in of around 15.5 volts. I’ve seen it as high as 15.7 – it varies a bit based on temperature. 16.2 volts strikes me as high. YMMV.
I’ll be replacing my R.V. battery bank with 2 -6v Trojan AGM golf cart batteries plus 1- 12 v starter battery hooked up to a 360w solar grid. Please advise me of any do’s or don’ts regarding this set-up. Are the Trojans I intend to use designed for solar power? What type of starter battery would you recommend for this application?
Hi there – Trojans are ideal for Solar Power. They’re often used in off-grid applications and do well in large battery banks – and in RVs too. The starter battery isn’t that important as it doesn’t do much. I’m replacing ours now (at 6 years) and I’ll use a similar Ford Motorcraft Battery to the one I’m replacing. Good luck!
Trojan flooded cell batteries are worth their weight in gold.
If you decide on a “string” of Trojans you are talking three or
four figures, and need to take in to account the correct cabling
(wire diameter and type), and the charging system.
With Trojans, the battery owner needs to become familiar with
using a digital voltmeter and a squeeze bulb-type hydrometer.
By regularly watering and charging a Trojan string you can
honestly expect twenty good years life from them.
I found all this out from the ‘Phone Company (remember when
there WAS a ‘phone company?) who are so cheap they can make
nickels bleed and Lincoln scream.
Keeping the terminals clean and greasy, and the battery cases
clean as well is also a path towards longevity.
Hal what charging system do you recommend and “regularly watering” is how often? I would love my batteries to last 20 years.
We have the Trojan T-105 batteries and a 2000 Watt pure sine wave inverter. We are “most timers” but seldom dry dock, usually just an overnight stay once and a while at Walmart while traveling.
We are planning a long trip soon where we may be “WalMarting” more frequently. How can I tell if these 5 yr old batteries should be replaced before the trip or if they are still are fine?
Hi Jean – Use a battery load tester like this one → (on Amazon) to check the batteries. As long as you keep them watered and use a 4-stage battery converter/charger your Trojans should last another few years easy.
It is simplest to mount your solar panels at a fixed tilt and just leave them
there.
Thanks for all the simple to understand info. We’ve purchased a Little Guy MAX trailer for delivery in April. I’m purchasing two T-105 flooded batteries, the trailer comes with a 3 stage converter/charger 1500 watt inverter, and we do some boondocking 3-5 days at a time. It will also have 100 watt rooftop solar and I will be supplementing it with a 120 watt solar suitcase. Does this system sound about right to you? We aren’t super heavy users of 110v items. Are there really no significant differences between Renogy and Go Power?
Thanks,
Dan
Hi Dan – it sounds a little short on rooftop solar. In optimal conditions – full Sun – you might be ok, but solar panel power generation drops dramatically every time a cloud covers the Sun – let alone on an overcast or stormy day. I’d recommend closer to 300 watt rooftop (3×100 or 2×150) + the suitcase and you’ll be much better off – especially during 5-day boondocking. Even if you don’t use a lot of 110v, you’ll find you use plenty of extra power with vent fans, water pump, and lights.
I’m not a solar expert, and I haven’t studied the details of Renogy vs. GoPower extensively. That said, from what I’ve read/studied, Renogy panels are very solid for the money. There are lots of solar systems that cost significantly more but that don’t actually perform much differently. The two areas to pay the most attention to are use a good quality solar charge controller, and make sure you use big enough wires (and short runs) – both from the solar panels to the charge controller, and from the controller to the batteries for best results. Good luck!
Hey Rich Thank you for writing this wonderful guidance that we can certainly use. Can you please clarify the Trojan wiring? It looks like is neg to positive, positive to neg and neg to neg is that right?
Hi Luis – not quite. You should have the negative on one battery connected to the negative battery cable from the RV. The positive on the other battery connected to the positive connection from the RV. Then connect the remaining negative from one battery to the positive on the other – that way you’ve wired the batteries in series and you’ll get one large 12-Volt battery. Good luck!
