Welding with Surge Protector?

Agree , although as a welder for many years / years ago we were always told to disconnect the battery ?
but some time ago I was convinced by someone that it wasn't necessary , so no longer disconnect the battery .

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Yes Nick, I have seen all sorts of problems caused by welders waving the electrode around everywhere, but confined to the weld site should create no problems.

About the battery..... there are a whole heap of circuits distributed in a vehicle, but they all connect to the battery eventually. Now that battery has a very low electrical impedance, less than one ohm. So if a rogue source of electrical energy greater than 12v somehow gets on to that wiring network it is going to be very smartly shunted to 'earth' (-ve) before it can do harm elsewhere. Disconnect the battery, at either positive or negative, and you have lost the benefit of that shunt. It is that simple.

Thanks Allan : not understanding electronics of the new motor cars I do get a little nervous when welding on my PX Ranger and for only peace of mind I do disconnect the battery , but for nothing else & and we were always told to put the earth right next to where we will welding which makes sense .
cheers

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AOR build campers and vans. What do they know about electrical engineering?
It is a common myth.
Ask them "why". It would be an interesting response.

They advise this as the circuit board in the gas heater is about $800 to replace and this can also affect other electrical components, eg, batteries, inverter, charger.

I would sooner be safe than sorry for the time it takes to disconnect the battery. Know idea if they are right or wrong.

I would suggest Shaker follow it up with AOR if he has concerns. It is also discussed on the Members Forum.

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So if you disconnect the battery, begin welding and the heater circuit board karks it, will AOR replace it free-of-charge? Suggest you get that in writing.

AOR tell you to remove the Truma PCB!

I too have given up disconnecting the vehicle battery and for that matter, the alternator as well when I have welding to do.
As suggested, I also place the earth clamp on the actual metal I'm about to weld, but I wonder sometimes what would happen if I arc off on this piece of metal and the other piece isn't touching the clamped piece? Would the circuit travel back to a suitable place where it will complete the circuit? (eg, the alternator?)
So, I have added a 12" lead with its own clamp, to my welder lead, so now I have two clamps which I place on each side of the weld. Paranoid? Maybe. But, touch wood, I've never had problems.
I must admit, I've never considered the battery acting as a shunt.

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Yes Gerry, there is always a possibility of the weld rod contacting a body part which is not in solid contact with the welder earth clamp. Weld current could then seek to return to the clamp via whatever path is available which can include negative wiring connections of a rating unable to carry the possible current with the result of fusing the wiring component. A long shot indeed, but possible.
Disconnection, or otherwise, of the battery would play no part in this scenario.

Your double-clamp scheme is a good idea.

I would prefer to discuss it privately, you can call me.

I'll go along with that. Using a Mig to weld exhausts in place we never disconnected any thing. Ground properly connected to the exhaust system and weld away.
From memory there was some theories around the time of changing from generators to alternators that diodes could be blown.

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RMD, maybe AOR had a Truma failure in a general period that welding had also been done and promptly blamed the welding. Pretty common behaviour when seeking a scapegoat. If a Truma can fail due to welding on the vehicle then the Truma has pretty poor electronics.

"Not storing batteries on concrete"? Is that rubbish still being perpetrated?

The 'cap removal whilst charging' thing has its roots way back when it was common practice to bench-charge batteries with a pretty constant current until the electrolyte boiled and then continue "giving it a good boil" for some further time. The battery tops were awash from acid spray. But it gave them a "good healthy charge". Really did happen.

Working in the electrical industry for 60 years you get to see it all. And to those who doubt my acumen........ you do learn a thing or two.

If it *is* an issue, wouldn't just pulling the 12v fuse and pulling the 240v plug (if fitted) be sufficient to isolate the heater?

