Some of our equipment, to put it nicely, is not in pristine condition so battery drain happens. We use a continuous duty solenoid (relay) with a switched ground. Everything is dead till the switch, keyed or toggle, is flipped and then the battery cable circuit is complete. The heavy duty ones look just like an old Ford starter solenoid. For car/truck use the relay could be mounted anywhere along battery cables and just 14g run to the switch. The hot wire to the relay is the only circuit that stays hot so drain is unlikely.
