Lifepo4 fully discharged... can it be revived?

Kind of as I suspected as soon as I saw the heat sink looking appearance, internal controller, pulling plastic cover in back reveals BMS. Took readings at the pins, here's what I came up with by starting at one end of the pins and moving them over one position at a time, left to right:
4.1
4.1
4.1
3.8
3.8
0.0
3.8
3.7
3.7
3.7

I see the first row of 5 cells, what kind of cells are these things? ( Like I said before I have zero experience with Lifepo4 cells)
 
Raisedeyebrows said:
4.1
4.1
4.1
3.8
3.8
0.0
3.8
3.7
3.7
3.7
That cell could be totally dead, with a bad channel in the BMS having drained it down (balancer stuck on) or it could be a broken sense wire or bad contact. You can check for that with the meter on Ohms and measuring between that point and the actual cell it's connected to.


On the other cells...they're all pretty high for LiFePO4, which implies the BMS does not have a proper HVC (or it doesn't have charge-cutoff-FETs or it's wired wrong inside, using just the discharge-cutoff-connection for both charge/discharge), and that that middle cell really is dead, and it's allowing all the other cells to overcharge, until the charger reaches it's maximum voltage.

That can be a dangerous kind of failure, and with some cells and chemistries it's probably been the cause of fires, if the overcharge on a cell reaches a high enough point.

If the cells continue to drop in voltage as you leave the battery off the charger, then it means the BMS at least does have balancing circuitry that is working on those cells, and it should eventually drop them to about 3.3 to 3.6v each, so they're all the same voltage. That could take hours to days, depending on how overcharged they are.


As for what cells those are, there's lots of different ones, so who knows? There might be markings on them that may come up in a web search, but probably you won't find one quite the same, though you might find one that will fit in the casing in the spot the old one did, that's got specs close enough to make it all work, if you do have to replace a cell.
 
Appears I was not getting a good reading off #6, upon trying to really make sure I was getting connection with the pins it is also 3.8, revised readings:

4.1
4.1
4.1
3.8
3.8
3.8
3.8
3.7
3.7
3.7
 
amberwolf said:
Raisedeyebrows said:
4.1
4.1
4.1
3.8
3.8
0.0
3.8
3.7
3.7
3.7
That cell could be totally dead, with a bad channel in the BMS having drained it down (balancer stuck on) or it could be a broken sense wire or bad contact. You can check for that with the meter on Ohms and measuring between that point and the actual cell it's connected to.


On the other cells...they're all pretty high for LiFePO4, which implies the BMS does not have a proper HVC (or it doesn't have charge-cutoff-FETs or it's wired wrong inside, using just the discharge-cutoff-connection for both charge/discharge), and that that middle cell really is dead, and it's allowing all the other cells to overcharge, until the charger reaches it's maximum voltage.

That can be a dangerous kind of failure, and with some cells and chemistries it's probably been the cause of fires, if the overcharge on a cell reaches a high enough point.

If the cells continue to drop in voltage as you leave the battery off the charger, then it means the BMS at least does have balancing circuitry that is working on those cells, and it should eventually drop them to about 3.3 to 3.6v each, so they're all the same voltage. That could take hours to days, depending on how overcharged they are.


As for what cells those are, there's lots of different ones, so who knows? There might be markings on them that may come up in a web search, but probably you won't find one quite the same, though you might find one that will fit in the casing in the spot the old one did, that's got specs close enough to make it all work, if you do have to replace a cell.

I'm waiting to see if the BMS is doing anything as far as balancing the cells is concerned. After 2-3 good hours still have 3 cells sitting at 4.1
 
BTW, if there are only 10 cells, then it's not a 36v battery if it's also LiFePO4. That would be regular Li-Ion (LiCo, LiMN, NMC, LiPo, etc).

You should confirm this with whatever info you have about the battery.

In that case, it changes most of what I said above.

it means that none of the cells are yet fully charged, but that the three highest ones will have to drain down a fair bit to match the others, during balancing, while it's on the charger.

If it is Li-Ion, I'd leave it plugged into the charger so it can keep charging up the cells, and see if the BMS keeps draining down the high ones whenever the charger shuts off due to the BMS shutting off teh charging port.

It could take days to weeks to fix the imbalance, depending on how low the balancing current the shunts in the BMS are able to do.
 
The only thing I could find about the batteries in Ecobike was this from some outfit that offers rebuilding services on them:

LiFePo4 Li-ion
36V/8Ah

The cells are rectangular, appear to be Lifepo4. The cells that were reading high did not seem to drop over the afternoon, I then plugged the multi-pin plug in carefully making sure it was connected properly, screwed the battery back together, tested the voltage at the discharge plug again, same reading. I stuck the battery back on the bike and went ahead and rode around for a while to drop the pack's voltage down quite a bit. For some reason it seemed to have more power, climbed three very steep hills readily with no shut down (hmm?) .

After riding around for a while I tested the discharge port again, it was 36.7. I then went ahead and plugged the charger into the pack out in the driveway in a safe area on the concrete thinking if for some reason the BMS plug wasn't getting good connection before on a couple cells it might now have proper connection and balance the pack.

