Are these batteries usable?

[dragondoom295]

I picked these up from a recycler. I think they are Lifepo4 chemistry. Looks like maybe they were in a fire of some kind (rust on the bottom of each case, one melted cable). I have 6 of them. One is open and I tested the charge between a couple of the series. The batteries have a charge, but the breaker doesn't turn on the lights on front. Maybe the BMS cut power for low voltage? I cannot test the others without opening them up. The recycler said the green led lights were on when they got them. I'm new to the whole battery and solar thing. What do you suggest I do from here? I'm out of my depth I think, but if I can get some cells or use them it will be a great deal.

 

[NimrodthePixieWrangler]

If the units don't turn on and all the cells are above the cutoff threshold and the electronics do not appear to be fixable I would begin the process of removing all the electronics and BMS. Testing every cell with at least a volt meter, then load/ discharge test and some charging. Preferably at least one full discharge/charge cycle within acceptable voltages. Then once the cells check out, find replacement parts for all the components you removed and rebuild them. Always keeping in mind that damaged cells can lie dormant for months before going off catastrophically. I've seen batteries that underwent a controlled burn test light off again 5 weeks after the test.

Edit: If cells are below a cutoff threshold and the electronics appear to be in good condition you can apply a low current 48v source to the external lugs and try to charge them enough that the BMS wakes up. If its so dead the BMS wont wake up sometimes you can revive cells by trickle charging them up at the cell level with a controlled power supply to wake up the cell to the point the BMS can take over. All of this is advanced battery work and should be done in a safe area where if they go up in smoke it wont take anyone out or burn a building down.

 

[dragondoom295]

Thanks. I think disassembly and testing each cell will be how I have to proceed. This is one of the worst looking ones. Cells on the bottom are not reading voltage, but the others appear to. Maybe break each unit down, test the cells, salvage what components I can and go from there. Voltage of the cells above the rusted part is around 3.2v. BMS appears in good condition.

 

[OffGridInTheCity]

Can't tell for sure but they look like 18650 NMC rather than LifePo4 - e.g. 4.2v max charge. To see their state I'd try to figure out what cell they are and get 'new' specifications and test for capacity - e.g. >80% original capacity would indicate a lot of life left. Also try to balance and check for any significant self discharge.

Alternately you could tear it apart and fully test each cell (and be 100% sure of things) and then re-assemble into a DIY battery - but not sure that's what you have in mind.

 

[sollap]

The Storz Power LFP48100-5kwh is a LifePo4 battery. Also sold under the HUMLESS brand name. There's probably some good batteries there if you have the time to tear them down, clean them up, and mix-match the working parts.

 

[NimrodthePixieWrangler]

They do make cylindrical cell LIFEPO4 chemistry but they are not common. Knowing the chemistry of the cells is important to determine the charge/discharge voltage levels.

If a single cell is damaged it will drain the whole set of parallel cells down with it causing damage to all unless it blew the fusible links. For the most part I would leave all the pack level wiring(bus bars?) complete. Teardown to individual cells is probably an unnecessary labor for a group of cells that is very likely totally damaged. Keep cells wired as they are in the pack. Just rewire up to the original pack connections if you end up doing the testing/rebuild route.

After seeing your board pictures I should say I have seen failed water damaged Ryobi BMS pull several cells of a pack down to absolute zero and it killed the cells.

 

[dragondoom295]

Thanks all. It is a 16s100a BMS, so lifepo4? From everyone's input, sounds like the best start is to tear down to pack level (nominal 3.2v?) and start testing from there. I will look on YouTube for guides, but I can test each pack by going through a discharge/charge cycle and see if it holds the correct charge voltage (depending on chemistry)? If any packs don't hold a charge, is it worthwhile to tear those ones down to cell level and test each cell?

 

[OffGridInTheCity]

Thanks all. It is a 16s100a BMS, so lifepo4?

If it's 16s, then that's a good guess but....

From everyone's input, sounds like the best start is to tear down to pack level (nominal 3.2v?) and start testing from there. I will look on YouTube for guides, but I can test each pack by going through a discharge/charge cycle and see if it holds the correct charge voltage (depending on chemistry)?

You need to figure out what kind of cells and the XsYp before doing any charging. This will tell you what kind of charger you need. Above all, you do not want to *overcharge* lithium-ion cells.

A battery (from the pic above) will have groups of parallel cells hooked in series - s (series) and p (parallel). For example, if you have 16s (16 parallel groups of cells in series) and each parallel group has 10 cells then you have 16s10p = 160cells total. You can look at how they're hooked up, and count them to figure the s and p.

Look at the battery casing to see if it says LifePo4 and/or ah or wh. If that fails, look at the individual cells and find the labeling and look up the specs for it. Post detailed pics of the casing and/or cell labels and folks here can try to help with identifications.

If any packs don't hold a charge,

From you're description, these are16s batteries (not packs) according to you're comment above. When testing a 16s battery, you need to have a working 16s BMS else you might over-charge one or more of the parallel groupings in the 16s.

is it worthwhile to tear those ones down to cell level and test each cell?

Cell level? That's a whole different effort than testing a full battery (16s).

I would suggest you consider whole battery approach first....
- Figure out the cell type (possibly LifePo4) and figure out the XsYp and total number of cells. You *must* be sure what you have - NMC or LifePo4 before proceeding with any testing.
- The battery case may have an overall ah or wh description - and you can infer the capacity of each cell by dividing the number of cells into the overall battery ah or wh. Look at any writing/labels on the individual cells - and lookup the specs / capacity. This + the XsYp will give you critical details to test capacity.
- You'll need a Xs charger and a Xs BMS. You may also need an individual Xp (cell) charger if they groups of parallel cells are way out of whack.
- You'll need a discharge load / measurement method to get the capacity.
- A BMS will help find Xp (group of parrallel) cells that won't stay balanced - e.g. possibly due to self discharge.

If you tear it apart to do cell level then you need to think individual cell level tester / charger + re-assembly - it's a different scenario and an order of magnitude more work.

 

[AntronX]

I picked these up from a recycler.

How does one approach a recycler to get things like scrapped inverters or batteries? Do you just show up and ask if they would sell them to you?

 

[dragondoom295]

How does one approach a recycler to get things like scrapped inverters or batteries? Do you just show up and ask if they would sell them to you?

It was on the offer up app. I didn't realize they were so damaged.

 

[dragondoom295]

Thanks again. I'll get some more info on the cells once I can open up the metal case some more.

Another question, when I get to this point, what is the best way to go about cleaning off all the corrosion and rust on the bottom/back cell (see pic)?