Is anyone using an arc welder with an offgrid system

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Re: Is anyone using an arc welder with an offgrid system

Post by hary » Sun, 21 Jul 2019, 20:28

I just plugged in mine to check if it works and it went BANG !

There was some small arc welding noise inside, then bad electronic burned smell.

It ran for 5-15 second at most.

I had only time to read the voltage (26.1V) on the nice coloured screen, and output power (0.0W, normal as there was no load on it), then I switched it OFF despite fans and screen were still running, to avoid more problem or any fire !

I'm so disappointed ! I just wrote a report to the seller. I hope there won't be to many problem to get another one or get this one fixed !

Very bad day for me !

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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Mon, 22 Jul 2019, 05:36

Oh no, that is terrible.

Perhaps something became loose in the transportation?

Mine continues to work well. My voltage is also 26.1 when the batteries are fully charged and 23.7 at lowest.

Recently I have been leaving it turned on and just using the 200A contactor to turn it on and off.

By the way, when you first connect the batteries, it is worth using a resistor (=24V lamp) in series until the internal capacitors charge up to avoid a big spark when attaching the terminals. But you presumably were past that and turned the inverter on with its switch.

I hope that things improve for you.

Best Regards,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by hary » Mon, 22 Jul 2019, 12:13

The seller responded immediately and ask to check inside.

I opened the case and found this :
IMG_2378.JPG
IMG_2378.JPG (1010.14 KiB) Viewed 797 times
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I knew about charging the capacitor, so I used a bulb like you said and waited for the voltage against the bulb to fall near 0V, then pugged the inverter to the battery.

By the way, do you have any safety protection like fuses inline wit the inverter ?

Checking inside mine showed there are no fuses ! What would happen in case of short circuit somewhere in the inverter ? I'm quite afraid of these big Amp, A.h and big battery bank getting shorted !

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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Mon, 22 Jul 2019, 13:47

I did have a 200A circuit breaker but the terminals are too small for 200+ amps and it got too hot so I have temporarily removed it. My charger/BMS does disconnect the contactor if an abnormal current flows. It is quicker than a fuse. Your inverter is 20% bigger than mine, so I guess it could draw 265amps (mine goes to about 220A max continuously).
I agree it is good to be scared of huge amperages. My AVASS cells can probably deliver over 3,000amps for a short while.

I wonder where Q30 is from your unit?

Those are good quality FETs and from memory there are a lot of them in parallel but it looks like that one has ruptured with huge current flowing.

Is that the only visible sign of damage?

Regards,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by Richo » Tue, 23 Jul 2019, 12:59

Mmmm I've seen plenty of popped fets over the years.
What is unusual is the broken left leg.
If this is the gate then that is floating.
Floating gates are bad.
They have a tendency to turn on when you don't want to.

I'd say the leg was stressed from bending to fit into the PCB.
The heatsink moved during manufacture or shipping causing it to snap.
Unit was turned on with a floating gate.
Pop - there it goes.
So the short answer is NO but the long answer is YES.
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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Tue, 23 Jul 2019, 13:46

Hi Richo,
Yes, I would say you are correct.
That would explain pretty much everything. First time run of the inverter, shipped from China to France, bad lead bend in the factory, that FET turning on by slow charge build up on the gate of the order of 15 seconds fitting the failure description.

I once had a similar situation in a charger I built where the lead on a dense SMD three phase driver chip to a gate was not properly soldered when I heated it. Fortunately I tested with a current limited power supply but was puzzled initially when the short materialised after about 20 seconds.

If this OC gate was the cause, it is unlikely there would be other damage with the current in the other part of the bridge distributed among all those FETs. As long as the trace on the PCB was not damaged.

My 5KW almost identical unit has been running perfectly so I do not believe this is a design problem or a result of overall shoddiness. I inspected the interior of mine before turning on. However I doubt I would have noticed a break in a gate lead.

Cheers,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by coulomb » Tue, 23 Jul 2019, 14:10

Richo wrote:
Tue, 23 Jul 2019, 12:59
What is unusual is the broken left leg.
Ooh! Well spotted! :geek:
If this is the gate then that is floating.
Well, it's on the left where all gates seem to be, and it goes into a PCB hole marked with a capital "G". I'd say it's the gate :)

I agree; a floating gate is a Bad Thing™. With luck, the single FET could be replaced, and no need to do the warranty thing (it always seems to be hard to get electronic gear back *into* China for repair).
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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Tue, 23 Jul 2019, 14:28

Q24 also looks like there might have the start of a crack in its gate lead. Certainly a crease in the metal.

