Another broken stud story

[Fast1one]

Well it finally happened. After months of being careful I’ve damaged a cell with no spare available. I’m generally pretty careful and this experience has me dumbfounded.

Before you ask, I’ve never so much have hand tightened these with a nut driver. I can’t imagine going over the recommended torque ratings without leverage, much less since I am of average build and below average strength but I digress….

After capacity testing, load testing for months it was finally time to lay the cells to rest. I moved them into the bus conversion where they experienced mild temperature fluctuations of around 50F to 70F. Today I went to check the cell voltages for the final time before installing the bus bars and I found a stud just resting on the terminal, no longer welded. Note I moved the stud in the following picture to show the terminal surface:




There appears to be a complete lack of penetration on the weld. I’m guessing the (mild) torquing over the months and temperature shift finally did this in. Needless to say I don’t trust these AT ALL for an RV application and I will be ordering replacements from a different vendor. I’ll be selling these at a loss locally with a fat disclaimer of the issue.

FYI, they originally came from Shenzhen Basen Technology Co according to the label but I purchased them through an intermediary. Had I known they were coming from a seller with less than stellar ratings on this forum, I would have reconsidered.

So what’s the lesson? I’m not really sure. Definitely use a torque wrench. But I don’t think that was the problem here. Stay away from studs? I will certainly be switching to screw in terminals from Docan since I need these fast. I find the fixed length of the studs rather limiting.

These are beyond my ability to repair and likely for most DIYers. But if anyone in the central coast of California needs some cheap EVE 230AH cells I’m your man.

 

[backwoods]

no warranty? that sucks, obvious it wasn't done correctly from factory. to me at least.
jb weld and you're good to go 😜

 

[NVS]

What has anyone done to fix this issue? I'm very familiar with how these are welded on and would think this is done before the battery is made. Would it be possible to tack weld this back in place with a wire welder? I would hate to think these would just be junk if this happened.

 

[Bluedog225]

I’m sorry to say, the others are unreliable. And failure later could be dangerous.

I don’t know if they can be drilled and tapped.

 

[SparkyJJO]

doubt they could be drilled and tapped as the tapped threaded holes are something that is also welded onto the top of the cells. They aren't drilled down into the cell.

 

[Fast1one]

I’m sorry to say, the others are unreliable. And failure later could be dangerous.

I don’t know if they can be drilled and tapped.

This is precisely my thought. Which is why I will be replacing them with alternatives. The only way to properly fix them would be laser welding as far as I know.

 

[Bluedog225]

You could drill one and find out how deep the metal is. The others might be salvageable. Be careful.

 

[WindWizard]

I am sorry for your loss. It seems like such poor quality. I have purchased 48 eve 280ah from Docan Jenny Wu and have been totally impressed with the quality for the Cells. I do not even bother with capacity test. I just verify the voltage and hook them up. I have had no issues and I do not expect to have any. They deliver the quality Cells you pay for. You just cannot take a chance of the welded studs falling off the cells due to quality issues. It could cause a major catastrophe. I think it pays to purchase from a known vendor with a good reputation. I also do not do the top balance thing. It just eats up time and energy. Once the Cells get up towards 3.5 Volts then monitor them and deal with the low and the high or just run them below the knees.

 

[Fast1one]

I am sorry for your loss. It seems like such poor quality. I have purchased 48 eve 280ah from Docan Jenny Wu and have been totally impressed with the quality for the Cells. I do not even bother with capacity test. I just verify the voltage and hook them up. I have had no issues and I do not expect to have any. They deliver the quality Cells you pay for. You just cannot take a chance of the welded studs falling off the cells due to quality issues. It could cause a major catastrophe. I think it pays to purchase from a known vendor with a good reputation. I also do not do the top balance thing. It just eats up time and energy. Once the Cells get up towards 3.5 Volts then monitor them and deal with the low and the high or just run them below the knees.

Yeah there wasn’t really any indication of poor quality though. Aluminum welds are notorious for looking fine until they’re not. The QR codes are intact. Voltage curves looked similar. The cells all tested within 1-2% of eachother and all over 230AH. I guess my point is you can rely on these cells until you can’t. Once upon a time Basen had a decent reputation. Maybe Docan is different. I hope so 🤞

 

[time2roll]

I would be practicing some aluminum welding. When that fails, a shot of conductive epoxy and place them in service.
I like to fail a few times before giving up

 

[MadMax03]

Not sure I see a problem. Take it to a metal shop throw a few TIG tacks on it and call it a day.

