One of my Winston cells is lame. Will a high voltage charge bring back the capacity?

[timselectric]

Or should I just call it a 610Ah battery from now on, and cut my losses??

Probably
Unless you want to replace the one cell. I don't think that I would bother. The others will probably do the same thing, just slower.

 

[Unlikely]

Wow,

Have a look at what the REC is saying the IR of the cells are, this will be a good indicator of the extent of damage.

The Winston cells do not like high temperature (above 35°C) when at high SOC. The cell bulging you see is consistent with electrolyte decomposition which is characteristic of high temperature charging.

Cycling from 4.0V to 2.7V won’t get you any cell capacity back. That cell voltage was a theoretical voltage, in practice the cells should never be held above 3.4V.

There are youtube demonstrations of removing the vent caps and releasing the cell pressure, this won’t reverse damage but will square up the cells and help with installation fixture moving forward.

If the cell internal resistances are significantly different you can use an active balancer to maximise your useable capacity.

Here is the link to the youtube video I think you are talking about. Amazing. Thanks. This might actually be sensible for me, as it means I can mount them nicely in a wooden box in the boat without changing the existing (Winston) cell connection straps. Thanks a lot !

Cells are always below 35C I would say. No heat source near them. Inverter a way above.

Yeah, I have not noticed much effect from the REC 2.5A active balancer, but then the cells never needed much before, as I would manually top balance once a year (Will Prowse style.)
I have a little heltec 4 cell balancer, but I doubt I would use it after seeing Andy OGG's results from balancing at lower voltages.
So, it looks like I have to just consider that I have a smaller battery capacity now.

I will check out Internal Resistance history, I can download that from the REC-BMS for an extended period.
How do I interpret this data?

 

[toms]

Wow,

Here is the link to the youtube video I think you are talking about. Amazing. Thanks. This might actually be sensible for me, as it means I can mount them nicely in a wooden box in the boat without changing the existing (Winston) cell connection straps. Thanks a lot !

Cells are always below 35C I would say. No heat source near them. Inverter a way above.

Yeah, I have not noticed much effect from the REC 2.5A active balancer, but then the cells never needed much before, as I would manually top balance once a year (Will Prowse style.)
I have a little heltec 4 cell balancer, but I doubt I would use it after seeing Andy OGG's results from balancing at lower voltages.
So, it looks like I have to just consider that I have a smaller battery capacity now.

I will check out Internal Resistance history, I can download that from the REC-BMS for an extended period.
How do I interpret this data?

Look for differences in the cell resistance of all the cells, if they are significantly different it indicates damage to the higher IR cells.

 

[HighTechLab]

I have 4 of these 700ah Winston cells from 2019 if anyone ever needs a spare (never used). They were a good idea on paper but boy, they are WAY too heavy to move as an assembled pack. I have zero plans to use them.

 

[Unlikely]

Look for differences in the cell resistance of all the cells, if they are significantly different it indicates damage to the higher IR cells.

Ok, so i have given all cells a nice test which took 4 days

- Constant Current 40A discharge to 2.80V then CV to 3.55V max 40A with tail current of 0.20A.
- then physically parallel the 4 cells, with supplied flexible busbars, and a slow manual top balance CV charge to 3.65V at max 5A with a tail current 0.10A

So these cells are fully charged, top balanced, and plenty of time for absorption.
They have then been disconnected and left to rest for 12+ hours.

I have then used the EBC-A40L's Resistance check function to record the cell resistances.
Two tests, each was disconnected reconnected, to avoid physical connection concerns, and tested in sequence, so each cell get a few minutes rest.
So each of the four cells was tested A.AmR; then connections made again and tested B.BmR and recorded A.A/B.BmR
You can see the test was conducted at three currents.

I would be interested if anyone can reach any conclusion from these?

I would say that these look pretty similar, within the accuracy of the Tester.
Perhaps it could be said that Cell 2 has a higher resistance, at first? But then it fell off.

Resistance after top balance

Cell 1 tested 655Ah 1.0/3.0mR @ 1A 2.2/1.0mR @ 10A 2.0/0.9mR @ 20A

Cell 2 tested 615Ah 7.0/1.0mR @ 1A 4.0/1.6mR @ 10A 2.5/2.1mR @ 20A

Cell 3 tested 655Ah 4.0/0mR @ 1A 2.0/1.6mR @ 10A 1.8/2.0mR @ 20A

Cell 4 tested 656Ah 1.0/1.0mR @ 1A 2.3/1.0mR @ 10A 2.4/1.0mR @ 20A

 

[toms]

I can’t make much sense of those results, as you say the IR isn’t significantly different between cells.

If they were mine I’d debloat them and carry on (assuming I now have a 615ah battery).

 

[Joo]

I use 100ah Winston battery on my camper van. The Winston technicians suggests setting BMS as below

Voltage-min: 2.8V
Voltage-max: 3.65V
Voltage-balance: 3.45V
Temperature-Min-charge: 0°C
Temperature-min-discharge: -10°C
Temperature-max: 50°C.