RV Batteries 101 & Why we use Trojan T-105 6V Golf Cart Batteries in our RV - Trek With Us (2024)

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.

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 Charger / Converter

Right after upgrading our batteries I replaced our single stage converter with an IOTA-DLS45 4-Stage Smart 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 aboutshopping for RV house batteries!