Discover AES LiFePO4 Battery with one dead cell- Is it possible to repair?

[208stephen]

I suppose having the original purchaser register and do warranty is out the window? or if it was never register pretend you are the original purchaser?

Yes, it's definitely not possible to warranty, especially since I've taken it apart

 

[208stephen]

Done, dead.

It is possible to feed them voltage but it could be very dangerous.
There is one or more cells in that group with an internal short that bled out the rest in that group. This could result in fire if you charge them.
If you dont find this cell(s) It is a hopeless project.

Your only option is to find an identical group (very unlikely)
Or spot weld your own group. Ideal it could fit back in the case

Or use it as a 15s battery. You would need to wire up a different BMS to do this. This could be beyond the scope of your comfort and experience.
I have built battery banks out of 18650s in the past and have a spot welder. Its not too terrible. You could never reuse those nickel buses tho. It will be destroyed if you try to remove the cells from it.

The problem with cheap spot welders is that they rarely have any way to have 3 deep as the welder part is fixed. You would need a spot welder that has a hand held welder.

You could perhaps look at Batteries Plus, I have heard they can repair power tool batteries. The same machine that can do that could most likely help you.

Thanks. I really appreciate your suggestions.

 

[208stephen]

Would it be possible to replace all 15 cells in that string? It looks like to get in there I would have to break all the spot-welds, hopefully preserving the tabs on the busbar. Is there a good technique to do that?
26650 cells seem pretty common and inexpensive. What would be the technical obstacles to doing this?
It does seem pretty involved but in the context of possibly repairing a $3000+ battery that would otherwise be garbage.....
Thoughts? Has anybody tried to do this?

 

[ScrotusGobbleBottom]

context of possibly repairing a $3000+ battery that would otherwise be garbage

Not true at all if you got a BMS like https://www.18650batterystore.com/products/jk-b2a24s15p-bms and run with 15s

I run 15s and it is just fine.

The only reason not to toss the whole group is if you were to rip it all apart and charge all the cells individually and watch the resistance. After this you would NEED to put them in a safe location that is fireproof and watch for the individual cells unconnected voltage to drift apart. After about 3 weeks it should be apparent which cells are leaking by comparing voltages. Those are the bad/dangerous ones.
If you are not prepared to do this, the whole group is junk.

If you are planning on replacing the bad cells you will need to spot weld new nickel strips to the new cells no matter what. With this in mind it wouldnt be hard to do the rest. Attempting to preserve the original nickel strip is not worth it. Yuu need to dismantle all 15 cells FROM EACH OTHER in order to rule out the bad ones. Even after you find the bad ones, the remaining ones are damaged. To what extent you will not know without capacity testing all of them individually. If the cells are at zero volts they are very stressed and you could have introduced NEW internal shorts that could derail your whole plan and waste all of your time.

 

[208stephen]

So I would replace the Discover BMS with the JK?

I was thinking that I would replace all 15 cells of the group. I was under the impression that once they sit at 0.0V for awhile they're not recoverable(?)

 

[ScrotusGobbleBottom]

once they sit at 0.0V for awhile they're not recoverable

Yes, more or less not worth it and dangerous to use even if everything looks ok.

So I would replace the Discover BMS with the JK?

I was thinking that I would replace all 15 cells of the group

These are 2 good options. If this battery is alone, with no other batteries in parallel, you could buy the JK BMS and wire it up yourself. This might not be too easy. You would need to either find the balance cables and correctly splice them to the new BMS. Any mess up here could ruin the BMS. You need to know what you are doing. Please do your homework and wear safety glasses any time your are messing with any battery system.

Buying and spot welding a replacement would probably be easier. The hard part of this is finding a good spot welder. It would not be worth it to me pay $200 for a welder and $300 for 26650's. Also it might not be easy to find a shop to help. I doubt that every Batteries Plus shop has a spot welder.

I would buy the JK BMS. Just my opinion. It depends on how much money you want to spend to make the battery not more ewaste and preserve your investment.

