build a gmaxx and i need help

[Maxxrickard]

Why did my lipocontacts explode?
-I took my truck for a 2 min ride, not in topspeed just 2 metersruns.
-I disconnect two motor wires and the lipo contacts, with my esc still ON.
When I connect the lipo wires,PANG!! The 5.5 mm bullet contacts is very very broken.
My question is why? Did it happend because the esc was on?
What to do? I have order new lipo.