Fear of car batteries

[RatherBeFishin]

Go easy on me here guys but I have a fear of a battery exploding when disconnecting or reconnecting a car battery

Instead of worrying about which terminal to disconnect or reconnect first couldn’t I tape up my wrench completely or use an insulated wrench so that it wouldn’t arc if the wrench hit the frame of the car or another metal part? Then you could disconnect and reconnect the battery in any order you want without any issues?

 

[LarryFine]

Don't be 'afeared' of us. When we chew someone out, it's (almost) always for their own good.

Well, yeah, you could, but it's not hard to do safely with a bare wrench if you think about why.

To the positive, everything else around it is "hot," but to the negative, only the positive is hot.

Thus, the negative is the safer terminal to put a wrench on with the other terminal connected.

 

[Krusscher]

I mean that would work but why not just disconnect the negative first?

 

[LarryFine]

I mean that would work but why not just disconnect the negative first?

Isn't that what I just said?

 

[roger]

Isn't that what I just said?

It seemed that way to me

 

[GoldDigger]

If you are concerned about explosion (not really a big risk compared to simple short circuits), the most likely spot for there to be hydrogen gas is in the vicinity of the discharged battery as full charging current suddenly goes through it or has accumulated in a damaged cell. So making the final jumper wire connection and the initial disconnection anywhere but at one of the terminals of either battery is a good idea, insulated tools or not.
And even when you add the additional short circuit protection of insulated tools, why not follow the "safer" procedure too.?

 

[RatherBeFishin]

I understand the logic but still always forget the order in the moment. Is there an easy way to remember which to disconnect first and which to connect first??

 

[LarryFine]

Is there an easy way to remember which to disconnect first and which to connect first??

Yes:

To the positive, everything else around it is "hot," but to the negative, only the positive is hot.

Thus, the negative is the safer terminal to put a wrench on with the other terminal connected.

 

[Tulsa Electrician]

I understand the logic but still always forget the order in the moment. Is there an easy way to remember which to disconnect first and which to connect first??

Usually in modern cars the positive has a protective cap on it and the negative usually does not.
There's your sign,
So make safe remove negative first then remove . Then reconnect first.

Plus you can always goggle.

 

[Jraef]

But… if the negative terminal of the battery is NOT connected to the cable yet, accidentally contacting the wrench in the positive terminal to the chassis will NOT cause a short, because there is no return path. Ergo to the positive, everything around it is NOT HOT unless the negative is connected.

So when INSTALLING, always connect the positive first, negative second. When REMOVING, always disconnect the negative first, then the positive. Nothing can harm you that way (unless, you lean forward and your arm slips off the fender and contacts BOTH posts… wanna guess how I know?).

 

[LarryFine]

Okay, a way to remember is this:

If you're adding a battery, + first.

If you're subtracting a battery, - first.

 

[Little Bill]

Okay, a way to remember is this:

If you're adding a battery, + first.

If you're subtracting a battery, - first.

Ain't that cute!

 

[LarryFine]

Ain't that cute!

 

[ggunn]

I understand the logic but still always forget the order in the moment. Is there an easy way to remember which to disconnect first and which to connect first??

The easiest way to remember it is to short the positive terminal, after the negative is connected, to the frame with a wrench - once. After I did that I had no trouble remembering.

 

[jim dungar]

Read the manual.
I had a Honda CX-9 that had their field installed remote start module. It required the positive terminal to be connected first.

The people designing the distributed electronic controls in automobiles may be even more out of touch with the real world than those who design websites.

 

[grich]

The easiest way to remember it is to short the positive terminal, after the negative is connected, to the frame with a wrench - once. After I did that I had no trouble remembering.

One of our old employees had a Geo Metro with a curious wrench-handle-shaped bondo patch in the fender next to the battery + terminal.

 

[GoldDigger]

Going beyond connecting + first, the detailed recommendation is to connect jumper +, jumped +, jumper -, and then for the last step connect the cable negative to a solid ground on the jumped vehicle rather that at the battery. This keeps the connection spark as far from the battery vents as possible.
Once the jumper - is connected, you do have a potential short between the cable + and cable - which is why you have solidly connected the jumped + first.