The new battery in the TT I bought 2 weeks ago also exploded (top case failure.)
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The seller told me that it was a new battery and it does have a "4/13" stamp on top of it, but when I removed the battery box cover, both of the caps for the cells were off and the top of the case was cracked.
On my 89' Layton, I do not believe there is a "float mode" on the power inverter/converter and I know the seller had it plugged in for a LONG time, maybe several weeks.....so I suspect that due to the fact that this is an older trailer with no float mode, he overcharged the battery, cooked all or most of the water out of it and it exploded. NO damage, not even to the plastic battery box, but it's unfortunate becaue I now have to buy another battery for it!
Unless it just had a bad case, I'm almost tempted to call Walmart and see if they will make good on it since it's so new!