52v Vruzend Bsttery pack
Built a Vruzend battery from Samsung 3000mah cells from Ryobi power tool batteries. 13 x 8. All went well, all batteries had proper voltage, pack had 50+ charged volts. It replaced an original ebike battery that had lost it's ability to be charged fully. However when I ride the bike it seems to cause the controller to shut off while going up hills and comes back on again 4 seconds later. My original battery, even with it's reduced mileage production doesn't do that. Any suggestions what might cause this?
It sounds like the BMS is undergoing a protection cut out temporarily. It could be caused by a few different reasons, but the most likely culprit is that the voltage is sagging and tripping the low voltage cutoff. This can be caused by a few different reasons as well. A common one is current bottle necks, such as drawing the power at the + and - battery terminals from just one point instead of all of the cells at the + and - terminal of the battery. Another common one is using too few parallel cells meaning there isn't enough to support the current required.
Micah, I'm having this same issue. To fix that current bottleneck problem, would I just re-spotweld the whole battery? Like add extra welds all over each group? I'm working with a 14x4 pack.
If a current bottleneck from the connections is the issue, then yes that would help. But a current bottleneck could also be caused by the discharge wires only being connected to one cell in the first and last parallel group. Or the issue could be weak cells that have significant voltage sag (assuming you aren't working with brand new cells). So its not a guarantee that doubling up spot welded nickel will fix the problem, unless you know for sure that is where the problem is coming from.