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Testing - Top Balancing Experiment - 4 cells at a time

I've never heard of Keheng.
Is this some aliX or Ebay vendor?
Michael Caro helped me get these cells. This was the beginning of summer in 2021. He recommended a couple companies. Keheng was one of them. At the time he felt they were offering the best cells and service. Although they did cost more than the other company, whose name escapes me. I went with Michael's recommendation. They arrived in excellent condition in September or early October of 2021. Per their website, they produce cells and batteries. I can tell you they do not answer emails. I've tried to communicate with them. I have yet to do a capacity test, but they seem healthy. Whether they are true 280Ah, I cannot confirm, yet. I'm hoping get what I need together to confirm that soon.
 
I explained above that top balancing just means filling each cell full.

q: Why do we top balance?
a: We top balance so that the capacity of the pack is determined by the lowest capacity cell.
Which is the best we can get.
If we don't top balance we will get less than the capacity of the weakest cell.

This part I understand.
To flesh this out with math...

280 amp hours * .7 depth of discharge / 10 amps charge current = 19.6 hours per cell

Probably a bit longer because of the constant voltage phase.
Thank you for showing me the math and how it's used to figure this type of thing out.
 
They arrived in excellent condition in September or early October of 2021.
Glad you got cells.
I can tell you they do not answer emails. I've tried to communicate with them.
Not a good sign.
I have yet to do a capacity test, but they seem healthy.
What makes them seem healthy?
Are there any dents?
Is there any swelling?
Whether they are true 280Ah, I cannot confirm, yet. I'm hoping get what I need together to confirm that soon.
Are you planning to capacity test the cells as part of commissioning?
If you have the time it would be useful.
If you test them, then you can curate the packs by capacity.

The strongest cells in battery 1.
The second strongest cells in battery 2.
The third strongest cells in battery 3.
The weakest cells in battery 4.

Do you have a capacity tester?
 
Glad you got cells.

Not a good sign.

Yeah, I tried reaching out to them twice to ask if there were torque specs for tightening nuts on the studs. Could be it doesn't translate well, but I did not receive a reply either time.

What makes them seem healthy?
Are there any dents?
Is there any swelling?

The cells are basically pristine based on many I've seen in videos. No swelling and no dents. The sheet of black plastic on the top is not glued on well in some cases, but I'm not sure that indicates anything. When I said they seem healthy I was equally referring to their appearance, and on how they all seemed to respond to exactly one hour (I timed each set of 4) of top balancing. I have them all numbered, 1 through 16. On Oct. 9th, 2022 I parallel connected 1 - 4. Then I set up the PS (following Filterguy's guide to the letter) first shorting the leads and using the course current knob I was able to achieve 9.79A current and then disconnecting the leads I adjusted the voltage to 3.55V. I applied this to 1-4 for one hour. At the end of the hour, the Mm reading at the diagonal P and N terminals was 3.314V.

I did 5-8 next. I redid the PS from scratch. This time the PS current was 9.83 at 3.55V applied for one hour . At the end of the hour, the Mm reading at the diagonal P and N terminals was 3.311.

The next day on Oct. 10, 2022 I performed the same thing to set 9-12 and 13-16. This time I realized I could use the PS's fine tune knob to adjust the current to 10A so both sets (individually) were charged at 10A at 3.55V for one hour. Each set had a Mm reading of 3.311V at the end of their hour.

They all responded almost identically. Each set charged to 3.311V except 1-4 which charged to 3.314V (multimeter reading) at the end of an hour. I left each set connected in parallel. I've since checked them regularly (once or twice per day). They have all settled from their initial charged reading. Now 6 and 5 days later they are resting at the following voltages and have been for the past three days. Set 1-4, 3.292V, Set 5-8, 3.292V, Set 9-12, 3.293V, and Set 13-16 3.294V

Are you planning to capacity test the cells as part of commissioning?
If you have the time it would be useful.
If you test them, then you can curate the packs by capacity.

The strongest cells in battery 1.
The second strongest cells in battery 2.
The third strongest cells in battery 3.
The weakest cells in battery 4.

Do you have a capacity tester?

So, rather than guess, I'll tell you, I'm not entirely sure what commissioning means in this case.
I don't have enough experience or knowledge to have thought about curating, but it makes perfect sense. Thank you.