Rich,
Thanks for your reply. I really don’t want to add more rooftop as it is an LG MAX teardrop and they have to use flexible glued on panels and of course if they get hot, which they will, they won’t be as efficient. The panels also aren’t parallel to the ground because the panel follows the downward slope of the roof in the rear. So what I think I’ll do is go with one 100 watt flexible panel on the roof, and instead of the 120 portable, I’m going to get a 160 portable instead for a total of 260W. I guess it will have to do. Thanks again
Hi Dan – I completely missed the part where it’s a teardrop trailer. I think you’ll be fine with the 220W – although 260 is better. I get stuck thinking about larger vehicles – like ours – that have more parasitic loss, more lights, more 12V appliances, etc.. Good luck!
Since our current converter charger is 60 amps, do I need the Lota 55 amp charger/converter?
Hi Frank – That should work just fine. Good luck!
Hi Rich ,
Thanks for the great article, we are new to the TT world and just purchased our first one . Which battery set up would you recommend for us? We do have a Generator and will go to some hook up sites but the majority will be no hook up. Thanks
Thanks, Heber – Congrats on your new TT! As most people will tell you, it depends. In general: If you plan to watch a fair amount of TV – or other regular energy use – while boondocking, then you’ll want a 4 battery setup, or a battery bank in the 450 amp hour range. With just our 2 Trojan T-105s (250 amp hours), we can run lights, water pump, run the heat fan or exhaust fan all night (10 amp hours) and even watch a movie (25 – 30 amp hours) and we wake up with enough power to use stuff in the morning – usually still a 12.2V charge depending on outside temp. This also depends on how much space you have for batteries. Some TT mount them up near the hitch, and usually 2 is the max – but that should be enough for most people. Good luck!
Hi Rich, The best explanation in laymen terms I have seen. I was browsing this at work so I have not finished the article. So far I have not seen anything on solar. I have an old m416 trailer that I have converted with a rooftop tent and I am looking for battery power with a solar charger. Can you give me any info on this. Thanks in advance
Kevin
From Attack Trail.
Hi Kevin – thanks for that. You’re correct, I haven’t written the companion article on Solar yet. For now, a quick Google search will yield you better results than anything I can share in the comments.
Thanks for the article. Well done. Is the converter/charger swap out with the Iota as simple as disconnecting the leads from the original conv/charger and then just connecting the Iota. I couldnt find in the article if you got flooded or AGM batteries. Which did you get and why?
Thanks,
Dan
Hi Dan – I wish it was the simple, but in our case it wasn’t. Our factory converter/charger was bolted/welded on to the back of the 12V circuit board, so I had to disconnect them before I could remove the old. Installing the IOTA was easy though – just connect the battery leads and ground and bolt the IOTA down so it can’t move around and you’re done.
The Trojan T105 Batteries we use are flooded cell. I like to tinker/maintain stuff, and flooded batteries are half the cost and have slightly more power per weight than AGMs, so they work for me. As long as they’re well maintained, flooded will last just as long if not longer than AGM, so it really comes down to if you like to maintain stuff, or if you’re more a ‘set it and forget it’ type of person (and have the extra $$ for the AGMs). Either way, get batteries from a good brand (Trojan, Crown, Lifeline) and you’ll have good long-term results. Good luck!
Hi Rich,
This is a great article, thanks for posting it! We are doing a conversion of a GMC Savana, and just purchased 2 – T105 RE batteries. My question for you is about the IOTA DLS unit you are using. I’ve looked through their specs, and I can’t seem to find which voltages they use for charging. It lists them in the IQ4 specs as the maximum output of the charger. Will the DLS reach the 14.8V bulk charge that Trojan recommends? Also, it seems the float charge is 13.6V, but the recommended is 13.5V. How have you found the performance of this unit?
