floating ground = shock & fire hazard
 

When you get downrange, one of the first things you do is start outfitting your vehicles. One quick word of advice coming from an EMS guy - when connecting 12 VDC devices to a battery in a vehicle that has a multiple battery system, make sure you connect it to the GROUNDED battery. If a device is connected across the ungrounded battery, you will have a 24 VDC potential between the chassis (ground) of the device and the vehicle ground. If the device happens to have a metal chassis, there will be serious fireworks going off when power is applied and the device may be destroyed, the vehicle generator (alternator) may be damaged, you might get a nasty shock, the battery might violently vent or a fire may start.

Nobody wants to lose equipment or a valuable trigger puller due to an avoidable circumstance. Your thoughts are welcome.