Hey all, Maybe someone out there can help resolve this once and for all. When putting a car in for long term storage or when replacing a starter for example,should you disconnect the pos. or neg. cable from the battery? My friends and I always disagree on this,so on this topic majority will rule and end it once and for all.
Thanks.
JIM
You always disconnect the negative first and connect it last, no matter what the reason for dis/connecting.
The reason for this is simple: the negative pole is also connected to the body of the car, so effectively the whole of the body is a negative pole. Were you to disconnect the positive first, there's a chance that during the procedure the spanner completes a short circuit between the positive terminal and any metallic part of the body, i.e., the equivalent of simply connecting the two poles of the battery with a spanner. If you disconnect the negative first, there's no chance of this.
The negative one is the safest to disconnect.
If you only unhook the positive, you can theoretically, hell no, actually drop something or turn a wrench that is touching the body onto the positive post causing a dead short to the battery and massive spark and maybe explosion. (batteries do explode if they have been recently charged or discharged and are exposed to spark)
If the negative is off and you touch it with a grounded wrench, you only should get a small spark from the milliamp draw of the radio and computer holding power. If you hit the positive with the negative cable off, nothing happens.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Technically speaking, it doesn't really matter which one is disconnected.
However, when you disconnect the battery, you should FIRST disconnect the ground lead. This is because you can safely remove the ground lug without worrying about your wrench striking the chassis and arcing over.
Then you disconnect the positive lead. Since the ground has been disconnected, you can safely strike the chassis while doing it.
So you have two choices:
The first one is a lot easier to do.
--scott
If the only consideration is "open the circuit", then which cable gets pulled off the battery is *TOTALLY* irrelevant. From a practical standpoint, it's wisest to disconnect the ground cable first. (For modern cars, that would mean the negative cable in every case I know about. For pre-1950-ish antiques, it could be either the negative or the positive, depending on the specific year, make, and model)
The reason: As long as the ground cable (regardless of whether it's the positive or the negative) is connected, the *ENTIRE BODY* of the car is an extension of that battery post, and unless the battery is totally dead - And I mean *TOTALLY* - any contact between the hot and the body
*WILL* result in an *ABSOLUTE MINIMUM* of a nasty spark, probably a hickey on your tool, likely a hickey on the car where the contact was made, perhaps a burn to you, and if your luck is truly out that day, might even result in a full-blown battery explosion. (Definitely NOT something you want to experience from anywhere closer than several hundred yards away) Making contact between ground and the body is a complete "so what?" concept in every case, since it's already connected to the body. How can "connecting it some more" cause problems? Answer: It can't, and it won't.If you want overkill for long-term storage, feel free to disconnect them both - but be sure to pull whichever cable is "ground" FIRST so that you don't short the battery through the body while wrenching on the hot terminal to get it loose.
Hey, Scott, I believe the 2nd option should be avoided due to reasons in
1st 2 replies. Your 1st choice is definitely preferable. sYes. It's better to disconnect the batter for long term storage. It reduces the chances of the battery dischaging through the leads.
However it might not be a good idea to remove the battery from the car. I did that once on a car I wasn't going to use over the winter. I brought the battery into the house and left it in the basement. In the spring the battery was dead. A battery will discahrge slowly even if it is disconnected from the car. A warm better will discharge faster than a cold battery. I should have left the battery in the car out in the unheated garage. I still don't use the car much in the winter but I leave the battery in the car connected. I hook up a cheap second hand battery charger once a month in winter for an hour or two to top up the charge.
Hope that is what you were looking for.
Do both. Then you and your friends can spend time on something else.
------------- Alex
Always a good idea to disconnect both, that way you have almost no way of getting in trouble. And it will give you an opportunity to inspect the terminals and clamps for oxide build up.
Doesn't matter if you disconnect the positive or negative, but you should disconnect ONE or the other in order to break the circuit so that you cant short out the starter terminal with a wrench when changing the starter (200 amps through a wrench isn't pretty, and your palm may wind up branded "Craftsman" if you can't let go before the wrench heats up a few hundred degrees).
For practical purposes, its safer to pull the NEGATIVE terminal off the battery for the same reason- so that the wrench you're using on the battery terminal won't form a short circuit if you accidentally touch the car frame while disconnecting the battery cable.
If you use a disconnect switch in line with the battery cables instead of actually pulling a cable, you can the switch in the positive cable and use it without fear of an accidental short circuit. From the circuit point of view, you can break the circuit on either side. Its purely a safety issue to pull the negative cable first and install it last when connecting or disconnecting a battery from a car.
Why couldn't you have used the cheap battery charger on it when it was in the house?
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.