If I don't get any balancing action out of the BMS I think I'll pull the whole pack out of the case so I can examine every wire and test everything thoroughly. Thanks for your help AWolf, if you were anywhere near me I would gladly pay you to guide me through diagnosis and testing.
 
Raisedeyebrows said:
LiFePo4 Li-ion

While technically all of the Lithium cell chemistries are Li-Ion, many (most) batteries labelled one of those is not also labelled the other, as they are used as terms to distinguish specifcally between LiFePO4 and non-LiFePO4 chemistries.

So if it's labelled as both, you'd have to find the cell markings and see if any info comes up on those anywhere on the internet.

If it is indeed LiFePO4, then all the cells are overcharged, and the charger itself is either defective or is the wrong one for that pack. Also, the BMS is either the wrong one or is itself defective, allowing the cells to charge up that high.

It would not be the first pack shown on ES to have cells of one chemistry and a charger and/or BMS that are incorrect for the cells actually used in the pack. :/



The cells are rectangular, appear to be Lifepo4.
What markings on the individual cells show that they are LiFePO4?

Note that there are no external physical characteristics or appearances that can show you which chemistry a cell is. They can be any shape, size, connection / terminal type, color, etc.



The cells that were reading high did not seem to drop over the afternoon, I then plugged the multi-pin plug in carefully making sure it was connected properly,

Ah--well, if they're not plugged into the BMS, they won't drop because theyr'e not connected to the balancing resistors, which is what drains them to make them drop in voltage.

If they *did* drop without being connected to anything, then that would mean they're defective and self-discharging and would need to be replaced. ;)

For some reason it seemed to have more power, climbed three very steep hills readily with no shut down (hmm?) .
Was it also left on the charger for a while prior to this (which would let the cells get more charge in them and perhaps balance a bit)?

If not, then I suspect there is a poor connection at that cell that read 0V, creating enough of a resistance that the BMS read taht cell as lower than it really was, and shutting off when under load. There could also be other connetions that were not very good, in that sense connector.

Could be caused by anything from a bit of oxidation on the contact surfaces, to contacts spread apart a tad too far, to bad crimps between wire and contact, to bad solder joints on the BMS board.


Thanks for your help AWolf, if you were anywhere near me I would gladly pay you to guide me through diagnosis and testing.

If you were close, I'd be happy to help without pay; it's good to help people and to keep ebikes on teh road (especially if they replace a car :) ).

Buuut...I do take contributions for experiments or doggie food, etc., at the link in my signature. ;)
 
amberwolf said:
Raisedeyebrows said:
LiFePo4 Li-ion

While technically all of the Lithium cell chemistries are Li-Ion, many (most) batteries labelled one of those is not also labelled the other, as they are used as terms to distinguish specifcally between LiFePO4 and non-LiFePO4 chemistries.

So if it's labelled as both, you'd have to find the cell markings and see if any info comes up on those anywhere on the internet.

If it is indeed LiFePO4, then all the cells are overcharged, and the charger itself is either defective or is the wrong one for that pack. Also, the BMS is either the wrong one or is itself defective, allowing the cells to charge up that high.

It would not be the first pack shown on ES to have cells of one chemistry and a charger and/or BMS that are incorrect for the cells actually used in the pack. :/



The cells are rectangular, appear to be Lifepo4.
What markings on the individual cells show that they are LiFePO4?

Note that there are no external physical characteristics or appearances that can show you which chemistry a cell is. They can be any shape, size, connection / terminal type, color, etc.



The cells that were reading high did not seem to drop over the afternoon, I then plugged the multi-pin plug in carefully making sure it was connected properly,

Ah--well, if they're not plugged into the BMS, they won't drop because theyr'e not connected to the balancing resistors, which is what drains them to make them drop in voltage.

If they *did* drop without being connected to anything, then that would mean they're defective and self-discharging and would need to be replaced. ;)

For some reason it seemed to have more power, climbed three very steep hills readily with no shut down (hmm?) .
Was it also left on the charger for a while prior to this (which would let the cells get more charge in them and perhaps balance a bit)?

If not, then I suspect there is a poor connection at that cell that read 0V, creating enough of a resistance that the BMS read taht cell as lower than it really was, and shutting off when under load. There could also be other connetions that were not very good, in that sense connector.

Could be caused by anything from a bit of oxidation on the contact surfaces, to contacts spread apart a tad too far, to bad crimps between wire and contact, to bad solder joints on the BMS board.


Thanks for your help AWolf, if you were anywhere near me I would gladly pay you to guide me through diagnosis and testing.

If you were close, I'd be happy to help without pay; it's good to help people and to keep ebikes on teh road (especially if they replace a car :) ).

Buuut...I do take contributions for experiments or doggie food, etc., at the link in my signature. ;)

A couple posts up you'll note I did determine I got a false reading on the cell I thought was reading 0.00, after trying again and making certain I had got the probes in on that one it also read 3.8

I see no visible markings on the cells I can see, I'm curious what they are now, I was not aware there are Li-ion cells in a rectangular format. I'll keep a close eye on the pack this evening with the charger on it (which was evidently the one sold with the bike when new but it wouldn't suprise me if it wasn't the correct one having seen what some of the Ebike manufacturers out there in the world are capable of).
 
