Winter time means the trailer sits idle for a few months, at least up here in Minnesota. That idle time can take a toll on the batteries. In the summer between trips is also a time to worry about the battery charge. Our solution is to use a battery maintainer.
Why use a maintainer? Deep cycle batteries can be damaged if allowed to drop to zero voltage. The maintainer measures the voltage and slowly charges them back to a full capacity. It does not replace the need to monitor the water level in the batteries. The photo below shows the water level in a battery needing to be topped off with distilled water. While on a maintainer, the batteries should be checked about once a month for voltage and water level. Be very careful opening the top of the battery. What starts out as distilled water becomes sulfuric acid in the battery.
There are many manufacturers that make battery maintainers. We choose one that has circuitry to not overcharge the battery and to keep it at a constant charge. Currently we have two maintainers, one for each battery.
When we winterized the trailer, we removed the batteries from the trailer tongue and moved them to the basement until we prep for the next season. Our plan is to move the maintainers out to the trailer and use them between trips. This will mean removing the batteries from the trailer circuit by adding a disconnect. [This will most likely be a future post on this blog.]
A good article regarding RV batteries was in Trailer Life in June 2017 (https://www.trailerlife.com/tech/understanding-and-maintaining-your-rvs-batteries/)
While doing some research for this post, we discovered that our maintainers were not rated for our batteries. The maintainers go to 40 Ah and the batteries are 65 Ah. After checking with the maintainer manufacturer, we learned that the only issue with the lower rating is that our batteries will charge very slowly taking over a day to reach full charge. With our use, these will work, but if we were purchasing again, we would choose a different model.