StuRox

StuRox

Well-Known Member
Just going to weld up my sill tonight - question is - do I just need to disconnect the negative from both batteries, or do I need to disconnect the live's too?? Also, do I need to leave the car for a bit to 'die' after disconnecting the batteries before starting?

Thanks in anticipation
 
I've always disconnected both leads just in case, I've heard something about frying alternators by not disconnecting something...not sure how true it is
 
Well, suppose since I am disconnecting the neagtives, going to lose power and memory to electric stuff anyways, so might as disconnect them both.

Just wasn't sure if I needed to leave it without power for a certain length of time....so will disconnect before I eat my tea just to be safe
 
StuRox said:
Just going to weld up my sill tonight - question is - do I just need to disconnect the negative from both batteries, or do I need to disconnect the live's too?? Also, do I need to leave the car for a bit to 'die' after disconnecting the batteries before starting?

Thanks in anticipation
Click to expand...


I would be removing both batteries, disconnecting the alternator and as it's an auto it probably is an EDC car, so locate and disconnect the engine ECU.

Dave
 
ive never disconnected a battery, but ive never welded on a car with computers on it....

on older cars just make sure the earth clamp is securely on good clean metal fairly close to where youre welding and you wont fry anything.

dont forget to have a bucket of water handy to chuck on the flames.
 
I have done welding on many a car and commercial vehicle over the past 30 years and never disconnect the battery and that was when doing it for a living.


Did quite a bit of welding on my 300 Tdi ES for the last Mot and all was ok, I always place the earth clamp as close as possible to where I am welding and I make sure itÂ’s a good earth.
 
Well, have been welding through the evening, more I poked about the more I had to make up and weld...still not finished....hopefully will get done tomorrow evening.

All I disconnected was both batteries - both positive and negatives. Didn't do anything with the alternator or ECU, so will see what happens when i re connect the batteries...hopefully the old girl will spark into life.....
 
Well, connected a battery up this morning, and she sparked into life - no problems with alternator - as volts were good, and guess none with the ECU given she started.....only moved her to put her on some ramps to give me better access tonight when I finish up the welding.
 
I have always disconnected battery (-ies) when electric welding vehicles , meant to do the alt on my first EDC when replacing the floor but forgot and was all fine so havnt bothered about it since . I always get the earth as close as possible and use magnets if necessary mainly as it improves the welding condition (with my welding at least) .

Saying that , I may just have been lucky up til now .....I have to put a wheel arch on Link this weekend and now I am worrying about the alt and EDC again ....
 
Maybe there should be a 'Mythbuster' thread?

Has anyone actually had a problem when welding without disconnecting their battery?
 
Well with everything being said, hooked up batteries again and went for a spin tonight, and everything seems good...so hopefully everything is
 
ricc said:
dont forget to have a bucket of water handy to chuck on the flames.
Click to expand...

Well, found this out last night as when I was underneath welding the inner part of the sill, thought to myself, its a bit warm.....then realised my top was on fire :eek:
 
I personally have never disconnected batteries when welding and I dont know of anyone who does, never heard of any issues regarding this, in my mind its a total myth, at the end of the day electricity follows the path of least resistence i.e. it goes straight down the earth cable, you can hold the bodywork, you could even lick it and there would be no shock heading your way...
 
Jongould said:
I personally have never disconnected batteries when welding and I dont know of anyone who does, never heard of any issues regarding this, in my mind its a total myth, at the end of the day electricity follows the path of least resistence i.e. it goes straight down the earth cable, you can hold the bodywork, you could even lick it and there would be no shock heading your way...
Click to expand...

ive had problems with the radio after welding work done on car and erm i wouldn't lick the body work on my 110 as a chap goes past with his mutt every morning and it ****es on me car every time.. dirty fecker
 
biscuits said:
ive had problems with the radio after welding work done on car and erm i wouldn't lick the body work on my 110 as a chap goes past with his mutt every morning and it ****es on me car every time.. dirty fecker
Click to expand...

Fancy letting his mutt watch him as he ****es on your car....wonder if he is trying to train it....
 
biscuits said:
ive had problems with the radio after welding work done on car and erm i wouldn't lick the body work on my 110 as a chap goes past with his mutt every morning and it ****es on me car every time.. dirty fecker
Click to expand...


Very doubtful it was the welding that caused this, take a look for 'faraday cage' on google, this will explain what im on about, there is no logical reason for any sort of electrical charge to deviate off course and affect other items, its a case of simple physics im afraid.

There is always the possibilty that if the welder removed the battery and refitted it he could have spiked the radio but I can't imagine this happening. Prehaps it was coincidence that it failed at the same time, sometimes **** happens like this....
 
The problem with it, as I understand it, is when you are actually striking the arc (especially in the case of arc welding, and even more so with HF start TIG). The arc being struck causes explosions of current to radiate out before it 'finds' the earth and starts flowing. The alternator has little diodes in the rectifier pack that can be blown.

my series 3 has a plate that states 'disconnect battery and alternator before arc welding'. It takes about 10 seconds. I don't see any good reason not to do it!

I have heard of people knackering sensitive components whilst welding. I heard of someone blowing up a battery as well, and showering themselves with acid, whilst they were welding! I'll never risk it anyway.
 
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