RV BATTERIES IN A NUTSHELL
So it’s time to change out your “house” RV batteries (the batteries that run your trailer, fifth-wheel, or motorhome’s lights and appliances, not the ones that start your motorhome engine). What are your choices? It’s kind of complicated, and can require some research or help from your battery store, but here are the basics in a nutshell, to get you started so you can ask the right questions…
Let’s look at RV battery types.
Flooded batteries: Lead acid batteries. These are the least expensive, but require you to check the water levels in the flooded cells to make sure they are covering the lead plates. They also need to be vented for gasses they release when charging.
Sealed / AGM batteries: Also lead acid, but the cells are sealed so they don’t require water to be checked, and they don’t need to be vented like flooded cells. But they are a bit more expensive.
Lithium: Super light, sealed cells that can be placed just about anywhere. They are significantly more expensive, but can be run down 80 – 90% without damaging them (as opposed to 50% limit for lead acid) and have a longer life. Be aware that they can require some adjustments to your DC system, like the proper converter charger. Ask your battery manufacturer or expert more about this if you are considering them.
Other things to consider…
Deep cycle: You want a deep cycle battery for your house batteries. Batteries for your engines are designed to release a lot of energy quickly, then your vehicle runs off the alternator. For your house lights, you want a battery designed for small release of energy over a longer time. If you have only one battery for house and motor, they do make hybrid batteries (sometimes called marine batteries) that are a compromise of both.
6v batteries: If you have lead-acid batteries in pairs (2, 4, etc.), you might consider 6v batteries. Generally designed for things like golf carts, which are constantly draining and recharging, and are bounced around a lot, they are a good fit for RVs. Their thicker plates can take the abuse of travel and hold up better for long slow power draws. But your system is 12v, so how do you use 6v batteries? It is very simple, it just requires connecting the batteries slightly differently. 12v are wired parallel, whereas 6v are wired serial.
Here’s a link to a battery guide that explains this simple wiring more thoroughly.