ECM etc draws enough standby power to make battery low
in 1 - 5 weeks.
Normally is not a problem But Freezing Weather can freeze the low battery.Can a Car Battery Freeze?
Google: car battery freeze temperature
Battery does not care what term is pulled... As above, Neg term first won't dump 200+ amps when your tool hits the frame.
If you have power then battery tender et al can help. Just connect the charger and leave battery cables alone.Warning: Most should not use any charger outdoors for storage.
Even if wiring is 100% good and charger is out of weather because the cable(s) can be a tripping problem, cut by snow shovel/blower, etc. If that doesn't kill anyone, You could get sued for this and Insurance might pay then cancel the policy. (No Home insurance means big trouble for your mortgage.)
If car is outside then pull battery and take inside and charge if needed. Inside storage (Temp > 50°F) for the battery doesn't need a charger connected all the time.
------------------Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)The Ogre's Fiero Cave
[This message has been edited by theogre (edited 11-30-2015).]