I'm not sure I have a capacity tester. I have a multi-functional battery meter, model: PZEM-015 battery:0 ~ 200V current:0 ~ 300A. It comes with a shunt. I think it's what I see Will monitoring batteries with when he tests them using an inverter and hot air guns and such. The only inverter that I have is an older Xantrex Pro Sine 1000, a 1000W inverter.
 
The cells are basically pristine based on many I've seen in videos. No swelling and no dents. The sheet of black plastic on the top is not glued on well in some cases, but I'm not sure that indicates anything.
The black plastic has probably been applied by the reseller to obscure the original barcodes.
So, rather than guess, I'll tell you, I'm not entirely sure what commissioning means in this case.
Commissioning means all the preparation to make a battery and get it ready to be put into service.
I don't have enough experience or knowledge to have thought about curating, but it makes perfect sense. Thank you.
Curating in this case just means sorting by capacity.
I'm not sure I have a capacity tester. I have a multi-functional battery meter, model: PZEM-015 battery:0 ~ 200V current:0 ~ 300A. It comes with a shunt. I think it's what I see Will monitoring batteries with when he tests them using an inverter and hot air guns and such. The only inverter that I have is an older Xantrex Pro Sine 1000, a 1000W inverter.
I suggest to charge and discharge and re-charge the cells individually before you assemble them into packs.
I have this capacity tester
Its not the most accurate but it will give you a method to determine the relative capacity.
 
The black plastic has probably been applied by the reseller to obscure the original barcodes.

Very possible. They have barcode stickers on the positive sides. They each have a unique serial number. The serial numbers were not used on the supposed Inspection Report that was sent with the cells. Just numbers 1 through 16 which were not on the cells. For that reason I didn't find the sheet very useful. Of it's indeed even factual. I'm attaching some battery pics and a pic of the Inspection Report sheet. It has my notes from Oct. 9 of this year. I labeled the cells 1 through 16. They are not correlated to the numbers on the Inspection Report sheet other than by happenstance.

1665884932252373573926945759143.jpg16658850302212700274134979549301.jpg16658858292013204577502998046683.jpg16658873387792625660947779338127.jpg

Commissioning means all the preparation to make a battery and get it ready to be put into service.

Got it.

Curating in this case just means sorting by capacity.

Understood.

I suggest to charge and discharge and re-charge the cells individually before you assemble them into packs.
I have this capacity tester
Its not the most accurate but it will give you a method to determine the relative capacity.

Duh, Turns out I have one and have just been waiting to learn how to use it. I think I bought it about the same time I ordered my batteries. I'd appreciate if you could take me through the steps you mentioned above. I'm a willing student.

16658851120458719153532418965005.jpg
 
I think I bought it about the same time I ordered my batteries.
Nice.
I'd appreciate if you could take me through the steps you mentioned above. I'm a willing student.
Sure.

Have you made quality 10 awg leads for your bench psu?
Should be ring terminals on both ends and 10 awg wire.

Step 1. make some 10 awg leads for the capacity tester.
Put ring 1/4"(6mm) terminals on the battery side and probably #10 on the capacity tester side.
The crimp colour code is yellow for 12 to 10 awg.
I like Gardner bender, they are available online and at the big orange store.
Do you have a crimper?

Step 1. learn how to use the capacity tester.
You want low voltage disconnect set to 2.5 volts
The battery voltage won't actually get to 2.5 volts but we don't care as long as what we do is consistent across all cells.
I don't have a power supply or cell to figure out how to use mine so I hope you can do that part yourself.
If not I will have to whip something up.

The most current you should pull through the tester and leads is 20 amps.
20 amps @ 3.65 volts = 73 watts
20 amps @ 2.5 volts = 50 watts
In order to dissipate that heat you need the power brick attached to make sure the fan runs.
Even if the fan can run off the device under test we don't want to do that in case it messes with the results.

Step 2. Charge the cell full to 3.65 volts @ 10 amps using the bench psu.
Terminate the charge when the tail current is less than 1 amp.
Don't leave the charger connected for too long.
Less than a day would be acceptable.
Less than an hour would be excellent.

Step 3. Zero the amp hours and watt hours counters on the capicity tester.
Discharge the cell until it disconnects at what it thinks is 2.5 volts.
The cell won't actually get to 2.5 volts but that is fine.
Record the results.