Cheers,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by hary » Tue, 23 Jul 2019, 19:07

Hi all and thanks very much for your observations and valuable informations.

The seller offer to send a new power board if I feel able to replace it on my own.

I think I'm ok with the replacement. Should I be aware of any difficulties to replace it ?

@doggy Dave, Yes it seems to be the only damage, but I'll have another and closer look.

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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Tue, 23 Jul 2019, 19:44

Hi Harold,
I think that is a good offer.
When you finally start it again, see if you can borrow a regulated power supply with current limiting. Set for 24volts and 3amps then connect.
If this is not possible, you could so what I did when I first ran mine. I put a couple of small 12V VRLA batteries in series for 24volts. They could still deliver 10-20 amps but a lot less than a Lithium bank. You could put a 5A fuse in as well. Then run it with no load.
Cheers,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by hary » Wed, 24 Jul 2019, 01:46

@doggy , So I'll tell the seller I'm ok to replace the board when receiving the new one.

I have only a small RUI DENG DP5005 power supply with constant current. I would be a little afraid to power a such big inverter with a so small device.

One more observation I could say is :
The inverter seemed to work fine after the "small arc welding noise" it made, for the short time it took me to reach the switch and turn it OFF.
Is it possible that after the Q29 IRFB3206 MOSFET blew up, it was not conductive any more at all and so the inverter was able to work fine on 6 FETs instead of 7, Q29 being fully open and not causing any more damage ?

That would maybe also confirm your observation/thought.

I'm wondering to take that Q29 apart and try to start the inverter again. So, at least, I could run my small 100W fridge. It's so hot here now !
.

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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Wed, 24 Jul 2019, 03:49

Hi Harold,
Yes, it is very possible that now that FET is blown it will work on the other FETs. Get a multimeter and check that there is not low resistance between the Drain (centre) and Source (right) legs. There was probably sufficient energy to open circuit the FET. However, most of the FETs I blow up end being a dead short circuit. So make sure first that it is not shorted or you will make more problems. The inverter only draws a few amps under no load which is why I suggest using a power supply or small batteries with fuse to test. precharge the internal capacitors first as you did with the light bulb otherwise you would blow a fuse.
Cheers,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by hary » Wed, 24 Jul 2019, 04:30

@doggy I was too impatient to try with the constant current power supply, so, not waiting for your last message and advice, I slowly charge the capacitors, then adjust the voltage to 26V, constant current to 3A and turned it ON and ....
it worked !

I then adjusted the power supply to its max current, 5A and tried some small devices (filament light bulb, a 100W soup mixer).

I could also go and check the different menu and adjustment available on the inverter's control panel.
The NoLoad consumption is 32W as advertised by the seller, so I guess no other load is happening now.
So it seems to work normally now that the FET is fully OPEN.

I might plug it in back with the big cable tomorrow and have a try with the 100W fridge.

I still need to think about a safety device in the circuit. That inverter has absolutely no in line fuses inside !

You're all part of a genius team, indeed.

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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Wed, 24 Jul 2019, 09:33

Hi Harold,
Glad it worked okay.
You would have no trouble with a 100W fridge- though there will be a surge when it turns on but nothing problematic.

It is excellent news the seller is replacing the power module.

With a replacement FET the other one can probably be easily fixed.

Regards,
Dave

PS- I know the French Canicules very well. I can remember 16 days in a row over 36deg in the Loire Valley! One day we visited the Nuclear Reactor just to get some cool air (I am NOT a nuclear energy enthusiast even though my degree is in Theoretical and Nuclear Physics- but they are usually cool inside).

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Re: Is anyone using an arc welder with an offgrid system

Post by Richo » Wed, 24 Jul 2019, 12:28

Yes with parallel fets you end up with cascade failure.
With such a light load it should be ok for a while.
So the short answer is NO but the long answer is YES.
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Re: Is anyone using an arc welder with an offgrid system

Post by hary » Wed, 24 Jul 2019, 13:29

@Richo Well this big 6000W inverter is mostly for power tools, so I guess with only a small 100W motor, even with big inrush current, it should be able to start and run the fridge.

And as the failure was due to this broken GATE leg, there should be no cascade failure with such a small load.

