Car battery disconnect or not?

[brightspark]

I know of a person who decided he could not be bothered to disconnect the battery and blow the ECU on a Jag..... £4200 later

dunno if im still here but if it was me id disconect battery .clamp the earth as near to job as possible not through door hinges engine that is rubber mounted or exhausts and becarefull with torch to not touch anything with it which would cause a short circuit

 

[Bsmith]

We were told to disconnect the battery negative on earth moving machines before welding on them in order to safe guard the alternator, although a fitter once told me that no harm would come to the alternator if the engine was left running and at idle speed. Wonder if there is any truth in either?

 

[Paul.]

I have spent many hours welding up fabrication jobs supported by gas and diesel forklifts, both with and without the engine running, and never damaged an alternator, it makes sense to remove an ECU though these things aint cheap.

 

[bugeyed]

bettery not disconnected

i had a friend weld a bumper on my truck...he forgot to disconnect the battery. It ran fine on the trip home, but the next day i was having some serious electrical issues. After putting in a new battery and alternator, plugs, and wires the truck still dies (slowly) when taken on a drive, then the battery needs to be charged up again... can anybody help me out?

If it is a chevy Colorado, I know they had a problem with the 2 little wires going into the back of the alternator. I had the same symptoms on my 2007 Colorado. It took weeks to figure out it was just those 2 little wires. It wasn't the battery or alternator, the shops!! had a grand old time changing out everything they could think of. The hole time it was a call back that Chevy kept to them selves. 2 wires $35 bucks. Welding might of hurt them wires.

 

[Richard.]

I disconnect it because it takes seconds to do it. But in all honesty I've never heard any horror stories when people haven't
Direct earthing is probably more important.
Like I say for what effort and time it takes to dis/reconnect it you may as well do it for good measure.

 

[dannyp]

i never disconnect the battery or alternator when mig welding. unlesss it's on equipment that has a big sticker specificly instructing me to do so.

IMO it's allabout eath placement with a mig

MMA needs a bit more care due to higher voltags,

Tig with H/F just dont go there allways wonderd what it would do to a car, untill i tryed it on a scrapper

 

[the snooper]

i never disconnect the battery or alternator when mig welding. unlesss it's on equipment that has a big sticker specificly instructing me to do so.

IMO it's allabout eath placement with a mig

MMA needs a bit more care due to higher voltags,

Tig with H/F just dont go there allways wonderd what it would do to a car, untill i tryed it on a scrapper

welded with mma on cars for years never disconnected any batteries, never had a problem

 

[doubleboost]

Disconnecting a battery on a modern vehicle can cause you loads of grief
I use a "surge protector" across the battery terminals
The same should be used when "jump" starting
Disconnect a battery on a new Renault at your peril
The only thing I weld now is the odd exhaust
As has already been stated you need a good earth

 

[cianh91]

depending on how much your doing i generally leave the engine running and you wont have a problem if its an exhaust tack it withengine running pop it off weld it no need to worry then

 

[the snooper]

depending on how much your doing i generally leave the engine running and you wont have a problem if its an exhaust tack it withengine running pop it off weld it no need to worry then

well that's a new one on me never heard of anyone leaving the engine running

 

[cianh91]

ye if you leave the engine running it stops the surge unless your using shocking high amps

 

[outofthefire]

I weld on brand new expensive wagons every day. At the last place I worked we used to use surge protectors but where I work now we always disconnect the battery. Personally I don't know what the best method is but i'd always do one or the other if it was my vehicle.

 

[Bill Edwards]

I weld on brand new expensive wagons every day. At the last place I worked we used to use surge protectors but where I work now we always disconnect the battery. Personally I don't know what the best method is but i'd always do one or the other if it was my vehicle.

I'm assuming that you never had any faults as a result of the welding using either method?

 

[Spark plug]

I have welded with both the battery on and disconnected. Never had a probloem or know anyone who has. Could all of scaremongering etc not have originated in the days of positive earth and dynamos?

 

[outofthefire]

I'm assuming that you never had any faults as a result of the welding using either method?

Someone once fried something (seem to think it was a starter motor) but I wouldn't be surprised if it was because he forgot the surge protector, it was bloody expensive though. Never had a problem at the place I work now.

 

[outofthefire]

At the old place we built a body on an electric 7.5 ton chassis, I can't remember exactly what we had to do but the procedure was a list of things that had to be disconnected or isolated before we could weld on it. Keeping the earth clamp as close to the point being welded was one of the points.

 

[daleyd]

Not a car as such, but I used to work on large industrial dryers that regularly needed welded repairs in their combustion chambers, some pretty major work lasting weeks in some cases.

Never disconnected anything, though the power was always off at the main isolator, and these had several plcs and quite a few inverter drives attached.

 

[Hitch]

Must be nice, welding under a car with the exhaust blowing all over you

 

[normspanners]

I have seen ecu's damaged by putting boost starters on to cars with totally flat batteries, as far as I can tell, the battery is basically not 'seen' until it has some charge. Boosters can go to 20v or more with nothing to hold them down, I dont like putting a boost charge on batteries until they have some voltage in them they then can work as a capacitor. afaik

 

[doubleboost]

depending on how much your doing i generally leave the engine running and you wont have a problem if its an exhaust tack it withengine running pop it off weld it no need to worry then[/QUOTE

I have seen ecu's damaged by putting boost starters on to cars with totally flat batteries, as far as I can tell, the battery is basically not 'seen' until it has some charge. Boosters can go to 20v or more with nothing to hold them down, I dont like putting a boost charge on batteries until they have some voltage in them they then can work as a capacitor. afaik

We always use a starter pack never a mains booster
You have to be so careful with modern stuff