Basic battery guidelines

The post Understanding batteries, start with these links will set you on a path to learn anything you might want to know about your RV storage batteries. But if you just want to know what it all boils down to, here are a few rules of thumb that may serve as a guide.

1) buy batteries intended for the way you plan to use them from a retailer who sells a lot to folks that use them like you do and will stand behind what he sells.

2) cycle your batteries down at least 10% to no more than 50%. For a 12v system this means the battery voltage will be between 12.4v and 12.0v after resting for at least a half hour with no loads or charging. This makes sure the batteries get proper exercise to stay in good condition.

3) plan on about 1 pound of battery for each 10 watt hours of energy you need for a typical 3 day weekend.

4) always recharge your batteries promptly, properly, and vigorously with a 3 stage charger rated to provide about 20 amps for every 100 amp hours of battery.

5) never let batteries sit without a full charge.

6) if not using your batteries for more than a couple of weeks, use a battery maintainer that will keep them fully charged and apply techniques that inhibit sulfation.

Modern RV use can be rather hard on batteries. There is often a one or two amp constant load to run the refrigerator control board, the alarms, and other resident loads. This is enough to run down a typical group 27 sized RV storage battery in a matter of three or four days. Watching a DVD movie in the evening can take 150 watts for three hours. That 450 watt hours needs about 45# of battery (guideline 3 above) which is near the weight of a group 27 battery. That current drain is also a steady drain at about twice the rate at which the battery capacity was calculated. Those two factors add up to reduce expected capacity another 20% or more.

Just sitting out of use is also hard on RV batteries. That is why devices like the BatteryMinder or the Progressive Dynamics converter with the Charge Wizard or the WFCO converter work well (links to Best Converter sales pages). These all keep the battery full charged and the electrolyte mixed to inhibit sulfation and sulfation is the major cause of death for RV batteries.

7) let your own experience be your guide. If you keep running down your batteries either enlarge your battery bank or change your RV lifestyle. If your batteries don’t have the life you expect (5 years or so for the typical RV battery in typical use) then change how you use and maintain them.

There are many posts in this blog about batteries (link to search results). Some folks get obsessive in watching and worrying about their batteries. It can make a nice hobby but don’t let it get to you. See the posts on hydrometery and measuring battery status. If you let experience be your guide and just keep an eye on the resting voltage, you can do well enough. That means you can put your attention to enjoying the RV experience without excessive worry about the RV systems.

1 Comment

  1. AGM batteries - Airstream Trailer & Motorhome Community said,

    May 31, 2008 @ 2:45 pm

    […] lifespan of most RV batteries is a lack of attention to proper charging and storage management. See Basic battery guidelines for some ideas on this. __________________ […]

RSS feed for comments on this post