 

[brum]

Yep, TIG spot welding will be sufficient. And if there is enough time between spots there will be no cell overheating. If this is performed by somebody with experience it will be better than the laser welding they do in the factory.

If this goes OK I would go through all cells to make sure this will not happen again.

I do not even bother with capacity test. I just verify the voltage and hook them up..

Tell me you did at least top balancing. My 4 x 105Ah EVE cells came with a 20Ah disbalance. Not something that the average BMS can take care of.

 

[WindWizard]

Not sure I see a problem. Take it to a metal shop throw a few TIG tacks on it and call it a day.

I do not know much about the TiG tacks but I think that you need access to the bottom so the current has some place to go. Looking at the Cell surface there is a flat area and then the Stud assembly which is small. There may be a small enough welding tip to get in there but where are you going to hook the ground? All you have is a flat area on the Cell.

 

[WindWizard]

Yep, TIG spot welding will be sufficient. And if there is enough time between spots there will be no cell overheating. If this is performed by somebody with experience it will be better than the laser welding they do in the factory.

If this goes OK I would go through all cells to make sure this will not happen again.


Tell me you did at least top balancing. My 4 x 105Ah EVE cells came with a 20Ah disbalance. Not something that the average BMS can take care of.

Nope I do my top balancing after the Cells are all in series and hooked together nice and pretty and the solar is charging the Cells up. The Overkill BMS just lets me know which Cells need to be adjusted and I use my automotive headlight connected to some alligator clips to discharge the Cell until it reaches the lowest Cell. And then on the other hand I take a charger and connect it to the lowest Cell and then charge it to the highest Cell. This process needs to take place when one of the Cells reaches 3.5 vollts. This process takes some time but it takes less time than the charging needed to top balance. The process is described in the Overkilll Solar manual. The Overkill BMS does not do a good job of top balancing. The discharge rate is way to small.

 

[brum]

I do not know much about the TiG tacks but I think that you need access to the bottom so the current has some place to go. Looking at the Cell surface there is a flat area and then the Stud assembly which is small. There may be a small enough welding tip to get in there but where are you going to hook the ground? All you have is a flat area on the Cell.

Put a lug on the terminal and connect it to the ground. The cells and the terminals are rated at a log higher current than the welding process needs.

 

[WindWizard]

Put a lug on the terminal and connect it to the ground. The cells and the terminals are rated at a log higher current than the welding process needs.

So you would connect the ground to the other side of the Cell and then run all the Tig current through the Cell? That may work since the Cell can easily handle 280 amps. It is certainly worth trying. You would have to make sure that the current required for the weld is going through the Cell in the correct polarity so that you did not run current backwards through the Cell. It looks like the negative terminal fell off so it may be a problem.

 

[A.Justice]

So you would connect the ground to the other side of the Cell and then run all the Tig current through the Cell? That may work since the Cell can easily handle 280 amps. It is certainly worth trying. You would have to make sure that the current required for the weld is going through the Cell in the correct polarity so that you did not run current backwards through the Cell.

The ground lug would be bolted onto the screw terminal that fell off. It would have no need to go through any part of the cell itself other than that small piece of terminal. DEFINITELY take to to a professional who has experience with aluminum though, welding something like that would be basic work for a pro.

 

[WindWizard]

The ground lug would be bolted onto the screw terminal that fell off. It would have no need to go through any part of the cell itself other than that small piece of terminal. DEFINITELY take to to a professional who has experience with aluminum though, welding something like that would be basic work for a pro.

I do not think that would work since the current has to have a path to go through. If you screw it to the lug and then where are you going to put the electrode so it has a current path?

 

[HRTKD]

I've been TIG welding aluminum for just over a year now. My welds are solid, but fugly. If this were my cell, the questions in my mind would be:
1. Weld the entire perimeter of the stud or spot weld? Welding the entire perimeter would create a lot of heat. Spot welds, not so much.
2. Filler or autogenous?
3. Cool the battery in the refrigerator before the weld to help keep the overall cell from heating up?

 

[HRTKD]

I do not think that would work since the current has to have a path to go through. If you screw it to the lug and then where are you going to put the electrode so it has a current path?

I think it would work. With the negative lead attached to the stud and the stud making contact with the cell terminal you're OK.

On my welding table, the negative lead is attached to the table, not the piece I'm welding. That's good enough.