[remy_martian]

Yup.

Assuming those are lithium cells, that's not a "bit" low.

 

[dcbusman]

Yes lithium cells, can I charge that one cell somehow to bring it up to the same level as the rest

 

[floydr]

My 36v ebike cuts out as soon as I put any sort of load on it, if I take it super gentle it's barely rideable. It has a 10 cell pack and one cell is a bit lower voltage than the others, 3.1v compared to 3.9 for the rest. Would this be causing the BMS to throw a wobbly and cut out?

It probably drops below LVC when a load is placed on it, assuming a LVC of 2.8V when a load is placed on it.
DIY battery pack? What cells? How many Ah is the battery? what BMS? Sounds like a bad cell or a bad BMS
Typical 36V ebike battery = 10s4p, 18650 NMC 10-12Ah. Find out what caused the low cell in the first place then correct the problem.
later floyd

 

[dcbusman]

It's a Phylion battery, not sure ofAh, there's nothing on the cells or case, 10 prismatic cells in series, came with the Lazer Ebike.

 

[floydr]

Ok ebike prismatic cells much the same Ah in lower end batteries 10-15Ah, can be 30-40Ah in higher end batteries or higher. Need to find out what caused the low cell first. You might be lucky and charge up the 3.1V cell to 3.9V same as the rest of the cells And be able to use it till it starts to go out of balance again. You have a problem somewhere my guess is the BMS or the cell is going bad. Replacing the cell will be hard since you don't know who manufactored the cells or the capacity of the cells.
later floyd

 

[dcbusman]

If it turns out to be the BMS that's crook, can you point me in the right direction for a replacement, I don't seem to have much luck getting a quality one.....

 

[floydr]

I prefer smart BMS's, most are bluetooth enabled so can use a cell phone to check on the battery. How many watts is the motor on the ebike? watts/36 = amps x 2 needed for your ebike at a minimum to account for inrush current.
500/36 = 13.88A 30A bms minimum
1000/36 = 27.77A 60A BMS minimum
Ant, JBD, Daly are all big in Ebike community you might find better answers in Endless Sphere forum
Later floyd

 

[remy_martian]

If it turns out to be the BMS that's crook, can you point me in the right direction for a replacement, I don't seem to have much luck getting a quality one.....

Troubleshoot the problem first. Stuff's too expensive and labor intensive to throw guesses at it.