Camper Van Electrical – Battery Choice

We used to show both lead-acid and LiFePo4 battery battery choices, but prices on LiFePo4 batteries that it seems like most people will want to go with the LiFePo4 batteries. For those who want a lead acid alternative this is discussed further down on this page.

Given that you are likely going to use an Lithium battery, there are several things to consider in choosing which Li battery to use:

Chemistry

Lithium batteries are available in several chemistries, but Lithium Iron Phosphate (LiFePo4 or LFP) are near universal for camper vans. LFP have safety, cycle life, and cost advantages over other Li chemistries that make them pretty much the only sensible chemistry choice for camper vans.

Capacity

Capacity of batteries is stated in amp hours. Battery capacity for camper van systems can range from 100 amp-hrs to 600 amp-hrs. The capacity you need depends on what you are running with your electrical system, and how long you want to be able to go without charging. This page goes through the whole story on how to estimate the right size battery for your needs.

For most situations a capacity of 200 to 300 amp-hours will be good. If you want to be able to run an air conditioner on your battery with no shore power, then you may need more capacity.

Maximum Current

The specs for each battery will give a Maximum Continuous Discharge current number. This usually ranges from 70 amps to 200 or more amps. If you use two batteries in parallel, then you get the sum of their max discharge currents, so a single battery with a 100 amp max discharge current if paralleled with a 2nd identical battery ups the max discharge current to 200 amps.

You want to be sure that the max discharge current is enough to cover the current that your largest appliance draws with some margin. This is usually only a problem if you want to use a larger inverter – for example, a 3000 watt inverter will draw about 300 amps when running full tilt.

This max discharge current is set by the batteries BMS (Battery Management System) – when it sees you are drawing more than its stated max discharge current it will shut down the battery.

Single or Multiple Batteries

In the past, it was very common to buy multiple LFP batteries of about 100 amp-hours capacity each and parallel them together to achieve the capacity you wanted. For example, three 100 amp-hour batteries in parallel gives you a 300 amp-hour capacity. This is still very common, but lately manufacturers have started to offer larger capacities in a single battery. You can now buy 200, 300 and even 400 amp-hours in a single battery. Detailed review of a large SOK battery…

Personally, I lean toward using single battery with a higher capacity just due to the simplicity and less wiring. But, there are some advantages to using multiple smaller batteries in parallel. If one of the batteries fails, you are still operational at a lower capacity. Each battery weighs less and is easier to handle. You may end up with a higher max discharge current.

Cold Weather

LiFePo4 batteries have many advantages, but one weakness is that they don’t like cold weather. Charging an LFP battery below 32F can damage it. Discharging an LFP battery below -4F is not recommended.

If you know for sure you will never be operating your van in freezing weather, this won’t be a problem.

The first level of protection for cold weather operation that is offered on many (but not all) LFP batteries is a temperature sensor in the battery that senses when the temperature is below 32F, and will not allow charging. You will need to warm the battery up before it can be charged, but it will not be damaged.

The 2nd level of protection for cold weather is that the battery has an internal heater that will turn on to warm the battery up before it allows charging. There are more and more batteries offering this, and it usually does not add much to the cost – I would recommend going this way if you think you might want to operate in cold weather.

Build Quality

Most of the LFP batteries are imported, and there can be quite a bit of variation in build quality. Will Prowse and Lithium Solar do quite a bit of testing of LFP batteries including tear downs to look at build quality. Will’s put is that build quality of import batteries is getting better with time, but this is still an issue to look at – best to try and find a good review with tear down if you can.

LFP Battery Examples

This is by no means an exhaustive list of LFP brands and examples – just some ones that I’m a little familiar with…

Battle Born is a US company that offers a variety of LFP batteries of various capacities and some with heaters. By all reports they build high quality batteries and support them well. They are also expensive.

SOK Batteries offer LFP batteries in a range of capacities – some with heaters. They are China imports, but have a US presence with customer support that does respond. These are the batteries I have, so, I’m more familiar with them. A couple things I like about them are: They are user serviceable, so if a BMS goes south, you can replace it, and they have a metal case.

Epoch Batteries – offer a range of LFP batteries and have gotten favorable comments on the ProMaster forum.

Li Times – is a popular Amazon brand with a variety of LFP battery capacities and some with heaters.

There are many many more brands out there – the ones above are just a place to start shopping.

Maintenance & Care – SOK LiFePo4

LiFePo4 batteries are very sensitive to being operated correctly, but they have a built in BMS (Battery Management System) that takes care of the details of keeping all the cell voltages correct and protecting the battery from damaging by overloads, over temperatures, etc.

