I'm using a 14s1p 15ah headway battery pack to power my e-bike, which is peaking power of 3200w and 1500w continuous. The pack in configured as 2 rows stacked on top of each other, 7 cells in each row. So the neg and pos terminals are 2 cells next to each other on the front side on the battery pack, as the serial connection goes down the bottom row, flips up to the top row and go back down the top row to the front again where both terminals are. This battery is in a mostly air tight wooden box, ran without a bms but under close supervision (all cells are kept within a 0.005 tolerance).
The issue I'm having is 2 folds:
First, the the cells at the turn around point (i.e. the back of the pack physically, or the middle of the pack logically) are getting very hot, well over 100F, while the cells get cooler as I move to the front of the pack (the beginning and end of the pack logically), a few degrees cooler per cell to about 84F in the front. Does anyone have any ideas why this would happen (it's not just bad cells because I replaced the 4 hottest cells with new cells)?
Second, while riding a few days ago, it stopped completely providing current. I got home, and found the 4 cells I described above getting way too hot. The battery at this point refused to discharge or charge, even the next day after they cooled down. So I replaced these 4 hotter cells and sure enough, the battery now charges and discharges properly. However, these 4 cells that got very hot show a normal 3.23 voltage, the same as the rest of the pack at the time. How can the cells show a normal voltage, yet refuse to charge or discharge? (I'm assuming these cells went over the 149F max temp these cells are rated to, which caused this issue)
On top of that, I was running about 50 amps con on a long uphill for about 2 miles right before they broke. But depending on whose rating the cells, I've seen 75a con up to 150a con. Either way, I'm running them under even the lowest max con rating I've seen anywhere, so could something else be plaguing me? Again, can't be the bms, since there is none, and I used double connector plates between cells (all be it aluminum though) to decrease resistance in the connections.
Any help/advice is much appreciated. Thank you in advance!
The issue I'm having is 2 folds:
First, the the cells at the turn around point (i.e. the back of the pack physically, or the middle of the pack logically) are getting very hot, well over 100F, while the cells get cooler as I move to the front of the pack (the beginning and end of the pack logically), a few degrees cooler per cell to about 84F in the front. Does anyone have any ideas why this would happen (it's not just bad cells because I replaced the 4 hottest cells with new cells)?
Second, while riding a few days ago, it stopped completely providing current. I got home, and found the 4 cells I described above getting way too hot. The battery at this point refused to discharge or charge, even the next day after they cooled down. So I replaced these 4 hotter cells and sure enough, the battery now charges and discharges properly. However, these 4 cells that got very hot show a normal 3.23 voltage, the same as the rest of the pack at the time. How can the cells show a normal voltage, yet refuse to charge or discharge? (I'm assuming these cells went over the 149F max temp these cells are rated to, which caused this issue)
On top of that, I was running about 50 amps con on a long uphill for about 2 miles right before they broke. But depending on whose rating the cells, I've seen 75a con up to 150a con. Either way, I'm running them under even the lowest max con rating I've seen anywhere, so could something else be plaguing me? Again, can't be the bms, since there is none, and I used double connector plates between cells (all be it aluminum though) to decrease resistance in the connections.
Any help/advice is much appreciated. Thank you in advance!
