I have a slightly dodgy bettery (or terminals or something) so it runs down if unattended for a while.

To avoid flatting the battery while away from home I was going to leave the battery disconnected while I am away. I know you have to disconnect the negative first and then positive.

Is it OK to leave it with just the negative disconnected to break the circuit or should the positive also always be immediately disconnected?

 

Also I read that you must never let the positive cable terminal touch any part of the bodywork. Since the negative terminal is disconnected first, then, by the time the positive is disconnected the battery will be unattached to the car so why does it matter so much about the positive terminal touching the bodywork? (or did this warning only apply to the situation where you have incorrectly disconnected positive first and the negative is still connected?)

 

You know wrap them both in electric tape and end of discussion lol. Want a beer?

 

On a side note if your going to be away and if possible just have someone drive your car once a week for 20-30 min that keeps the battery charged due to the alternator charging it back up. If you don't have that option yea unplugging it is fine.

You can just unplug the Positive (power/red/+) and wrap it in electric tape and cover it and your done. If your karma wants to unplug them both feel free to my knowledge I don't see it draining it if the positive is undone. I've done that all the time with my FORD Expedition (to reset the cpu mainly) it works fine and jag is pretty much a ford knock off.

 

mojorising, the reason why you will find most people recommend disconnecting the negative post first is that when you are using the wrench to remove the terminal clamp, if you slip and let the wrench touch both the battery terminal and the body, you will see nothing. If you do the same thing with the positive post, major arc and spark show (TRUST ME!!!!). If you are going to be letting the car sit, all you need to do is disconnect the one lead. Tuck it out of the way or as Kris said, wrap it in electrical tape.

 

There is actually a much larger safety reason, but related. If there are sulfuric acid fumes present and an arc is created it can ignite these fumes and explode the battery. This can cause serious bodily harm as you'll likely have your face over the battery frontal area.

http://www.vinland.com/Car-Battery.html

Personally, I like to keep the car electronics active with a battery tender on a trickle charge. That way you keep all settings in non-volatile memory active.

 

Just make sure you're able to get back in afterwards. I read of someone who parked their car in the garage, had to climb out of the passenger side as the drivers door was right against the garage wall. They popped the bonnet, closed and locked the door. They then disconnected the battery and closed the bonnet.

This left them unable to use the remote central locking to unlock the car and they couldn't open the drivers door either because it was too close to the wall. All other locking mechanisms (central locking and boot locking) are electrically operated - leaving them unable to open the car to pop the bonnet to reconnect the battery...

Not sure how they resolved it in the end...

 

Ok stupid question - where are the vents on batteries. I'd assume toward the top middle or sides flaring out.

 

QUOTE FROM VINLAND
5. Attach the other end of the black cable to the engine block of the car with the dead battery. Look for an unpainted metal surface and make sure the cable will clear anything moving when the car starts.

6. Do not attach the negative cable to the dead battery since it will spark!

Um, where in the world are you gonna put a clamp on the engine block (considering its covered in plastic)? I assume he meant engine bay?

 

Steve11, disconnecting the positive or the negative terminal in relation to arcs is irrelevant. When you make/break an electrical circuit, it will make an arc (now, whether it is visable or not is another issue). The current at the positive post is the same as that at the negative post. So, either way, you will get an arc. Other things play in at that point, hence why I point out the reason to remove the negative first.

As for the vent, if you look on the top of the battery, you will see a small tube coming out the side of the battery at the top/center. This feeds into a tube in the battery box which then vents the fumes out of the box, reducing the chance for an explosion. Not all batteries have a vent to them as about half of the new batteries made are "maintenance free" and will not have a vent as they keep the gases inside the battery so they can recombine and maintain the water level.

 

If you do disconnect the battery while you go galavanting, you're going to have to re-program your one-touch window-up buttons. (From a Brutal Post: "to reset window one touch. Raise and lower each window 1 at a time. At the raise and lower postion press or light the switch and hold for 5 seconds to reset the limits in the modules for one touch to operate again.") Your kitty may "forget" other stuff too.

Maybe you should just spring for a new battery - Ol' man winter's coming, and you dont want to be that guy in the DieHard commercial cussin-n-fussin.

 

Thanks to all for advice.

If it is OK to just disconnect one terminal which one would you disconnect? Positive or negative (I am guessing negative since it is supposed to be disconnected first and reconnected last?)

I have disconnected the battery before (both terminals) when away and all I lost AFAIK was the one touch windows but I knew that was going to happen.

Just my opinion but seems weird that car manufacturers let the CPU memory settings rely on the car battery to hold memory. Even my mobile phone has a backup battery to remember settings. Seriously, has a backup battery system never occurred to anyone in the car industry?


Not in Sydney it's not. Went snorkelling and saw a stingray today

 

You can get a battery cut off switch if you want:
http://www.harborfreight.com/battery...tch-92688.html

It does not matter which terminal you disconnect but as been said, the negative one
is the safest to remove.

Last, it is not sulfuric acid fumes that cause a battery explosion it is hydrogen. (think HINDEBURG!) A by product of lead acid batteries is Hydrogen and that is what can casue an explosion.

My vote is to just get a new battery--$79 at Wa-Mart.

 

^Thanks. Just bought one of those switches. Handy for when I go away for a few weeks. Might get a new battery too.

 

JagXV6, I know you are meaning well, but using that inside of a vehicle like ours is not the best idea. The reason why I state this is that the switch is only rated to handle 100 amps for a 12VDC system. The starter by itself is capable of pulling more than that. Also, with an alternator capable of outputting up to 150 amps (the rating of the one in our cars), it is conceivable if you use the alternator to recharge a battery that has been drained slightly due to needing to crank for a bit prior to the engine starting, you can get some fairly high currents going to the battery. I would just hate to see people have an issue with something like this. Something about BBQ'ed Kitty doesn't sound good. You need to make sure that the switch you get is rated for 200 amps or more. Sure, the switch is going to be a little bit bigger, but that will garantee no problems in the future.

 

A battery cut of switch isn't mounted in the car is goes under the hood. Rating is 100amps continuous, 1000A surge so it would be fine. Here is the one I was actually looking for http://www.batterymart.com/p-top-ter...ff-switch.html

A hassel anyway so for $80 I'd just fix the problem with a new battery.