Connecting Batteries Safely

[Jim P]

When connecting the battery, what's the safest way to tighten the connectors? At some point in the process, something is going to be hot and there's the arc risk.

Jim

[ptrotter]

Connect the positive side first. That way if you hit the airframe with your wrench, it is not an issue. Then when you connect the minus side, you only have to be carefull not to hit the positive terminal itself.

[DanH]

Jim,
General rule is "Negative off first and on last".

Principle is simple. Swinging a wrench and connecting negative to structure is harmless; doesn't matter if the positive is connected because you did not create a circuit. Swinging a wrench and connecting positive to structure will arc if the negative is connected because the structure is grounded. So, remove the negative first to un-ground the structure. Connect it last because doing so is harmless.

None of this will save you if you swing a wrench against the other battery terminal. In the car business we buy or make a wrench with an insulated handle because people sometimes do dumb things. The other trick is to hand out wrenches with handles too short to reach the other terminal, but insulated is better.

[Canadian_JOY]

My toolbox contains a wrench wrapped in electrical tape. That tape's been on there since 1985, during my first week as an apprentice AME (Canuck equivalent of A&P). Lesson learned the hard way, and never forgotten!

[tomwebster]

Years ago, I was taught to connect the ground post last.
I think it still applies.
Tom