Does 14s bms have low voltage protection?
Tacking on to this question, I have a 14s 4p pack with the correct BMS (from here). Batteries are Samsung INR18650-30Q (15A 3000mAh)
Currently, fully charged on the pack is showing about 57.7, which seems a bit lower than charts I have seen with voltage vs % remaining.
The BMS is cutting out (low voltage, I assume) around 46v, which, according to the same chart, is ~30% left.
Anyone have thoughts on whether this is an accurate cutout for this package, whether my BMS is off, or i have some cells that are degraded and causing the whole thing to cut out early?
Appreciate any feedback. The bike has been a blast, FYI.
Hey John, sounds like two different things here that might be connected. For the full charge stopping at 57.7V, that's likely a balance issue where not all cells are balanced. It's cutting off charging when the first cells reach full, but the lower cells don't have as high of voltage, and thus the total pack voltage isn't 100% (58.8V for a 14s battery). It could solve itself if you leave it on the charger for a while, but a good method to check would be to measure the voltage of each parallel group if you can still access them. One or more much lower voltage groups might need manual balancing (charge them up with a single cell charger) to get them closer to 4.2 and help the BMS with an easier job.
The cutoff on discharge is likely from voltage sag. What is your discharge current, and are you using a V1.5 or V2 kit? The V1.5 is more prone to voltage sag as the kit is rated for lower current due to its higher resistance than the V2. However, if there is a balance issue then the lowest cell group could be causing a premature cutoff when it dips to the low voltage cutoff before the other cell groups.