Because we are building this ourselves, we really want to have the right gear in place from the start.
Thanks!
Hi Darren – the IOTA works perfectly with our batteries. It runs a bulk charge at between 14.6 and 14.8. (I’ve ready 14.8 may be a bit high in reality). Absorption is between 13.9 and 14.2, and float is 13.1 – 13.2. It’s better to float at slightly lower voltage than 13.5 imo. 13.5 cooks more water out of the batteries and doesn’t appear to protect them vs. 13.2. Last – I wouldn’t worry too much about a .1V here or there. Batteries have some necessary built in flexibility due to (outside) temperature variations. You’ll also notice (if you buy the IOTA) that it charges the batteries at slightly different voltages depending on outside temperature – which is why I listed the ranges I’ve obvserved above. I hope that’s helpful – good luck!
That is super helpful, thank you very much!
I am thinking I need a 400A battery bank for the solar system I want to purchase to stay off grid as much as I want. Once I hit Arizona with my family there, we will not be in the city atmosphere at all. Are you saying I need two Trojan 6 volt batteries to replace the one I have now or do I need that in addition to the one I have now? BTW I am brand new and don’t even have my travel trailer until this weekend when we do our walk-thru and take it home. LOL!
I’m trying to understand all of this because the (expensive as hell) system I found for full solar to run most things and charge the batteries is the Go Power Solar Extreme Solar and Inverter System with 480 Watts of Solar.
Hi Richard – ok, some basic principles. All the batteries in your battery bank should be the same. The same type of battery and the same age (ideally). So if you want to run Trojan T105s, you’ll need 4 of them to have 450 Amp Hours. You can’t (shouldn’t try) to run them with a 12V battery. Mismatched batteries constantly drain/charge each other, and that ruins the batteries, hurts performance, etc.. So use all the same batteries.
As far as solar goes, you don’t need to spend a fortune to add Solar to an RV. Go Power makes nice stuff, but they charge a lot for what they sell you. You can buy a complete 200 watt solar kit from Renogy for around $300 – http://amzn.to/2GdEL89 – so there are a lot of less expensive options. The main thing is get decent solar panels, make sure you install them well (space underneath them, etc..) run the shortest wires you can, etc..
My recommendation would be as you’re heading to Arizona stop in Quartzite and get solar installed there. People in Quartzite know what you need (they’re all boondockers), and you’ll get a good price if you look, too. Good luck!
I would to see what kind of life span 6 volt batteries have my last ones were Costco – interstate and I only get about 2 years
Thanks for all the info
Hi Wayne – I’ve heard of people getting 10 years out of a set of Trojan 6V batteries. I think 6 – 8 years is pretty typical. They do need to be well maintained of course, and connected to a smart charger as opposed to a single stage converter/charge will kill any/all batteries pretty quickly.
The information here is mostly good, but there are a couple of points that are incorrect.
1. AGM batteries do not ‘off gas’. They have a catalyst inside the battery that recombines the oxygen and hydrogen back into water. http://batteryuniversity.com/learn/article/absorbent_glass_mat_agm Also, while AGM batteries do indeed cost roughly twice at a similarly sized flooded lead acid battery does, they often last twice as long in most applications.
2. Completely draining a lead acid battery, while certainly harmful to its overall lifespan, does not permanently kill the battery. Starting batteries can only by cycled like this 8-12 times before they are effectively dead, whereas a true deep cycle battery can do this 150-200 times. http://pvcdrom.pveducation.org/BATTERY/charlead.htm
Hi William – 1. You’re right that AGM batteries shouldn’t ‘off gas’, but they all have pressure relief valves so they CAN off gas during rapid recharging. Read: http://batteriesbyfisher.com/agm-batteries – “VRLA (includes AGM) batteries have a pressure relief valve which will activate when the battery starts building pressure of hydrogen gas, generally a result of being recharged at excessive voltage, typically greater than 2.30 volts per cell. Valve activation allows some of the gas or electrolyte to escape, thus decreasing the overall capacity of the battery.”
