Ok so I have a 12s4p Tb battery and for some reason the range has drastically decreased. It continually cuts off and I can’t figure out what to do.
Yesterday I went for a long ride and it cut off at 7-8 miles and wouldn’t turn back on till I charged it a little. I was watching the vesc app on my iPhone and the cells were around 3.6-3.5 volts coasting while the entire voltage was 44v when the board dropped. I’ll post my ride settings and have my battery cut off start at 33.00 and the cut off end at 30.00. I normally do 36-33 but lowered it to do a long ride.
If you go down to 30V on 12s the cells are down to 2.5V. I would say that is too low for 30Q. At least you reduce the life time (number of charge cycles) a lot. I think you should stop between 36V and 39,6V - check the discharge curves of 30Q. Edit: typo
33.6V is down to 2.8V per cell on 12S (33.6v/12s). It should be Ok, but generally speaking going lower on minimum voltage and higher on maximum voltage reduces the number of charge cycles a battery can handle. Going down to 30V equals 2.5V per cell on a 12s - that is way too low if you care about battery lifespan. I have not had dead or weak batteries (yet!) so I do not know how they perform.
If you have a hobby charger… I normally unplug the balance lead from the bms… And measure the individual cells… Find the low one. Then use a 2 pin header to charge the low cells as 1s to bring it back into viable range.
This method only works if the cell hasn’t been abused… If you’ve done several charge cycles like this then likely the IR of that series pack is hgher and will likely no longer maintain balance due to the IR difference…
bad welds/poor connections within the P groups can do this. Its not the only cause of course. I’ve seen bad BMSs (the charge/discharge type. not charge only) do this as well when components start to go bad.
Battery and VESC should have a direct connection. BMS should not be included in that cycle. And then you can have a additional cycle between the BMS and the Battery. this way the BMS is only there for charging.