Friday, June 9, 2023


Why is RV battery bank leaking electrolyte?

gary-736Dear Gary,
I have a 2002, 31-foot Jayco. Why is my battery bank leaking acid? I have two batteries and two solar panels with a PWM charge controller. When we bought it, it was hooked up to power; now we keep it stored. One battery was leaking in the first two months so we replaced both batteries. Now, a month later, it’s leaking again.

The only power we see on in the fifth wheel is a clock on an entertainment center which we can’t power off, and a green light on the LP gas detector. We also found a horizontal crack on the side of the wall half-way up above the hitch about 8 inches long and 1/8 inch or less wide. Can this cause internal water damage? Should I patch it? BTW, I’m a first-time RVer. —Lisa

Dear Lisa,
I’m assuming the batteries have been inspected for physical cracks in their casings. It is entirely possible the battery bank is not receiving the proper charge rate and is being subjected to overcharging, thereby boiling the electrolyte. It will be necessary to perform some diagnostic measurements before, during and after charging the bank, I’m afraid.

It is crucial that the PWM (pulse-width modulated) charge controller be configured to an algorithm that is beneficial to the specific batteries in your battery bank – one that will fully charge them yet not exceed the gassing voltage during the charge cycle. I’m guessing the charging voltage might be set too high and a continued overcharge by the solar system is taking place. Or it may be set for AGM batteries rather than wet cell batteries.

I wish I could be of more help, but to ascertain exactly what is transpiring, some specific measurements must be taken. I’d suggest a pro (certified) RV service technician take a look to see what’s going on.

And yes, any opening into the roof, sidewalls, front or rear of any RV is an open invitation for water intrusion. Water intrusion is the number one cause of RV damage and can lead to very expensive restorative repairs if not addressed soon. So, indeed, have that crack repaired as soon as possible! Even a temporary fiberglass patch is better than leaving it open until a professional repair can be made. And welcome to the RVing lifestyle! 

Read more from Gary Bunzer at the See Gary’s videos about RV repair and maintenance.




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