Precautions when battery changing. - gordonbennet
Don't need to worry about my old MB, it doesn't seem to bother at all when the battery is disconnected...which with it's previous ECU/wiring loom problems was quite a few times..;)

But i hear that some cars do have problems if battery power is lost, and more problems if you mess up connecting a new battery, yes even if connected correctly.

It'll come to pass probably this winter that the BMW compact battery will die, i shall use my trusty jump pack to maintain constant power to the car whilst performing said renewal..i understand BM's can be temperamental if power is lost for some time.

Do others take similar precautions, or just disconnect/reconnect anyoldhow?
Precautions when battery changing. - ifithelps
Slight drift, but you need to avoid any sparks when changing the battery itself.

I've seen one explode and it could do a nasty injury - the top rips off and there's acid and bits of lead everywhere.

Turn everything off before connecting/reconnecting the charger and never lean over the battery, particularly with your face.

I always turned off the charger and left the battery for a good few minutes before transporting it.

Precautions when battery changing. - gordonbennet
I've seen one explode and it could do a nasty injury -

Yes, seen that too, when a rather daft driver shorted a freshly charged truck battery by dropping a spanner between the terminals...flash boom and my jeans dissolved, lucky he wasn't blinded only his very thick glasses saved him, extremely nasty.
Precautions when battery changing. - Another John H
>>..flash boom and my jeans dissolved

it's a long time since I've been to a party like that..

I'll get me coat.
Precautions when battery changing. - gmac
If I am doing anything electrical on a car these days I read the manual first or contact the dealership to find out if there are any set procedures.

The car I currently run requires the battery be disconnected for ten minutes prior to touching anything to allow the onboard systems to shutdown. Failure to do this can and usually does result in some messages in the driver information module and an expensive £50 reset at the main dealers.
Precautions when battery changing. - Old Navy
I have been very careful with batteries ever since I saw a dropped tool weld itself across the terminals of an installed submarine battery cell, (900ah per cell). Fortunately the battery had not been gassing recently and was well ventilated or I would not be writing this.
Precautions when battery changing. - Roly93
In the hangar I used to work in, there was a large H&S poster with a picture of an aircraft battery with the top blown right off, demonstrating the effects of a hydrogen explosion after charging without proper ventilation.
Precautions when battery changing. - David Horn
Do not assume that 12V can't hurt and try to pick the battery up by the terminals. Don't ask...
Precautions when battery changing. - doctorchris
When I was at school in the mid 70s, we used 12V car batteries as power sources for some of our physics practicals.
There was nothing more fun than shorting the battery terminals and watching the sparks fly.
By the way, we didn't wear goggles, decontamination suits, etc. Just school blazers and ties.
Precautions when battery changing. - Mick Snutz
If anteaters could drive, would they place their tongues on the terminals to test it like we humans test 9v batteries?

I'll get me coat too.
Precautions when battery changing. - bell boy
i always treat batteries with great respect
if i have to charge them i always begin on trickle charge before i put the guage on
"it wont take anymore captain" overboost charge or your off to china mate

batteries are mainly sealed for life now so you really should only trickle them anyway
Precautions when battery changing. - Dynamic Dave
Back when I was a teenager I had a CB in the bedroom powered by a car battery. Used to charge it up weekly and took great delight in holding the charger crocodile clips just above the open battery tops and rubbing them together to create a spark to ignite the hydrogen gas given off. Oops! I guess I was lucky not to have blown myself up.
Precautions when battery changing. - ifithelps
Holding a match to an aerosol burst of hairspray is a good idea if you like a spectacular flare and want to go through the rest of your life with one hand.

Most of the battery horror stories relate to fast charging - 'boiling' the acid.

A trickle in a well-ventilated area should be safe enough.

Precautions when battery changing. - Bill Payer
It'll come to pass probably this winter that the BMW compact battery will die i
shall use my trusty jump pack to maintain constant power to the car whilst performing
said renewal..i understand BM's can be temperamental if power is lost for some time.

Don't know about BMW but sometimes dealers can be pretty competitive for stuff like this, and they may change it for you. So if there are any snags then it's down to them.
Precautions when battery changing. - Bagpuss
My BMW used to confuse the garages with an error buffer full of "Low Battery Voltage" errors. This was because I used to leave it standing for 3 - 4 months at a time. No other problems.

The battery in my Merc W124 died last winter. It had a build date of April 2000 so not really surprising. I jump started it, drove to the dealer, whipped the old one out and put a new one in. Took about 10 minutes. However I'd forgotten how heavy a 100Ah lead acid battery is, my poor back, guess I'm getting old...
Precautions when battery changing. - lotusexige
Once upon a time I was changeing a heater plug in a Land Rover. I smelled something burning and noticed a bit of smoke. A couple of seconds later I realised that the smell and smoke were from my wrist. I had rested my left hand so that the bracelet of my watch shorted from the live of the battery to whatever else it touched. I still have the scar 25 years later. Needless to say it made me a lot more carefull about disconnecting the earth before delving into the nuts and bolts and I have not worn a watch with a metal bracelet since.
Precautions when battery changing. - bell boy
its one of the reasons i dont wear jewelry or ties
Precautions when battery changing. - ifithelps
...the bracelet of my watch shorted from the live of the battery...

Friend of mine did the same thing while mounting a dry Varley racing battery in an aluminium box.

Never seen someone try to remove a watch so quickly.

Several of the links on the bracelet of his Rolex were welded together.

Edited by ifithelps on 23/06/2009 at 17:03

Precautions when battery changing. - gordonbennet
We are a relatively lucky lot to still be knocking about by the sounds of it.;)

From the replies it seems few are bothered about maintaining power to the vehicle whilst a battery change is effected.

That surprises me, or maybe i'm a little paranoid about possible problems.

My sons former neighbour's changed the battery on a 3 series one weekend and the car put the ABS (or was it Traction Control?) light on after that....he ended up going to BMW to reset the thing, something along the lines of turning the steering lock to lock in a certain sequence and other such things for the car to 'learn' the straight ahead position (not sure exactly but it was something like that)

I shall continue to maintain power supply if i change any battery, knowing my luck it will be the world's most expensive ECU that fries.