Battery Disconnection... "+" or "-" first

[montgomery]

We were have a discussion at training this morning about disconnecting batteries on cars. There were pros and cons stated for both disconnecting the positive first or disconecting the negative first.

We agreed that most thought the negative should be disconnected first. But a point was raised that if the negative was disconnected first, there is a risk of it grounding on something.

Any ideas???

Thanks

[lutan]

We teach t odiscinnect the "earth" lead first. ie: the lead that when traced back, will be connected somewhere to the car body or the engine block.

Generally, in Australia, our cars are negative earth, but on some earlier model cars, it is a positive earth.

Whilst disconnecting batteries, we also teach to discinnect the battery terminal. Some operators like to cut the lead, and to also cut a section out of the lead so as there is no hope of re-connecting the lead to the terminal. The downside to this is cars with full electrics. It may be necessary to have power to the car move seats back, up or down to assist with extrication, yet if the lead is cut, it can not be done.

Hope this helps....

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[R.G. SMITH]

We have always been taught to disconnect the Negative First as well. As to your question on how to prevent the Negative from unintentionally grounding, I have been taught two ways: The first is to cut the negative in two places, so it is not long enough to contact any metal. The problem with that is if some reason you would like to re-connect the electrical system,(maybe to put the car in neutral, or move the electric seats) you won't be able to.
The other method I have been taught is to take electrical tape and bend the wire onto itself and tape it, now it is too short to ground anything but can still re-connect to the terminal if need be.
I hope that this helped some

[Nick SBFD 6]

The chances of the ground wire "grounding out" I.e.; setting off the airbags are remote, but if the positive hits the ground and sparks, fire or worse happen. then you have larger problem on your hands. Our department ALWAYS disconnects the negative first, and we also prefer to disconnect rather than cut. Power convertible tops and seats can be a valuable tool during extrication.


-Nick

[Squad15]

Disconnect the negative first. When disconnecting Pos. first you may accidently touch ground and create a shower of sparks. This poses the risk of starting a fire or causing injury to the person disconnecting the battery.

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