 

[208stephen]

Yes, more or less not worth it and dangerous to use even if everything looks ok.



These are 2 good options. If this battery is alone, with no other batteries in parallel, you could buy the JK BMS and wire it up yourself. This might not be too easy. You would need to either find the balance cables and correctly splice them to the new BMS. Any mess up here could ruin the BMS. You need to know what you are doing. Please do your homework and wear safety glasses any time your are messing with any battery system.

Buying and spot welding a replacement would probably be easier. The hard part of this is finding a good spot welder. It would not be worth it to me pay $200 for a welder and $300 for 26650's. Also it might not be easy to find a shop to help. I doubt that every Batteries Plus shop has a spot welder.

I would buy the JK BMS. Just my opinion. It depends on how much money you want to spend to make the battery not more ewaste and preserve your investment.

I have 6 of these batteries currently and ideally would like to ad this battery if I can repair it. I have a Lynk 2 that allows me to monitor the batteries and I'm assuming would not interface with the JK BMS.

 

[ScrotusGobbleBottom]

would not interface with the JK BMS.

correct. most likely not compatible.

 

[ElectricIslander]

correct. most likely not compatible.

Probably best bet is to find an EV battery repair shop that has the necessary spot welder and experience with larger battery packs. This battery would probably be quite easy for them to figure out. Must be some automotive EV shops in your area?

You might reach out to Discover and request purchasing the specific battery part that you need now that you have figured it out. That way their liability might not be as much.

Could you arrange to ship the battery back to them for them to repair?

I'm a bit concerned about Discover's reluctance to support their products given that I just ordered a significant number of their batteries.

Send me a PM and I can discuss further options with you.

 

[208stephen]

It looks like I'm running out of options so I'm leaning towards going into the unit and replacing all 15 cells with new ones. I know that they are 26650 cells, 3.2V, 3.8aH. Does anybody out there know what brand cells that Discover uses in their batteries? How important is it to use the same brand?

Any advice on breaking spot welds?

Any advice on a reasonably priced spot welder?

 

[ElectricIslander]

It is relatively easy to make a spot welder from an old microwave magnetron transformer. There are several Youtube videos!

You can also make a spot welder attachment for a conventional welder.

 

[ScrotusGobbleBottom]

An an old microwave magnetron transformer can kill you if you touch the wrong thing even while unplugged. Be careful with this idea.

 

[ElectricIslander]

The Youtube videos show you how to take the windings off the transformer in order to make a spot welder. The idea is to make it into a low voltage high current power supply which makes the transformer safe to use. Do be careful though!

 

[208stephen]

I finally made some time to get into this battery. Today I removed the busbars for the bad cell. The busbars themselves are in good shape but the metal tabs that were spot-welded to the batteries didn't fare so well.

Now that the individual cells are isolated is there any way that I can test for a bad cell(s) without opening up the plastic casing?
Or, since they all read 0.00 volts, are they all bad and in need of replacing? I have found a warrantied Discover Battery that I may be able to recycle good cells from.

The busbars have thin sheets of metal spot-welded to them with 2 tabs for spot-welding to the batteries (see photo below). Are these strips a proprietary Discover item or are they a standard item that's available and that could be replaced?

If they're not available, and I decide to replace all the cells, what would be the best way to spot-weld the batteries to the busbar?

 

[208stephen]

I got the case open this morning and removed all 15 batteries from the bad string. It's pretty clear that one of the cells was defective (shorted?). Looks like it got hot and started leaking. Here are some pictures of the one damaged cell next to an intact cell.

 

[208stephen]

And here's a picture of the only marking on these cells. Anybody have any idea about what brand they are or how I might find out.
I've asked Discover directly, but apparently it's "top secret". WTF?

