dlwest

I would partially agree with that. The controller can be limiting the phase current it drives the motor with. Most of the motor softwares available use torque control algorithm where torque is proportional to stator current. Hence, the maximum torque depends on maximum phase current defined by the controller. But the motor's inductance dictates how much current the winding can develop at a given input voltage. So, with a high inductance (high voltage) motor, the controller might never be able to reach its current limit if supplied from lower voltage.

Actually, even if the cells look to be out of balance with 0.1V difference, they still may have the same SoC because of steep V curve at low charge levels. I would be charging the whole string to see if the individual cell voltages will level up at above 3.3V.

I'd connect the bench supply to the whole string, with current limited to 100 mA. It will reach 32V in a few hours. After that, the BMS should be able to take charge in the normal way.

Looks good, where are you based? I'd come over to check it with an electronic load, cash on collection.

Actually, I have two Kalkhoff batteries successfully recovered exactly from that state. Both were forgotten in storage for some time until the BMS was no longer able to take charge. Recovered by trickle charging using a bench DC power supply. Don't know if any capacity was lost or not, but they still do few days of commuting between the charges.

... are exactly the main reason of the ongoing war in Ukraine. Some people call the opportunity of keeping bad guys' money "good investment climate"

Oh yes, please DM me!

Please check charger output voltage first: it must output 42V briefly when you pull down the "R" pin on the cradle with 10k. If no other load is connected, 42V will disappear and the charger will lit green.

Looking for an old Derby Cycle (Kalkhoff Agattu, Raleigh etc.) battery with 5-pin bottom connector noted as "-"+"C"D"R" and 4-pin XLR charge port. In any condition.

Out of curiosity, is the old battery still with you? I am looking for a donor to get BMS board from. Thank you!

Have you tried charging through the side port, or through the bottom pins using dock stand provided with some Kalkhoff bikes? Is your charger original, or an aftermarket one? Side port pin 1 is a signal wire for the BMS to indicate the charger is connected. Pin 1 goes to 0V inside the charger's plug. Side port pin 2 is a signal wire for the charger to indicate the load is there, it is pulled down with 10k on the battery side, right behind the socket. Side port pin 3 is 0V Side port pin 4 is +42V, CC/CV These old batteries don't use any RS or CAN communication and are controlled by pull-down signals enabling charge and discharge. I have two of them, the 11Ah that works as intended, the other is 15Ah quirky one: despite having all cells perfectly balanced down to 0,01V, it shows full charge (all 5x LEDs lit) at 37V and empty at 35V. As a result, it gets fully charged in just 15 minutes and indicates zero charge left after 7 miles (not cutting off though). But if I ignore the LEDs letting the battery sit on the dock until reaching 42V, it gives full 50 miles range until the motor cuts off at ~32V, even after 0% charge was indicated.

Oh, nice to know. Would they be able to help on the following? I have an Integrale battery which does not engage the main switch, for an unknown reason. All other functions, including the housekeeping 12V output, are present. When I bypass the output MOSFETs, the motor works just fine, just as from a bench supply. To me, it's likely the BQxxxx BMS controller IC went nuts. It's a shame to through away 60 cells which are just fine

Yes pretty much, I had a successful few miles test ride yesterday. Since the bike was down for a week anyway, decided to get the motor overhauled, cleaned, re-greased with belray waterproof grease and painted over. This appeared to be done just in time, as the ratchet and the crankshaft roller bearing inside the motor both were found dry and about to seize. The motor is from 2016 and had never been opened before.

Some more details:

So the root cause of the problem of the question mark being displayed instead of the charge level was the display not being able to communicate to the motor over the CAN bus. The culprits are below, the two small filter capacitors in the middle one of which gone short: The most tricky part was to desolder the connectors, as the caps sitting under them did not seem to be reachable. Replaced with 330 pF 0603 250V rated ones. The defect can be identified easily by probing the two middle pins of the 4-pin connector which are CANH,CANL bus pins, against the ground which is one of the side pins. Normally, the bus pins must show 136 ohms between them (2x 68R terminating resistors) and infinite to the ground. In my case, one of the lines was short to ground.