By Greg Illes
Battery capacity is a common topic among RVers, with much discussion of LED lighting and various power-saving techniques.
But less understood is the specter of battery life itself: Batteries “die,” which typically means they won’t hold a charge or deliver rated capacity. When this happens, the checkbook comes out and the price tag can be startling. Even a modest two-battery complement is $400 or more. If you’re an AGM (absorbent glass mat) advocate (and there are good reasons to be so), then up that price 50 percent. High-capacity setups are high-priced setups.
Some folks get good service from their batteries — five years or more. Others seem to be unlucky and find replacement necessary in as few as three years. In fact, battery life is not about luck — there’s a lot that you can do to extend the useful life of your coach batteries, perhaps by two or three times. Several influential factors are under your direct control.
For flooded-cell batteries, always keep the water at the proper level. Poor water maintenance is one of the biggest killers. (Sealed AGM batteries don’t have this issue, and don’t have corrosion issues to deal with — but are much more expensive.)
Battery life varies by a factor of ten with discharge level — fully discharging a battery creates the shortest lifespan. Don’t discharge your batteries below 50 percent of capacity. By far the best way to measure this is to check battery voltage under a light load. The 50 percent level is 12.0V-12.2V for most batteries (but check your manufacturer’s specifications). Sadly, stock battery-condition instrumentation in many coaches is very inaccurate. Use a good voltmeter or install a built-in meter.
Partially discharged batteries have a much higher tendency to sulfate and degrade. Keep your batteries fully charged when stored or parked. Remember that even a disconnected battery has a self-discharge rate and needs charging even when not used. Use a trickle charger, or a three-stage charger to prevent overcharging damage due to heat and water loss.
All batteries eventually experience sulfation. This is where normal-operation sulfates become crystalline and cannot be reabsorbed. A desulfator can help break these sulfates down and restore battery health. These affordable units also maintain charge, and can be hooked up during storage.
It takes some diligence, but you can easily double your effective battery life with the proper attention and care.
Greg Illes is a retired systems engineer who loves thinking up RV upgrades and modifications. When he’s not working on his motorhome, he’s traveling in it. You can follow his blog at www.divver-city.com/blog.