I was doing a system check this week and noticed my cells are preeeety tightly compressed in the NEMA steel enclosure I have them stored in. These are EVE 314 ah cells in a 48V pack assembled in two rows of 8. They have been in use for about 14 months now. Voltages on each cell match within 0.01V but I have one cell that tends to get out of balance occasionally (oddly it is one of the outer packs). I get the full expected kwh from these cells. I don't think I have a single swollen cell given the spot on voltages throughout all SOC and both rows of the pack are tight - not just one. Width wise there is a lot of space between the case wall and the cells.
When I assembled the pack, the cells were not charged fully (perhaps 40-50% maybe?) and there was probably a 1 or 2" inch gap on clearance on either row of the pack. I didn't have trouble dropping the cells in and getting the last one to fit in other words. I did initially check things once the cells were charged to make sure they are not too compressed and there was still a gap on either side of the two rows of cells - eg no compression. We all know cells expand with SOC so I dropped them down to about 40%/~52V and there was a small improvement in the amount of compression because I could (get ready for a gasp!) move the BMS wire that was pinched
between one cell and the enclosure wall. I thought I had these routed off to the side and zip tie secured but this one was apparently not! Thankfully that wire did not short to the outer casing and the cells did not pop off from over compression. The acrylic plates I have between cells are still very much not movable and if you hold a level to the outside of the box there is a clear deflection along the center midline of the box. I want to break the pack down, but I really don't think I can without getting out the hack saw. The cells I have not given a hard wiggling but given I cannot move the spacers I don't think they're going anywhere. The silver cap on top all appear to show a slight bulge and I don't see one cell that this silver cap looks particularly more "swollen". I feel like that bulge is not usually there at this pack voltage I'd also note. Multimeter isn't showing a short of pos or neg to the case but I have these fully surrounded by acrylic sheets anyways
Would you drop the pack voltage further to see if I can get a cell out (to 48V or lower?) or should I just cautiously saw the side of the case with the larger gap and trash the case? I am a bit leery to make a move given this case is not on casters and would prefer to not risk hitting a cell while sawing the case off. I'd use a hand saw for sure! I have already ordered a new case to replace this (the EEL case as it fits these larger cells). Definitely important to look over your system often!
When I assembled the pack, the cells were not charged fully (perhaps 40-50% maybe?) and there was probably a 1 or 2" inch gap on clearance on either row of the pack. I didn't have trouble dropping the cells in and getting the last one to fit in other words. I did initially check things once the cells were charged to make sure they are not too compressed and there was still a gap on either side of the two rows of cells - eg no compression. We all know cells expand with SOC so I dropped them down to about 40%/~52V and there was a small improvement in the amount of compression because I could (get ready for a gasp!) move the BMS wire that was pinched
between one cell and the enclosure wall. I thought I had these routed off to the side and zip tie secured but this one was apparently not! Thankfully that wire did not short to the outer casing and the cells did not pop off from over compression. The acrylic plates I have between cells are still very much not movable and if you hold a level to the outside of the box there is a clear deflection along the center midline of the box. I want to break the pack down, but I really don't think I can without getting out the hack saw. The cells I have not given a hard wiggling but given I cannot move the spacers I don't think they're going anywhere. The silver cap on top all appear to show a slight bulge and I don't see one cell that this silver cap looks particularly more "swollen". I feel like that bulge is not usually there at this pack voltage I'd also note. Multimeter isn't showing a short of pos or neg to the case but I have these fully surrounded by acrylic sheets anywaysWould you drop the pack voltage further to see if I can get a cell out (to 48V or lower?) or should I just cautiously saw the side of the case with the larger gap and trash the case? I am a bit leery to make a move given this case is not on casters and would prefer to not risk hitting a cell while sawing the case off. I'd use a hand saw for sure! I have already ordered a new case to replace this (the EEL case as it fits these larger cells). Definitely important to look over your system often!