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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Wed, 24 Jul 2019, 14:03

Hi Harold,
I totally agree. With only 1 of 7 FETs dead (and open circuit) in half the bridge, you could probably (in theory) run it up to 6*6kW/7 or about 5kW. But I would not do that if I were you.
I would have no hesitation in running a 100W fridge or even drills and lights.
I can think of no reason for any of the other FETs to fail.
Hopefully your new Power Module comes quickly (after the French Tax Man gets his chunk).
You should be able to get someone to replace the damaged MOSFET for you thus giving a whole spare module.
So, with any sort of luck, you will be a winner after all.
I have bought many electronics parts, while in France, from Farnell. Some parts come from England and some from the Netherlands when you order from the French site. Parts usually come in 24hrs (I realise you do not need quick delivery). I had a look and they have a close partner called AVNET and AVNET stocks those FETs. Probably worth ordering one or two before Brexit makes it harder and more expensive.
Again, if it was my inverter, I would do what you are doing but I would not replace, remove or otherwise touch your damaged power module until after your replacement arrives, is fitted and working.
Best Regards,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by hary » Wed, 24 Jul 2019, 19:05

Hi Dave.

I found some cheap IRFB3206 on Ebay :
https://www.ebay.fr/itm/5PCS-IRFB3206PB ... SwbdpWZuDN

I have no idea if I can trust or avoid those cheap ones and prefer buying some from a proper seler like Farnell, Mouser, or Digikey.

I'll try to run the fridge this evening.

PS : The LOIRE Valey is where I'm from (Chateaudun near Chartres). I'm now inthe south of France (Perpignan).
Fortunately, we're not so hot at that moment.

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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Wed, 24 Jul 2019, 19:16

Hi Harold,
They would almost certainly be good. Probably exactly the same as in our inverters. However the French Tax man might charge you extra.
Ones from Mouser, Digitech or Farnell would be totally genuine.

I'll be back to France for just a month next year in Bretagne. My daughter and two grandsons live in Guernsey and we will holiday together.

We miss the 5-6 months of each year we used to spend in France. But I do have another daughter there at the moment (around Bordeaux)- she goes each year for a couple of months.

We had so many favourite places. However the Loire area was always special.

Best Regards,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by hary » Thu, 25 Jul 2019, 04:18

Hi Dave.

I connected the inverter with its big cable and plugged in the fridge.
It's been working all the evening. I'm going to stop it for the night for safety and also because I don't have LOW VOLTAGE disconnect devices working by now to protect my LiFeYPO4.

Still waiting for the seller to confirm he will send the new replacement power board.

If you're coming to France next year, you could maybe visit us at our off grid straw bale house in Ceret, close to Perpignan.
That's a very small and simple house, but we would be happy to make you our guest.

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Re: Is anyone using an arc welder with an offgrid system

Post by hary » Fri, 16 Aug 2019, 21:36

Hi

I finally received the new power PCB board from the seller.
I installed it and the inverter works ok.

Now , I need to install it with big 250A wire and test it with big power tools and see if it's ok.

I also received the communication and remote control kit with a specific software. By now, I can't figure out how to install the software. It seems it only install on old XP98, 2000, 2003, NT windows !

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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Sat, 17 Aug 2019, 10:32

Hi Harold,
I am very pleased they sent you the new module and that you were able to install it and it WORKS! That is good customer service and you should be able to make a spare power module that you probably will never need.
I used 75mm2 wire and also a hydraulic crimping tool.
I also used conductive paste on all the battery, shunt and other high amperage connections.
I kept the critical cables as short as possible.
Things get slightly warm at 230amps, but quite good really.
Cheers,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by BaronVonChickenPants » Tue, 24 Sep 2019, 12:16

Hi Doggy,
I was impressed with your report and ordered the same unit from Bit Deals for my caravan.

The unit has happily performed all of my work bench tests and I am ready to install it into the van.

I'm curious if you were able to connect an earth neutral bond or if you made do with the floating neutral from the inverter output?

Thanks,
Jordan

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Re: Is anyone using an arc welder with an offgrid system

Post by doggy » Tue, 24 Sep 2019, 13:27

Hi Jordan,
I added:

a. Neutral link to ground.
b. Ground to existing house ground (copper stake).

Incidentally, Hary who started this thread has successfully used his with his arc welder.

Cheers,
Dave

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Re: Is anyone using an arc welder with an offgrid system

Post by BaronVonChickenPants » Tue, 24 Sep 2019, 14:27

Thanks Dave,
I was hoping to connect this way, just wanted to check someone else had done it first before I let the smoke out.

Regards,
Jordan.

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