TIG welding and the CANBUS electrics

[Tomcat]

Can anyone give advice/reassurance about TIG welding a bracket on the frame? I'm a bit concerned that the CANBUS or ECU will somehow get fried. I'll disconnect the battery of course, but does anyone have any other recommendations (based on practical experience please )?

Thanks
TC

 

[Myke Rocks]

Welding on bike

This has all been done before, But:
First of all Cansbus systems are very robust, and not susceptible to transient damage.
No, when welding on a bike, the critical area is the earth path.
If you just clamp the earth onto the bike, anywhere, you may generate problems, from electrical component failure to bearing failure.
If you are, for example, welding handlebars, put the earth directly onto the handlebars, not the frame or headstock. Similarly, if welding frame, be sure to earth onto frame, with earth ideally close to weld. After that welding is straightforward.
Some people suggest disconnecting battery, but I have never been able to usderstand why this should be an advantage, since it leaves the electrical system free to "float" with the possibility of high induced voltages, whereas when the battery is kept connected, voltages are limited to 12v.
Myke

 

[Fanum]

Some people suggest disconnecting battery, but I have never been able to usderstand why this should be an advantage, since it leaves the electrical system free to "float" with the possibility of high induced voltages, whereas when the battery is kept connected, voltages are limited to 12v.
Myke

I'm no electrician, but shirley if you put stupid high voltages into a circuit, it's going to go around that circuit at that voltage.....why would the battery limit it to 12v?

The idea of disconnecting it is to break the circuit so it can't flow around and fry things

Here we go........LINKY (from Repair of vehicle bodies
By Alan Robinson, Andrew Livesey)

 

[Myke Rocks]

I'm no electrician, but shirley if you put stupid high voltages into a circuit, it's going to go around that circuit at that voltage.....why would the battery limit it to 12v?

The idea of disconnecting it is to break the circuit so it can't flow around and fry things

Here we go........LINKY (from Repair of vehicle bodies
By Alan Robinson, Andrew Livesey)

Keeping the battery connected limits the voltage which may be in the circuit to the battery's 12v. It acts as a capacitor, limiting any surge which may occur in the circuit.

When you disconnect the battery, any induced voltage in the 12v + cables, which may occur as a result of the welding process, has no limiting factor, & the resulting surge is much more likely to cause damage than that which would occur if battery meains connected.

Unfortunately, disconnecting the battery has become a standard practice because of the original Joseph Lucas alternators as originally fitted to cars. These units were so bad that if one connected a battery charger to the vehicle with the alternator connected, the alternator failed. Similarly a bad connection on the battery "blew" the alternator. Situation was so bad that it became industry practice to disconnect the battery before doing anything to the vehicles.
Myke.

 

[Phil Clarke]

I did quite a bit of welding on my 05 GS - several re jigs of pannier frames and a home made rear rack. I disconnected the battery completely (only after reading long way round...) and kept the earth clamp as close to the weld area as possible and had no bother at all.

 

[Tomcat]

Thanks for the feedback - sounds as though there is no need to worry

 

[Fanum]

Keeping the battery connected limits the voltage which may be in the circuit to the battery's 12v. It acts as a capacitor, limiting any surge which may occur in the circuit.

When you disconnect the battery, any induced voltage in the 12v + cables, which may occur as a result of the welding process, has no limiting factor, & the resulting surge is much more likely to cause damage than that which would occur if battery meains connected.

Unfortunately, disconnecting the battery has become a standard practice because of the original Joseph Lucas alternators as originally fitted to cars. These units were so bad that if one connected a battery charger to the vehicle with the alternator connected, the alternator failed. Similarly a bad connection on the battery "blew" the alternator. Situation was so bad that it became industry practice to disconnect the battery before doing anything to the vehicles.
Myke.

No disrespect Myke, but that feels totally wrong to me, very counter-intuitive.....but as I said, I'm not an electrician....

When I Googled this a bit earlier and found that extract I linked to, there were literally hundreds of references to completely disconnecting the battery before TIG welding

 

[Myke Rocks]

welding on bike

Yes: it does sound counter intuitive to anyone who is not into the theory, but, believe me, it is correct.
Most of the people who reccomend disconnecting battery are, as I said earler, led by the fact that "everyone does this", without regard to the origins of the practice, which I have already given.
I write with reasonable knowledge on the subject in that I am an electrical engineer with a lifetime of eperience of electrical "noise" induced problems.
(Electrical noise is the current or voltage induced from one conducter to another even though they do not actually touch)
Such "noise" is often the cause of electronic failures. An extreme example is lightning. A direct lightning strike on an electrical installation will blow it to bits.
A strike nearby will generate noise in the lines, which destroys phones and fax machines. (I live in a country area, and have lost many phones & one fax machine because of it.)
Myke

 

[Schtum]

Will a bike battery have sufficient capacitance to smooth out any spikes? I remember having an exhaust back box on a car electric arc welded a few years ago and the garage attached a BIG auxiliary capacitor across the poles of the battery.

 

[Myke Rocks]

welding on bike

Will a bike battery have sufficient capacitance to smooth out any spikes? I remember having an exhaust back box on a car electric arc welded a few years ago and the garage attached a BIG auxiliary capacitor across the poles of the battery.