My guess is with 10 cells 36v and being charged to 4.1v it is nmc lipo or ? I do not belive they are lifepo4 (10s )as they my have gone puff or soon will. Lifepo4 has a lower fire danger but can still make fire. Will all the stored energy.
 
999zip999 said:
My guess is with 10 cells 36v and being charged to 4.1v it is nmc lipo or ? I do not belive they are lifepo4 (10s )as they my have gone puff or soon will. Lifepo4 has a lower fire danger but can still make fire. Will all the stored energy.

I can only see the first row of five cells which appear to be flat rectangular in metal cases. I would like to pull everything out of the case in the next day or two, I will try to be extremely careful and do it out in the middle of the driveway.
 
If this was a lifepo4 36v battery it would have 12 cells in series, the fact it has 10 indicates it is Lithium polymer if pouch cells or li-ion if cylindrical cells both different chems to Lifepo4.
Max cell voltage 4.2v, min discharge 3.3 - 3.6 depending on the chemistry.
The 10 reading simply indicate thta the battery is very much unbalanced and needs balancing to see if it will hold steady cell voltages.
 
hemo said:
If this was a lifepo4 36v battery it would have 12 cells in series, the fact it has 10 indicates it is Lithium polymer if pouch cells or li-ion if cylindrical cells both different chems to Lifepo4.
Max cell voltage 4.2v, min discharge 3.3 - 3.6 depending on the chemistry.
The 10 reading simply indicate thta the battery is very much unbalanced and needs balancing to see if it will hold steady cell voltages.

Well we'll find out shortly when I pull the cells out, I just have never seen Lipo batteries in metal cases like that with fixed metal terminals, this has been a learning experience for me, I'll be interested to see what they say.
 
Managed to push the pack out of the case being as careful as possible, got it started by pushing with my foot on the bottom, shoved it through with a 12" piece of 2x4" wood.
sJa5AUZ0ES.JPG

The rectangular cells are banded together.
eyiIdNj=Ux.JPG

Pulled wires and taped them off, preparing to snip banding to identify and inspect cells. Likely at least some of these things are headed for the electronics recycling facility where I ditch all my bad cells.
rMPkdi3uGX.JPG


Would someone educate me here, what is the bigger board with the heatsink and mosfets and what is the smaller board? I was assuming the smaller of the two is the BMS and the one with the heatsink was a small internal controller. I notice the bike has another controller of some sort down in a compartment in the bottom bracket area under the battery connections.
 
amberwolf said:
999zip999 said:
They make all the cameras trees in all different formats

What are "Cameras trees"?

Yeah I'm wondering the same thing, I've seen Cell Tower Trees of all different varieties looking like fir trees, palm trees, redwood trees, maybe a type of camera battery?
 
Label on the outside of the pack
Y6cvxgdcRx.JPG

Went ahead and snipped the banding on one of the groups of 5, indeed packs are puffed. Taped back together and left them out on the concrete in the driveway. Can someone advise a safe disposal method? Would you advise carefully separating the cells, putting in box and transporting to recycling center?
BHtLoYOuIY.JPG
 
I was sitting in the dentist office waiting my turn.
(They make all cells in all different formats.)
Sorry I thought I read before posting.
 
If puffed and lifepo4 cells at 4.1 volt an old 5 gal. Bucket with water and add salt it bubble up a weird color and zero the cell.
But with 10 cells and a 41.0 volt charger I think is different chemistry
 
999zip999 said:
If puffed and lifepo4 cells at 4.1 volt an old 5 gal. Bucket with water and add salt it bubble up a weird color and zero the cell.
But with 10 cells and a 41.0 volt charger I think is different chemistry

Phylion prismatic cells, type used in Ezeee bikes at some point evidently. I know zero about prismatic cells.
 
Raisedeyebrows said:
Would someone educate me here, what is the bigger board with the heatsink and mosfets and what is the smaller board? I was assuming the smaller of the two is the BMS and the one with the heatsink was a small internal controller. I notice the bike has another controller of some sort down in a compartment in the bottom bracket area under the battery connections.


Agree the smaller one looks like the BMS as it has individual cell connections. If you can take a more close-up picture of the large board, I could make a better guess. I have not seen something like that in a pack before.
 
The bigger board
y0CupQ8RyJ.JPG

vMb4!hmd0F.JPG


Yes I am curious what it is, I assumed it was an internal controller initially due to the 3 chips and the heat sink on the back, I then got curious what was in the compartment on the bottom bracket of the bike directly under where the battery sits and there is what appears to be a controller. Made me wonder why the bike would have 2.
 
A search on Phylion Prismatic cells turned up this photo posted by ypedal on his blog
RsjAltZjwC.JPG

Caption:

"Puffed Phylion cells from eZee battery packs of years ago.. they lasted about 2 years of use and then quit, used or not… thank god they changed suppliers ..."
 
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