Situation:

Volvo 940 (I think), almost 20 year old.

We need to disconnect the battery while it sits 2 month, 3 month or 6 month.

Else the watch or something different drains the battery.

How do I explain that process to my wife???

I was thinking of:

open the minus, disconnect it.

Than open the plus and disconnect it.

Connecting:

First connect and screw the plus

Second connect and screw the minus.

Right????

I thought it isn't easy to open plus first because if you touch anything with the tool you have a short.

Reverse for installing.

Disconnect the earth first, reconnect the live first. I do this and am still here.

Disconnect the earth first, reconnect the live first. I do this and am still here.

Isn't there a case for disconnecting the live first and reconnecting it last. If no main earth then reconnecting the live without a main earth could mean that any tiny earth ... damaged wire covering etc ... would mean all the current goes to earth that way and doing quite some damage ... just a thought.

Edited April 20, 201214 yr by JAS21

Disconnect the earth first, reconnect the live first. I do this and am still here.

Isn't there a case for disconnecting the live first and reconnecting it last. If no main earth then reconnecting the live without a main earth could mean that any tiny earth ... damaged wire covering etc ... would mean all the current goes to earth that way and doing quite some damage ... just a thought.

You could be right.

The reason for disconnecting the "-" or earth first is more of a practical matter than anything to do with electronics.

It is a safety precaution against touching another part of the car with the tool, and causing a short circuit which can be spectacular with the amount of energy stored in a car battery, while it is touching the battery terminal.

Electrically it doesn't make one bit of difference which one you disconnect first, either wire removed the battery terminal presents an open circuit.

For the OP - just remove the "-", or whichever wire is connected to the car body.

Yep! Disconnect Minus first. The reason is that you won't make a short with your tool when coming to chassis. ( Possible when you disconnect Plus first and your tool connects with Minus of your chassis)

When connecting it again, please Plus first, as you can't make a 'short' when you come to the chassis with a tool when Minus isn't connected.

Thanks!

exactly what I wanted to do....shorts can be pretty spectacular.......

Can somebody please clarify why is it necessary to disconnect both (-) and (+) cables of the battery? Wouldn't disconnecting only the cable which is connected to the car's chassis (earthed) be enough? I have two cars which I alternate between Winter and Summer use. In both cars the negative (-) cable is connected to the chassis. I disconnect only the negative cable, and leave the positive (+) cable connected to the battery. Been doing this for the past 20 years without any problem.

Can somebody please clarify why is it necessary to disconnect both (-) and (+) cables of the battery? Wouldn't disconnecting only the cable which is connected to the car's chassis (earthed) be enough? I have two cars which I alternate between Winter and Summer use. In both cars the negative (-) cable is connected to the chassis. I disconnect only the negative cable, and leave the positive (+) cable connected to the battery. Been doing this for the past 20 years without any problem.

You are absolutely right. Disconnecting the Earth, Ground, - or negative terminal whichever term you may use is all that is necessary. Just make sure the cable can't spring back towards the battery post. Tuck it behind something so it won't move.

Can somebody please clarify why is it necessary to disconnect both (-) and (+) cables of the battery? Wouldn't disconnecting only the cable which is connected to the car's chassis (earthed) be enough? I have two cars which I alternate between Winter and Summer use. In both cars the negative (-) cable is connected to the chassis. I disconnect only the negative cable, and leave the positive (+) cable connected to the battery. Been doing this for the past 20 years without any problem.

You are absolutely right. Disconnecting the Earth, Ground, - or negative terminal whichever term you may use is all that is necessary. Just make sure the cable can't spring back towards the battery post. Tuck it behind something so it won't move.

hmmm...this is starting to drag....here is info from some other source :http://www.ehow.com/how_7147181_disconnect-car-batteries-storage.html....BTW,I agree with the (-) first to be disconnected as well.

As others have mentioned, you only need to disconnect one cable only, + or -, doesn't really matter. However keep in mind that every battery will self discharge over time. Some battery types discharge faster than others. How long your battery will last even disconnected would depend on the battery age and charge level (probably battery brand too) before disconnecting.

In my pick ups in Canada I have no problem leaving them disconnected for 3-6 months and sometimes longer.

Why not fit a battery isolator switch to the positive side?

Easy to switch on and off.

http://goo.gl/XJi7J

Why not fit a battery isolator switch to the positive side?

Easy to switch on and off.

http://goo.gl/XJi7J

Yeh, l had that on my little used Pontiac. As well as a trickle charger, 2 batteries in over twenty years.

thanks everyone.....

Yesterday the car broke down...most probably the generator dead.

I just changed the battery because I thought the bat is dead......

2500 Baht new battery

2500 Baht pick up the car from nowhere

don't know how much the repair will cost, not much I guess....

At least maybe I can save money feeding myself on grass, kwai as I am.....

(I wouldn't blame myself if I would a 18 year old girl, but in fact I am a middle age man with a degree in engineering and theoretically able to fix everything myself)

h90:(I wouldn't blame myself if I would a 18 year old girl, but in fact I am a middle age man with a degree in engineering and theoretically able to fix everything myself).

After reading your post on a basic lead acid battery I am glad you added "theoretically able".

Ps: You didn't happen to work for Ford Australia when the original XK Falcon was on the drawing board?

Yeh, l had that on my little used Pontiac. As well as a trickle charger, 2 batteries in over twenty years.

that's what i'm looking to buy for a car which is used only on weekends for an hour or two.