Should have, but better than disconnected in my eyes.
Though, regardless, The earth path is the most critical item.
If earth path is correct, then the conection or otherwise of the battery should be irrelevant.
Myke

 

[Fanum]

If the clamps were poorly placed, what happens to a 12v 19ah battery if it gets 200 amps/240v dumped through it?

it's gonna make a mess isn't it ?

 

[Myke Rocks]

If the clamps were poorly placed, what happens to a 12v 19ah battery if it gets 200 amps/240v dumped through it?

it's gonna make a mess isn't it ?

I cannot think of any circumstances which could lead to the circumstances you describe, except putting the welder earth onto the +ve of the battery. Now that would be foolish.
Myke

 

[Fanum]

I cannot think of any circumstances which could lead to the circumstances you describe, except putting the welder earth onto the +ve of the battery. Now that would be foolish.
Myke

Indeed.

What if someone followed what some guides say and just disconnected the positive terminal of the battery, leaving it close(ish) to the frame?

Isn't there a chance there could be some arcing across through the frame?

 

[Myke Rocks]

Indeed.

What if someone followed what some guides say and just disconnected the positive terminal of the battery, leaving it close(ish) to the frame?

Isn't there a chance there could be some arcing across through the frame?

Would not matter, in fact, bolting +ve to to the frame would also reduce the possiblilty of an induced voltage in it, since the entire electrical system would then be at a common voltage, but I would lose my nerve at doing this, in case some of the +ve cables became an earth path for the welder. (The consequence of this would be - Burn the bike & claim off the insurance!)

 

[(RIP) Bin Ridin]

I think a proper return path is the critical bit. You will all have seen a welder starting, not happy with arc, and then wiggles or wire brushes the earth clamp. better to make a good connection before starting.

Would avoid electric welding on a bike if possible and would consider the possibility of cracking at the weld due to the local heat involved. Can the bracket be made as a clamp ?

 

[R1200GSA]

Keeping the battery in place and using a surge protector over the battery, seems to be standard practice for the bodyshops these days anyway.

 

[mechcanico lee]

I work in a car body shop and dissconnecting batterys can cause more problems than its worth, lost radio codes , windows, sunroofs, alarms ,drive parameters, and adaptive learn stuff losing there programs.
In thousands of body work weld up jobs NEVER have i come across any fried/blown ecm/ecus and cars have lots of different ecms, this is said just from hands on experience , like someone said in the post use a surge protector across the battery, but saying that maybe cars are better protected against voltage surge..............i dont know

 

[Fanum]

I work in a car body shop and dissconnecting batterys can cause more problems than its worth, lost radio codes , windows, sunroofs, alarms ,drive parameters, and adaptive learn stuff losing there programs.
In thousands of body work weld up jobs NEVER have i come across any fried/blown ecm/ecus and cars have lots of different ecms, this is said just from hands on experience , like someone said in the post use a surge protector across the battery, but saying that maybe cars are better protected against voltage surge..............i dont know

The problem I have with the issue (and hence why I asked the questions in this thread) is that I sometimes get into a position where I'm asking a back-street welding shop type place in Morocco to do an emergency repair weld to a bike so I can get a customer back on the road.

Nearly everyone has heard, rightly or wrongly (and mostly down to E&C on the LWR) about disconnecting the battery so I'm standing there with a broken bike and an customer hoping we can keep him/her on the road, looking to me or one of the Moto Morocco team to get the welder to take appropriate precautions.

The experience of the guys here says one thing, a Google search and numerous books/articles on TIG welding says another

Difficult

 

[RickG]

A 12v battery will certainly do it's best to clamp down higher voltages but surely only if the transient is applied across it? If you are welding and the battery is connected but the electrics are switched off (hence positive supply not connected to the battery) then the earth (negative) is common to both welder and electronics, but any voltage induced in the circuits by the welding can surely rise to a higher voltage as it's not tied to the 12v line ?

I'm no electrican either so don't claim to know what I'm talking about.

I'm sure there is already good protection on the can-bus and ECU as there simply darn well needs to be in an automotive application but I'd certainly do as the others have suggested regarding earth clamping near the site of the welding.

Doesn't the plug to the ECU come off realatively easily? Wouldn't that be a good move in terms of isolating the electronics while you weld?

 

[Tomcat]

OK, to go back to my original question - I now have a bit of practical experience as the weld has been done (TIG and MIG). The welder clamped the earth very close to the weld site, and disconnected the battery earth. BTW, the weld was to fix a hairline crack in the bracket holding the rear of the gearbox casing to the frame.

Weld completed, everything reconnected and all is well . I did take note of Myke's comments, but if the guy doing the welding wants to disconnect the battery earth I didn't feel I had enough knowledge to disagree.

Thanks to those who posted advice - it was reassuring the learn that CANBUS is robust technology. Even so, I had to walk outside for a calming smoke whilst the welding was done . I'm off for some fun in the Ardennes and then the Alps in a couple of days so if it had all gone pear-shaped and fried the ECU it would have been a total bummer.