That's a good point. Some of the wall chargers put out AC and some put out DC. The ones that put out AC relied of course on there being a diode(s) on the battery side of the connector....Another thought, did the old battery possibly have a rectifier attached which changed AC to DC, and the new battery doesn't? That's the only thing I can think of causing the new charger to blow.
(I found that out the hard way rigging chargers from one brand to the other on the old B&D and Disston rechargable grass shears of years past. )