Charging Headway Cells below 1.0v with Power Supply

[Nikg736]

I've got some 8ah Headway cells that are at about 0.9v, some at 1.1v and some at 2.5-3.0v.
I have an adjustable benchtop power supply (30v, 10A).
I also have some busbars that I can connect up to 12p.
What is the best and quickest way to charge these and would there be a different method for charging the lower voltage cells vs. the higher voltage ones?

I was thinking for the lowest voltage ones to just put them in 12p, set power supply to 3.6v and crank up amps as high as they will go.
Or would it be better to connect in series like 4-8s and set voltage equal to 14.4v - 28.8v? Then after the series charge connect them in parallel to top balance and charge to 3.6v

I've never used a PS to charge before, so I also need some help with the correct order of things. I think I set the voltage first with nothing hooked up and then connect, yes?

Thanks

 

[sunshine_eggo]

I've got some 8ah Headway cells that are at about 0.9v, some at 1.1v and some at 2.5-3.0v.
I have an adjustable benchtop power supply (30v, 10A).
I also have some busbars that I can connect up to 12p.
What is the best and quickest way to charge these and would there be a different method for charging the lower voltage cells vs. the higher voltage ones?

I was thinking for the lowest voltage ones to just put them in 12p, set power supply to 3.6v and crank up amps as high as they will go.
Or would it be better to connect in series like 4-8s and set voltage equal to 14.4v - 28.8v? Then after the series charge connect them in parallel to top balance and charge to 3.6v

I've never used a PS to charge before, so I also need some help with the correct order of things. I think I set the voltage first with nothing hooked up and then connect, yes?

Thanks

Charge the low ones (< 2.8V) individually at a very low rate - like 0.01C at most. Once they can hold 3.0V on their own, blast away.

Once you've addressed all the low ones, parallel away.

Make sure you mark the low cells so you don't lose track of them.

A YR1030 or YR1035+ would be very useful in checking cell impedance.

 

[Nikg736]

So...no good to get a dozen that are at 0.85v-0.90v, hook them parallel and charge at 1A? That would be about 0.01C if I am not mistaken.
12 cells x 8ah each = 96ah. So 1C would be 3.6v at 96A. So 0.1C is 9.6A and .01C is .96A.

I've got quite a few of these to try to bring back to life, so is it reasonable to at least put a bunch of these in parallel for a while first to get some charge into them? Then disconnect, let rest, check voltage and take similar ones and put them back in parallel for another round?

 

[sunshine_eggo]

So...no good to get a dozen that are at 0.85v-0.90v, hook them parallel and charge at 1A? That would be about 0.01C if I am not mistaken.
12 cells x 8ah each = 96ah. So 1C would be 3.6v at 96A. So 0.1C is 9.6A and .01C is .96A.

I've got quite a few of these to try to bring back to life, so is it reasonable to at least put a bunch of these in parallel for a while first to get some charge into them? Then disconnect, let rest, check voltage and take similar ones and put them back in parallel for another round?

Those cells need to be evaluated individually. When doesn't matter. If you parallel several, you'll have to unparallel them to assess if they can hold voltage, AND while charging, if one can't hold charge, it may impair the whole process.

If you're in a hurry, start with the cells over 2.8V and parallel/charge with wild abandon.

 

[Nikg736]

Those cells need to be evaluated individually. When doesn't matter. If you parallel several, you'll have to unparallel them to assess if they can hold voltage, AND while charging, if one can't hold charge, it may impair the whole process.

I figure I will parallel a whole bunch at a time...maybe even 24 at a time all in parallel just to get some voltage in them. I have busbars that I can use to connect up to 12 in parallel at a time, but I can also put a busbar between those to make 24p.

Is there any danger in using the following regimen, and do I need to separate the ones at 1.05v from .85v? Or should I just make two groups separated by above/below something like 2.0v to 2.8v? (I picked 1v simply because I had seen that mentioned in many other threads as a threshold above or below which LFP cells had problems.)
1. Separate cells into 3 groups by voltage: (0.85-0.99) (1.0-1.1) (2.5+)
2. Put 12-24 in each grouping in parallel with busbars
3. Set voltage on PS to 3.6v, connect to parallel cells, adjust amps to somewhere between 1-2A (could this be higher without consequence?)
4. Charge for ?? (an hour, until volts go over 2.8v, some other criteria?)
5. Disassemble, (let rest?), check voltage again
-cells that go back below 1v probably no good?
6. Cells over 2v (or 2.8v?) get put back in parallel to see if they will charge up fully. Now increase amps to as much as possible.
7. Repeat the process 1-2 times to further identify the "best" cells and how to use and group them for future battery duty.

 

[sunshine_eggo]

I figure I will parallel a whole bunch at a time...maybe even 24 at a time all in parallel just to get some voltage in them. I have busbars that I can use to connect up to 12 in parallel at a time, but I can also put a busbar between those to make 24p.

Is there any danger in using the following regimen, and do I need to separate the ones at 1.05v from .85v? Or should I just make two groups separated by above/below something like 2.0v to 2.8v? (I picked 1v simply because I had seen that mentioned in many other threads as a threshold above or below which LFP cells had problems.)
1. Separate cells into 3 groups by voltage: (0.85-0.99) (1.0-1.1) (2.5+)
2. Put 12-24 in each grouping in parallel with busbars
3. Set voltage on PS to 3.6v, connect to parallel cells, adjust amps to somewhere between 1-2A (could this be higher without consequence?)
4. Charge for ?? (an hour, until volts go over 2.8v, some other criteria?)
5. Disassemble, (let rest?), check voltage again
-cells that go back below 1v probably no good?
6. Cells over 2v (or 2.8v?) get put back in parallel to see if they will charge up fully. Now increase amps to as much as possible.
7. Repeat the process 1-2 times to further identify the "best" cells and how to use and group them for future battery duty.

I'm not going to give you the answer you want if you keep asking. You asked for the "best and quickest" way - these are mutually exclusive.

If your goal is to build a reliable battery, the price for buying cheap used cells is time.

I've stated my opinion. I'll repeat/elaborate.

The low ones need to be evaluated individually.
The cutoff is 2.8V, not 2.5V.
Charge should be at a very low rate, 0.01C - you can't control this with cells in parallel.
Check IR with YR1030/1035 or other consistent means. Discard outliers.

If you insist on paralleling them, I'd limit it to 4 with a current of 0.05C to insure that no individual cell sees more than that.

 

[Nikg736]

Thanks Sunshine Eggo, I will limit the parallel to 4 at a time.