Step 4. Recharge the cell to 3.0 volts @ 10 amps use the bench psu.
You can stop when the current drops to less than 3 amps.

Step 5. Move to the next cell and repeat the process starting at step 2.

@sunshine_eggo if you see a hitch in my process please tag in.
 
Actually lets discharge at 14 amps.
That way a discharge from full should take ~20 hours and you won't be pushing the cheap little device to the max.
 
Have you made quality 10 awg leads for your bench psu?
Should be ring terminals on both ends and 10 awg wire.

Step 1. make some 10 awg leads for the capacity tester.
Put ring 1/4"(6mm) terminals on the battery side and probably #10 on the capacity tester side.
The crimp colour code is yellow for 12 to 10 awg.
I like Gardner bender, they are available online and at the big orange store.
Do you have a crimper?

Thanks for all of this.
Sorry it's taken so long to reply. Really busy the past couple of days. Our 36 wedding anniversary is on the 18th. We leave tomorrow for a trip to a cabin in the Blue Ridge mountains. We'll be back home in Thursday.

I have everything I need to make the leads, 10awg, ring connectors, crimpers, etc. I normally make mine about a meter long. Is that about right or do you recommend a different length.

Step 1. learn how to use the capacity tester.
You want low voltage disconnect set to 2.5 volts
The battery voltage won't actually get to 2.5 volts but we don't care as long as what we do is consistent across all cells.
I don't have a power supply or cell to figure out how to use mine so I hope you can do that part yourself.
If not I will have to whip something up.

The most current you should pull through the tester and leads is 20 amps.
20 amps @ 3.65 volts = 73 watts
20 amps @ 2.5 volts = 50 watts
In order to dissipate that heat you need the power brick attached to make sure the fan runs.
Even if the fan can run off the device under test we don't want to do that in case it messes with the results.

Actually lets discharge at 14 amps.✔️
That way a discharge from full should take ~20 hours and you won't be pushing the cheap little device to the max.

I understand your directions. One cell at a time. Limit current to 14mps, maximum = 14A at 3.65V = 51.1W, cut off = 14A at 2.5V = 35W.
Will P actually made a video about using one and I'm pretty sure I've seen at least one other. I'll look to research those. Plus, I have the directions.?
If I get stuck, you can help me noodle through it.
You mention the battery will not actually get down to 2.5V how do we know this?

Step 2. Charge the cell full to 3.65 volts @ 10 amps using the bench psu.
Terminate the charge when the tail current is less than 1 amp.
Don't leave the charger connected for too long.
Less than a day would be acceptable.
Less than an hour would be excellent.

Got it, I should be able to monitor this pretty closely.

Step 3. Zero the amp hours and watt hours counters on the capicity tester.
Discharge the cell until it disconnects at what it thinks is 2.5 volts.
The cell won't actually get to 2.5 volts but that is fine.
Record the results.

This will probably become obvious when I'm doing it, but what results do you mean?
Step 4. Recharge the cell to 3.0 volts @ 10 amps use the bench psu.
You can stop when the current drops to less than 3 amps.

Understood.

Step 5. Move to the next cell and repeat the process starting at step 2.

Understood
 
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This will probably become obvious when I'm doing it, but what results do you mean?
Amp hours and if available watt hours.
The idea is to sort the cells by capacity so that we can make capacity matched batteries.
 
Amp hours and if available watt hours.
The idea is to sort the cells by capacity so that we can make capacity matched batteries.
Check.
We're relaxing in the cabin we rented. I'll try and do some reading on the Capacity Tester over the next few days. We head back home on Thursday.
 
Hi John,

I owe you an apology. As you may remember, the wife and I went on a trip to mountains two weeks ago to celebrate our anniversary. I intended to get up with you as soon as we returned, but some materials to build a couple of dressers (I'd promised my wife) arrived while I was gone and I got caught up in that upon our return. I kept telling myself I needed to let you know what was happening and kept forgetting to do so. Anyway, I'm expecting to be at this for at least another week and then if you are able and willing, I'll get back up with you to continue the capacity testing and cell sorting. I did watch some videos while we were gone and I think I have a grasp on what to do. I will post as soon as I begin testing. At this point I just wanted to offer my apology for what was definitely a lapse of good manners. I'm very, very grateful for the time and mentoring you provided me with.

Respectfully,

Pete
 
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