makadam said:
I have a problem with e-bike battery 72v 20ah. Scooter has about 5000km, battery is 2 years old about 170 charging cycles.
<snip> Also charging indicator on scooter dashboard and battery itself is not accurate it show 50% when battery is empty (about 65V). Battery model is ZM11 LI-Ion with error diagnostic led. BMS model is BS01-B 181024 and motor is 3000W Bosch 72v.
Did the system ever work as you expect it to, or has it always worked the way it does now?
If full-charge voltage has dropped over time, or range has dropped, or performance, it's likely that cells in the pack have degraded or failed, and the BMS is trying to protect them from overcharge or overdischarge.
Do you ever see any of the error codes the label contains?
Battery voltage when is full charged is max 76.5V and only can be charged directly from battery connector( I need to remove battery from scooter and charge directly using battery C14 3pin charging port. When I try to charge from scooter plug (battery is connected with scooter with M25 plug 5pins), BMS stop working and I need to open battery to unplug 20pins connector (20s) and after some time to plug connector back. Using this method BMS is reset.
That usually indicates the BMS has detected a cell problem outside it's normal limitations, and has shut off the charge port to prevent cell damage that could lead to a fire. A well-designed BMS will do this, and will lock out charging (unless reset) so the battery won't catch fire from a damaged cell during charging, but cheap ones are hit-and-miss for this function.
Yours does do this, so it's probably just doing the job it's designed to do, and bypassing it this way may be dangerous.
Sometimes it just means the BMS has failed, but that's much rarer than cell failures.
Bypassing the charge port and charging thru the discharge port completely bypasses the BMS protection against cell damage and fires, and just exacerbates whatever problem the pack is having, potentially causing further damage to the cells.
I measure all single series and all of them have 3.82V when fully charged!
This is not very full for the typical Li-Ion cell. If the BMS is designed for long pack life it may be intentional, to not charge them fully, but the more common BMSs charge to 4.2v/cell.
Since we can't know for certain what the BMS is designed to do (no useful google hits on numbers from it), , we can make a guess based on charger voltage, and the 84v limit voltage on the case label, which matches the typical 72v battery of 20s, 84v fully charged, to 4.2v/cell.
What is the voltage the charger outputs when not connected to the pack?
If it doesn't output a voltage until it's connected to the pack, you'll need to put your leads on the charger output wires in a way that keeps them there even when not connected to the battery, but still allows you to connect it to the battery. Then do that, and then disconnect the charger from battery, watching the voltmeter display. It should rise to some voltage before shutting off, and that's the charger's actual output voltage, what it was intended to charge the battery to.
Knowing that, and guessing the 84v is what you *should* see, we can guess if it's a charger problem or a pack problem.