I'd be surprised that there aren't safety systems built in the hybrids like those in the HID lights to shut it down. Even so there are fuses and batteries are still quite heavy so the battery box(s) are quite sturdy built so in a worst case accident the battery box should still stay intact and a fuse will pop if a wire shorts somewhere. I was in a shop when another tech popped a fuse in a big UPS while changing batteries (he hooked them up backwards because the UPS maker decided to use red for - and balck for +). A 300A fuse blowing makes quite a loud pop and your mental reaction makes you feel like you have just been electrocuted even when you haven't.