Exploding coach battery!

I had a coach battery blowup when our coach was no more than six months old. I called Forest River manufacture. There warrenty department manager told me to thoroughly wash down the battery compartment. He then had A dealer bring out A pair of new batteries and had them check out the converter/ charger to be sure it was not overcharging. We also stopped in at the factory Service Center on our way Home from Texas that spring. They checked out the charger and also found out it was okay. They then decided it must have been A defective battery. The coach is now three and a half years old with the same batteries and they are fine.