Like any battery, the terminals should be inspected once in a while and cleaned and tightened if needed.

LiFePo4 batteries must not be charged at temperatures below 32F.
There may be some lower temperature limit that LFP batteries should not be stored in. My personal experience having exposed my LFP batteries to -45F that it was not a problem for my batteries – YEMV.

LiFePo4 will deteriorate (lose capacity) slowly just sitting on the shelf. High temperature along with high states of charge accelerate this capacity loss. Leaving the SOK batteries at full charge parked in a hot summer location between trips is not good for battery life. I think its a good idea to at least lower the state of charge between trips to 70% or so, and if you are in a hot climate, it may be worth taking the batteries out and storing in a cooler location. There is really not enough history of use on the use of LiFePo4 batteries in camper van service to know how much of a problem this will be over time – probably best to be cautious.

Lead Acid Alternative and Lead Acid Battery Myths

It does seem like with the continuing drop in Lithium battery prices that they have become the way most people will want to go, but there is a lead acid option that still offers good performance in a camper van and the lowest price that I know of (about $200 Total!).

This lead acid alternative is two 6 volt golf cart batteries in series to make a 12 volt battery. Costco and Walmart both offer these for a bit over $100 each. This solution has a usable capacity of about 180 amp-hours, which will work for most people. This system will require some minimal maintenance, will have a life of about 6 years (if maintained). The lead acid solution will also be about 60 lbs heavier than the LFP. Some say the lead acid solution will take up less space, but this was not my experience.

There is a lot of misinformation floating around about lead acid batteries these day. I think part of this is all the people who have become Li enthusiasts since Li batteries have become more practical and cost effective.

50% Depth of Discharge

Don’t discharge below 50% DOD (Depth of Discharge). In fact, lead acid batteries can be discharged routinely to 80% DOD. This does reduce the number of cycles you get out of them, but this is pretty much true for any battery chemistry (including LiFePo4).

The chart above shows cycle life vs depth of discharge for some Trojan lead acid batteries. The red line is the Trojan six-volt golf cart battery that is used in some camper vans.

At 50% depth of discharge, the golf cart battery has a predicted life of about 1200 cycles, at 80% depth of discharge, the life drops to 750 cycles. If you go through the math, the total energy you get out of the battery at 50% DOD is almost the same as the total energy at 80% DOD. In terms of total energy out, there is no penalty for 80% DOD.

As a practical matter, if you size your battery pack to cover your worst-case scenario (furnace running, little sun, heating shower water, …) for 80% DOD, then the great majority of your cycles will be much less. So, if you size the batteries for 80% DOD in the worst case, most of your cycles will be less than 50% anyway.

So, bottom line is that the golf cart batteries have a usable capacity of 80% of 210 amp-hrs, or 170 amp-hrs. A pair of LiFePo4 100 amp-hr batteries used to 90% of their capacity gives a usable capacity of 180 amp-hours – not much different.

They only last 2 years

The Li battery sales people tend to say this. In fact it’s easy to get 5 or 6 years out of a golf cart battery if you just take care of them a little bit. Some people on the ProMaster forum have reported that their golf cart batteries are still doing OK at 8 years.

The simple maintenance is 1) adding water every few months (or at least check), and 2) keeping the batteries fully charged between trips. Lead acid batteries die if they are not kept charged while the van is sitting in the driveway between trips – solar or a battery maintainer can handle this.

Much lower energy density

This may be true in an idealized sense, but, this has not proved true in any case I’ve looked at. Our base system suggests either two SOK LiFePo4 batteries or two golf cart batteries – both with about the same usable capacity. They also both have near identical volumes. This is also true of a couple other Li batteries I’ve looked at. The increased energy density does not seem to actually materialize with the current packaging.

Venting

Many say that lead acid battery compartments on a camper van need to be vented to the outside because hydrogen gas is produced during charging and it is an explosion hazard if not vented. I’m not convinced of this and the logic for this is laid out here… You can read it and decide for yourself.

Personal Experience

I’ve had a ProMaster camper van conversion since 2014. Up until last year, I used the two golf cart solution and it worked fine. I had to replace the golf cart batteries once due to my stupidity – I let them discharge to empty by not cleaning the snow off the solar panels. Last year we switched to two SOK batteries as discussed above. I like them. Our first real trip with the SOKs was a couple months ago up to the Yukon. The SOKs performed flawlessly, but I was struck by the fact that we never did anything the golf cart batteries could not have done just as well. If I did not know the batteries were changed I probably would not have noticed the difference. I guess the message is, don’t write off golf cart batteries without having a look at them.

Gary 7/29/22, 9/23/24