Thank you, HRTKD. I did the top balance in another room and then took the cells apart to move them. I did not know about the bus bar allignment, but have corrected this now. I intend to compress them once I install a BMS. When I finally got up to 3.55, I figured that was close enough and stopped the top balance.
I did use a power supply and did the top balance in my office so I could monitor the process while power was on. They were never left unattended and I turned off the charger whenever I was not there. I kept it at about 8 amps (seems like voltage was always under 10) and did not overcharge them. Yes, I used a DMM and regularly checked the voltage on the individual cells. They were not like this when I got them, but were flat.I looked back and noticed you did not receive the cells in that condition.
Lishen 270ah-272ah cell group buy.
Right. And with the newer cells coming with laser welded studs there is zero connectivity with the cells threads if the cell has threads to begin with. Actually, the cells that my main supplier laser welds the studs to come with no threads, no hole. Just a round flat surface. They buy them...diysolarforum.com
I wonder what steps you took to parallel top balance? If you used a power supply and set the voltage of the power supply after connecting to the cells then you overcharged them. They look like they were overcharged. Did you verify the voltage at the terminals with a DMM? Did you verify the voltage of the power supply was correct? You need to bring the voltages of the cells down and see if they will deflate.
Voltage under 10? Or did you mean current?
Yup, and the gaps shown in the photos are bad IMO. My EVE cells don't expand nearly that much with a full SOC.
There are very extensive and comprehensive threads on cell compression / binding / box building on the forum. Have a read.
Gaffers tape will only put pressure on corners and not in middle where swelling occurs. As suggested, read other threads.
Can you put a link in, please?
That's impossible because there are many threads on this topic. Search the forum for compression and you will find various ways of compressing your cells.
For reference, here's my compression method, used on a 4S "12.8V" battery pack. I used springs, 1/4" threaded round bar, and thin steel plates at the two ends. Also note the use of thin plastic separator sheets between cells. Your 200Ah cells might need 5/16 threaded round bar (instead of my 1/4" size) and stronger springs - but can otherwise be similar. https://diysolarforum.com/attachments/homebuilt-120ah-number-one-jpg.48423/
That's a pretty cool setup. Where did you get the springs? How did you size them? Thanks!
I bought from https://www.thespringstore.com, which has great selection but a relatively high minimum order amount (in dollars). For 5/16 bar with washers, you can use an inner diameter of between .4" and around .5", that is your most limiting factor. Depending on whether you will use 4 or six sets of bars and springs, you will need a maximum compressed strength of 70-110 lbs (6 bars) or 110-150 lbs (4 bars). You don't want them to become fully compressed, because further cell "expansion" will no room left to expand, and the resulting pressure will be non-linear. You need to have beveled ends ground into the springs, so that they will lie flat against their washers.
Maybe I'm missing something but...why would I top balance 4 cells individually? Shouldn't I be top balancing all 4 cells in parallel then when 0 amps, build the pack in series?