This slight loss of capacity leads to lower battery capacity over time as AGMs can’t be refilled. Even with a smart battery charger/converter you’re still liable to get some off-gassing on hot days as AGM batteries are more susceptible to heat.
Also, while AGMs commonly last twice as long as flooded lead acid batteries, that’s usually due to lack of maintenance. As AGMs require less/no maintenance they’re easy to maintain, whereas flooded lead acid batteries require regular watering and more frequent charging (if in storage). That said, a well-maintained flooded battery can and will last as long as an AGM.
2. Good info, and yes, I’ve brought batteries back from the dead before (2amp trickle charge works best) – but as you say, it’s harmful to the overall lifespan and not ideal. Thanks for your comments and info!
Great information and very clearly explained, thank you!
Excellent article Rich, would you comment on how you charge the batteries while away from shore power.
For example using a generator or solar panels, I’m looking into a similar setup.
Cheers!
Hi Steve – thanks! For context: we rarely stay off grid for more than a week, so I don’t have to worry about getting the batteries fully charged while off grid. This is important, because it’s next to impossible to FULLY charge your batteries on your generator. As long as you have a good converter like the 4-stage IOTA I mention above you can charge your batteries to 85% or so with your generator in 1 – 2 hours. If you have a single stage converter, it will take many many hours just to get the batteries mostly charged.
If you’re going to be off shore power regularly (frequent boondocking), then Solar is the only way to fully charge your batteries – (critically important for making your batteries last a long time.) In our case a 450W system (3x 150W panels) would do a good job of keeping our 2x Trojan T105’s charged (assuming we had periodic days of full Sun).
We don’t have a full solar setup, although I do carry a 100W Renogy Solar Suitcase. When we boondock, I charge the batteries to 85% with the generator in the morning and then leave the suitcase out to top them off. But again – I don’t need to fully charge my batteries, as we always go back to shore power after a week or so.
I hope that’s helpful – and good luck!
Hi Rich, nice post! I like the “12-Volt RV/Marine Flooded Cell Lead Acid Batteries” and intent to buy one for my next trip :)
Good choice, Deann!
The most complete, easy to understand article on RV batteries and chargers I have read yet! A must read for new and seasoned RV’ers alike to understand proper battery selection, uses of each and maintenance.
Thank you
Rich excellent article! You did touch in a question I have. I’m familiar and expect the 20 hr rating on the a-hr of deep cycle batteries but was knocked for a loop when I saw a 101 A-HR deep cycle batt rated @ 1 hr in walmart! Never heard of this before. Can you elaborate on this rating and how would I compare to a 20 hr rated battery of same A-HR?
Thanks!
Thanks James! The Walmart batteries you’re referring to (101 Amp Hour @ 1amp/hour ‘deep cycle’) are using deceptive advertising and will have lower capacity at a 20amp/hour discharge rate. The “1amp/hour” rating is used by no-one else, and is just a way for Walmart to advertise ‘101 Amp Hour’ capacity to people who don’t know better.
Rate of discharge (and temperature) has a big impact on total battery capacity. If you measured Trojan T-105 batteries at a 1amp/hour rate, they’d theoretically give you somewhere between 50% – 100% more total output. In fact they’d probably discharge almost as fast naturally just sitting there as with a 1amp/hour draw (slight exaggeration, but you get the point) It would literally take weeks. Alternatively, if you put a 90amp draw on my Trojans, I’d only get about 120 amps of total capacity (vs 225), or half assuming the same temperature.
From what I’ve read about the Walmart batteries, if you measured them at a 20-hour rate of full discharge (standard), they’d really have somewhere between 65 – 85 amp/hour capacity. When you consider you should only discharge batteries halfway to maximize their lifespan, that’s only ~ 30 to 40amps of useable power before you need to recharge, or double that if you have two batteries.
