"Emergency" battery charge?

[Tilmann]

Dear battery experts out there, I need your advice please:

I have a new Gotway Mten with a low battery and I can't charge it anymore (likely due to a broken BMS).

The picture shows the voltage on the main battery connector to the motherboard. Connecting the charger to the separate charging connector does not do anything good (no current flow).

As things are progressing (slooooow), resolving the problem may take a while. Now I am afraid, that storing the battery at this low charge for any extended period may harm the cells.

Question: Can I charge it up to a good level for storing (like between 60V and 62V) by connecting the charger directly to the motherboard connector??? This connector seems to work as the Mten still functions with the battery installed. I'm aware, that screwing up polarity or overcharging it may cause some spectacular fireworks and that there will likely be no balancing with the broken BMS. So, I would carefully babysit it while charging and disconnect at reaching about 61V.

Do you think, that's a good idea?

[Gimlet]

At present you are at just under 57V, there's no reason to worry until it aproaches 50v so I would just keep an eye on it as apparently they're better stored at medium charge than fully charged.

[Tilmann]

Thanks much @Gimlet!

[esaj]

The critical voltage is around 2.5V per cell, so for 16S pack that's 40V, so no panic yet. Actually 56.9V is probably better for storing than near 60V or over.

As for charging it with the wheel mainboard, I'm not sure what you mean. Does the wheel power itself from the charger and then charge the battery through the discharge wires? From what I've understood, charging it over the discharge wires shouldn't be a problem (that's what the wheel does during regenerative braking), as long as you can somehow control the charging voltage and current.

Edit: 1000th post   

[Tilmann]

The critical voltage is around 2.5V per cell, so for 16S pack that's 40V, so no panic yet. Actually 56.9V is probably better for storing than near 60V or over.

As for charging it with the wheel mainboard, I'm not sure what you mean. Does the wheel power itself from the charger and then charge the battery through the discharge wires? From what I've understood, charging it over the discharge wires shouldn't be a problem (that's what the wheel does during regenerative braking), as long as you can somehow control the charging voltage and current.

Thank you, too, @esaj! I was afraid, the present 56.9 is pretty low since the Mten indicator is down to one led (from 6). So I am relieved to learn, the voltage is well within safe storage range.

Sorry for being a bit unclear about my ideas:

The battery has 2 connections: the metal plug for charging, the yellow XT60 to the motherboard. Connecting the charger to the metal plug just pulls up the voltage to 68V, but no charge current flows. So, ingenious me went to the next electronics store (on the Msuper, of course ) and bought some high current wires and a male XT60. If I cannibalize the remains of my blown up Charge Doctor for that 3-pin metal plug thing (whatever its called - the electronics shop didn't have it anyway), I can solder a makeshift "emergency" charge adaptor.

As I learned from the advice, that I can safely wait for as long as 6.9V (or 16.9V) self discharge may take, the parts go in the drawer and I focus on resolving the BMS problem... 

EDIT: Uuuuh, and congrats to your 1000th post, @esaj!!! You're awesome!