 

[underdog5004]

I've done what you're trying to do. This was with a discover AES 6.4 KW battery I think. The design of that battery something like 24 cells in parallel then 16 in series. The connections between cells are not bus bars but were circuit board material I guess with a lot of conductive material in it. There are holes in these boards and the cells had male and female screws/threads on them so you could rotate the cell through the hole to lock with the next cell. I pulled out all the cells and tested every single one of them I removed about eight or nine cells which showed a zero voltage and then reconfigured the battery with fewer cells in parallel but the same number of parallel groups in series. It was not difficult but it was a lot of work. The trickiest part was removing and reinstalling the outer case. I put the battery upside down on a sheet of thick honeycomb cardboard then lifted with a forklift on straps that were wrapped on the handles of the outer case of the battery. I had to do a little jiggling to get the inner works to slide out of the outer case. There was an arc when I did this but it was momentary and did not seem to affect the battery later. When I put the reassembled in our works back into the battery case I wrapped the edges of the outer case with a non conductive tape to help prevent arcing. After I put the battery together I noticed that it seemed to think it was discharging all the time this was a problem with the internal shunt being tightened too much. I loosened the nuts a little bit and then it began reading current properly. I never really used this battery it was more for fun and as far as I know it's still working. I did all this work at a solar shop I was working at the time they were very understanding. These are cool batteries but I don't like the arrangement of many many parallel cells without fusing. I forget the exact number on the side of the cell but I recall them being 5,000 milliamp hours possibly 5,500 milliamp hours. I did find replacement cells on Amazon but never ordered them because there was no need.

 

[208stephen]

Thanks for your reply. It sounds like their bigger batteries have a different kind of construction. Threaded terminals would be much easier to deal with. For me to put my battery back together I'll have to buy a spot welder and learn how to use it.

The cells that had 0 volts you threw away or were you able to recharge and use them? It's interesting that the defective cells didn't take the others down. Were the 8 or 9 bad cells all in the same string of 24?

I've only surgically removed one string of 15 cells from a "panel" that has 4 strings total. There are 4 "panels" in total and all the rest of the cells are holding a resting voltage of 3.32-3.5V.

 

[underdog5004]

Thanks for your reply. It sounds like their bigger batteries have a different kind of construction. Threaded terminals would be much easier to deal with. For me to put my battery back together I'll have to buy a spot welder and learn how to use it.

The cells that had 0 volts you threw away or were you able to recharge and use them? It's interesting that the defective cells didn't take the others down. Were the 8 or 9 bad cells all in the same string of 24?

I've only surgically removed one string of 15 cells from a "panel" that has 4 strings total. There are 4 "panels" in total and all the rest of the cells are holding a resting voltage

I removed the zero volt cells and did not try to charge them again. there was some leaking electrolyte in the case like a brown fluid that smelled incredibly bad. The zero volt cells weren't all in the same Parallel Group but they were in the same volumetric area. Yeah I don't recall that the zero volt cells brought the other ones down but the battery had been brought in because it would come up to voltage but then go to zero when a load was applied. Discover warrantied that battery and told the shop I worked for to dispose of it responsibly. I figured the most responsible thing was to recover as much energy storage capacity as possible. If I had to guess I would say that the cells were 32550 sized but I don't recall it was several years ago.

 

[underdog5004]

I removed the zero volt cells and did not try to charge them again. there was some leaking electrolyte in the case like a brown fluid that smelled incredibly bad. The zero volt cells weren't all in the same Parallel Group but they were in the same volumetric area. Yeah I don't recall that the zero volt cells brought the other ones down but the battery had been brought in because it would come up to voltage but then go to zero when a load was applied. Discover warrantied that battery and told the shop I worked for to dispose of it responsibly. I figured the most responsible thing was to recover as much energy storage capacity as possible. If I had to guess I would say that the cells were 32550 sized but I don't recall it was several years ago.

Also as I recall I had to take out a few good cells as well as all the bad ones I found so that each Parallel Group had the same number of cells in it. In my mind the smaller 5 amp hour cells aren't worth working with when you can get larger much larger Prismatic cells at a relatively low price. The problem with using multiple low capacity cells is that the hardware overhead grows so you end up spending as much if not more than if you had just used fewer larger capacity cells.