If you don’t boondock or use your batteries often or ever, the Walmart batteries are fine. If you do boondock (camp off hookups), and you want batteries that will last through the night, definitely get something better. I hope this is helpful, and good luck!
The 101 rating you Speke of is reserve battery capacity. Not same as amp hour rating but to convert to an amp hour rating you multiple by .4317. Basically 101 reserve minutes equates to a 45ah rating
Hi Jason – do you have a source for that info? I’d love to read it. Thanks!
so I didn’t really get why you exactly you chose the 6V batteries you did over a deep cycle or AGM 12v. What’s the purported benefit there?
Hi Fred – I’ve been told and/or read a few reasons. #1 – there’s a power advantage to wiring 2 6V batteries in series vs. wiring 2 12V batteries in Parallel. This makes some sense as wiring in series requires one less battery cable, so less parasitic loss. #2 – 6V batteries make better deep cycle batteries than 12V because the cells are approximately twice the size, so the lead plates in each cell are much larger/more dense. This also makes some sense to me. 6V batteries have 3 cells each (2V per cell) vs 6 cells in 12V battery that’s approximately the same size. last – it’s faster/easier to add water to 6V batteries (6 total cells to fill vs. 12 total). This isn’t an issue with AGM – but AGMs also cost significantly more. I’ll do more research and add this info to the article.
Hello
The Trojan t105 have about 230amp hours , a group 24 Rv deep cycle has about 75 amp hours , group 29/31 roughly 100 give or take depending on the manufacture
So right off the bat , 2- group 24 batteries are about 150 amp hours , 2 Trojan t105 you get about 230 amp hours , that’s 80 more amp hours just by using the Trojan t105
it takes almost over 3 group 24 batteries to equal (2) a set of t105’s ,
There t125, t145 , that give you even more amp hours but a whole lot more weight
That t105 is just about the same size as a group 24 Rv deep cycle battery
I have read that you shouldn’t drop lead acid batteries below 50% charge state where as the new lith-ion they can be drained to 80% of there capacity , they use to give you a chart online for life cycles and % of charge state , and anything over 50% really shortened the life spans drastically
Excellent article
Chris
Hi Chris – that all sounds right to me. Thanks for your comment!
Hi Rich. Thanks for a great article. So much I didn’t know about batteries. I saw that Amazon also sells lithium batteries. Have you ever used lithium batteries or is it not possible to get deep cycle with lithium?
Hi Mark – glad you found it helpful. I haven’t used Lithium in our RV – but as far as I understand, all Lithium Batteries work similarly (only better) than deep cycle batteries. They can be discharged 80% without damaging them, they have excellent rate of discharge, charge quickly, etc… Of course they also cost 5x – 10x as much as lead acid batteries, so let’s hope they work better!
Hey Rich. I am a first time camper owner and this was such a good read for me. I bought a used camper that had no batterues and was doing research on what is the best setup and ran across your article. I do plan on setting my camper up the same way. The question I have for you is how would I go about installing a solar system to this setup? Any information is greatly appreciated .
Hi J.T. – good question, but that’s an entire additional article. It’s on my list – but in the meantime there are many other good resources online that you should be able to find with a quick google search.
Hi Rich,
Awesome article, thanks!
I just bought a couple of T-105s for our Northern Lite camper we just bought.
Question for you…my camper came with one 12 volt battery…do I need to upgrade the existing battery wiring in my camper now that I’m going with 2 6 volts hooked up in series?
I can’t seem to find any info on this.
Standing by,
Reo
Hi Reo – Thanks! – Regarding your camper wiring: You should be fine with the same wires. Your 2x 6V T-105s are essentially just a large-capacity deep-cycle 12-volt battery. The amount of power traveling through the wires at any given time is the same, it’s just that your T-105s will keep pumping power a lot longer than your old single 12-volt battery. Good luck!