Hey, Allan and RMD,
The battery thing is one of the other myths I was thinking of.
Cold , decreases a batteries performance, but doesn’t damage it. Same battery that wouldn’t start the car on a frosty morning probably would when the day warms up.
Heat is part of what kills batteries. Over the years , have seen batteries moved from hot locations (under bonnet) to under tray in a Ute case , and then the battery was performing for years as it should. We had a ford tractor, the battery was on top of the engine under the bonnet, one year per battery, then we moved it out and got years out of them.
Even had one Harley owner claim , a piece of rubber under the side stand on his bike keep his battery from going flat.
But I guess this myth will be with us forever!
Cheers
Shane

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Hi Jarse,

Now, before someone asks, I have not sat down with a Truma heater and a welder and performed experiments!!! And I don't need to.

Pulling the Truma 12v fuse does not achieve "isolation". There is still wiring attached to the Truma input. Just don't stick your welding rod on it. In point of fact, this wiring is waving around in the breeze like an antenna and could conceivably pick up an electrical charge if sufficient of such was present, but rather unlikely.
If that wiring was still connected to the battery then the battery acts as a pretty good shunt against voltages over 12v. Typical power supply inputs to electronic devices include capacitors that also provide shunt paths for unwanted induced voltages to protect the electronic components further within the circuit.

Isolation alone does not always provide maximum protection against unwanted electrical intrusion. It is common to isolate then "earth" the circuit.

Re the "not storing batteries on concrete" - a very sensible move in the day when batteries had wooden separators and battery cases were made from hard rubber that was slightly porous.

Storing these batteries on concrete was a no-no, as the porosity of the hard rubber case led to slow discharge.

Fast forward to the late 1960's and early 1970's, and battery cases are now being made from polypropylene - as they still are today.
As a result, the belief that batteries self-discharge on concrete, is no longer a valid issue, as it was, when battery cases were made from hard rubber.

In fact, there is at least one good reason to store your batteries on concrete, particularly if you reside in a high temperature region.
Because heat is the killer of batteries, storing batteries on cool concrete will more than likely improve their lifespan - provided you keep them charged, of course.

If you live and work in a hot climate, your battery has only 2/3rds the lifespan of a battery being used in a cold climate - so anything you can do to reduce your battery temperature will have a life-lengthening effect on it.

Cheers, Ron.

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Ron,
The batteries of the 1950's indeed had cases composed of a rubber compound. it was somewhat fragile to impact but served well to contain the acid without reaction or degradation. They certainly were not "slightly porous" as you suggest. If so then the supporting steel trays in vehicles would soon corrode. Corrosion around a battery in a vehicle was more likely due to overcharging with accompanying acid boil-out.
If acid were to leak onto a concrete floor it would be obvious due to the chemical reaction and would etch the concrete.. It would not lead to cell discharge unless there were corresponding leakage in more than one cell to complete a current path.

How do I know all this? Well, in the 1950's I was the Range Electrician of Range 'E' at Woomera. I had two electrical assistants caring for about 350 lead acid batteries which were used in firing circuits, camera drive supplies etc. It was quite a business charging these batteries and carting them around to places of use and I got to learn quite a bit about those batteries. In the charging shed they were stored on the concrete floor then arrayed on timber tiers for convenience but in the places of use they invariably sat on the concrete floor. At no time did I experience discharge of unconnected batteries whilst sitting on concrete or any sign of case porosity. One or two cracks, yes.

However the origins of the myth may lie in even earlier lead-acid battery construction in which rather fragile rubber 'cell-jars' were contained within wooden crates. If these crates were subjected to moisture on their bottoms then unequal expansion would occur to distort and weaken the wooden crate. The concrete floors of the time were not particularly waterproof and easily contributed the offending moisture. Thus may lie the dictum of not placing these batteries on a concrete floor or even an earthen one.

Allan,
The way I see it is, if the battery is disconnected, the battery is then removed from being able to quench anything and any induced voltages high enough to affect CMOS/MOSFET devices is more likely to and able to easily present itself to the sensitive device without being nullified in any way.

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RMD,
Yes, I agree absolutely. It is obvious to anyone with electrical training and experience.
How these myths get started is beyond me but they do and are readily accepted.