Charge as cell or pack

CBlack

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May 14, 2018
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Thanks for reading and providing feedback on this. I have learned a lot but finally at a very long road on a project that got delayed by a year.

So I have a couple hundred 18650 that i am looking to make a 24v 7S. I am shooting for around a 28P but i am almost done with testing the batteries so that go up or down when i get them all changed.
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UPDATE. Broke down the cells from laptops and other packs to individuals cells. I then charged them up to 4.1 to 4.19 and noted it on each cell. I put them into storage to let them set but didnt get a chance to get back to them until about a week ago. I went back and check to make sure they were holding pretty close to the noted voltage and separated all that was not. I set up the capacity checking station, i have about 18 cells testing during the day. So at the point, most of them are capacity checked and documented on the cell. I also put them into different boxes, 500 to 1500, 1600 to 1900 and 2000+ . My way of testing is at 1 amp and I round down to the lowest whole number. example would be 2001 to 2099 would be listed at 2000.

I was going to start charging after i get everything tested, easier for me to do the one stage to the next at a time to keep from getting interrupted and loosing track. I have about a day left and then i can start the charging but wanted to know if it was better to charge on the pack level, cell back to a pack or done at the one on one level. I was going to use the tp4056 and the tester I have to charge the cells at a slow rate vs just pushing them hard. I have a LiitoKala Lii-500, 5 imax b6 and hand full of tp4056 to get them back up and going to back to correct voltage for use/building.
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Main point that I have not been able to (funny err opps) fully understand or need help with is, to charge the cells or packs.

My educated guess is to charge in cells so that you can identify any problem cells and help eliminate anyone that could be labeled a burner.

Any feedback or good reference point of reading/watching, is greatly appreciated. If I have left something out that should be needed to help with making a recommendation, please say so I will try my best to answer any question I can to help.


CB

Goal of having some on-grid living with the working to being self reliant.... =P
 
In one part of your post you say you are almost done testing your batteries and in another you are asking if you charge cells or packs, so I dont fully understand where you are at in the process for your question.

Assuming you haven't started testing, you should test individual cells. Especially since you dont really have that many cells. A lot of times cells in parallel will have 1 CID cell and another active cell, but you can't know that unless you break packs down to individual cells. Also, besides CID, some cells may have manufacturing defects that prevent the cell from holding any charge. I dont have an exact percentage because I didn't catalogue every cell I tested, but it happened often enough that I decided testing individual cells made more sense than whole packs or even cells in parallel.

On the other hand, if you are talking about the packs you assemble, then yes, you do charge the packs. It would be very difficult to charge on the cell level. You just hope that your testing was thorough enough that you weeded out the bad cells.
 
Dallski said:
In one part of your post you say you are almost done testing your batteries and in another you are asking if you charge cells or packs, so I dont fully understand where you are at in the process for your question.

Assuming you haven't started testing, you should test individual cells. Especially since you dont really have that many cells. A lot of times cells in parallel will have 1 CID cell and another active cell, but you can't know that unless you break packs down to individual cells. Also, besides CID, some cells may have manufacturing defects that prevent the cell from holding any charge. I dont have an exact percentage because I didn't catalogue every cell I tested, but it happened often enough that I decided testing individual cells made more sense than whole packs or even cells in parallel.

On the other hand, if you are talking about the packs you assemble, then yes, you do charge the packs. It would be very difficult to charge on the cell level. You just hope that your testing was thorough enough that you weeded out the bad cells.

Dallski, I have updated.

Editing to say thank you, I got some sleep and this makes more sense.
 
Assemble your packs and then charge the whole pack up. This allows you to push a much higher amp and use a better charger than the TP units.

Going to assume you did a discharge capacity test and the cells are down to around 2.8-3V. So it'll be easier and safer to assemble them at this time. Otherwise, fully charged cells need to be no more than about .1-.2V difference as connecting could cause the fuse to pop or the wire connection to get hot during assembly.
 
Korishan said:
Assemble your packs and then charge the whole pack up. This allows you to push a much higher amp and use a better charger than the TP units.

Going to assume you did a discharge capacity test and the cells are down to around 2.8-3V. So it'll be easier and safer to assemble them at this time. Otherwise, fully charged cells need to be no more than about .1-.2V difference as connecting could cause the fuse to pop or the wire connection to get hot during assembly.

Yes, this is the current state I am at. Thank you, this makes it easier. The nice charger did do charge cycle at the end so I will have to find them. I will rig up some quick way of finding the voltage to make sure.
CB
 
Ok I read your updated post. Yes, as soon as you are done capacity testing your cells, you can start assembling your packs. No need to wait for a self discharge test, as you inadvertantly did that over the past year :) Since you say your tester charged the cells after testing them, they should all be fully charged. Like Korishan said, check voltages so there is not too much of a variance before putting the cells in parallel.
 
Dallski said:
Ok I read your updated post. Yes, as soon as you are done capacity testing your cells, you can start assembling your packs. No need to wait for a self discharge test, as you inadvertantly did that over the past year :) Since you say your tester charged the cells after testing them, they should all be fully charged. Like Korishan said, check voltages so there is not too much of a variance before putting the cells in parallel.

I broke the original packs and let them set to check for the self discharge. I missed this set up on the last set of batteries so they are not really "known" lesson learned so that asking questions to make sure. thanks again Dallski for taking time to help a noobie out.

CB
 
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