fire cracker bang

[beyondbuild]

98 ds. OK, got it charged up(individually charged batteries to 51 volt total)with probable bad obc. New motor with alltrax 300 programmable (indicator light not showing anything), all wiring quadruple checked to schematics, rapped ape - lost my hat - for about 30 seconds of big grin. BIG BANG. blew off a battery cap and a little mess in the pants. that battery is down a couple volts, others maintaining. No heat or smoke found on parts or wires. so what??