electric unicycle battery specs?

[jimmyhackers]

i have two electric unicycle batteries....they are 2ah 16s lipo/li-ion. they came from two cheapy chinese 300w unicycles.

so max amp draw from them should be 300w/67.2v = 4.5ish amps. in their original designation

i noticed in a few cells were not balanced properly in one.....after manually/singularily charging them upto balance.....they have stayed reasonably well in voltage range with each other after a few cycles.

they come with an integral bms board. Does anyone know anything more about these kind of boards/cells?.
like max amp draw, do the bms boards have a max cut off amperage, how well (by what means) do they balance? etc etc.

I ask as i use them as a backup/emergency battery for my other ebikes, rated at 1000w and 1500w so like 13-21amps :s.
i wonder if i would be better of combining the two into one to reduce the currentdraw/stress on the cells?

any help would be appreciated.

thanks in advance
jim

 

[fechter]

If you post a good picture of the BMS board, we can probably figure out some of your questions.

 

[jimmyhackers]

i just took one apart today for some pics. couldnt see a serial number on the board



heres one of the cells serial number/data

 

[fechter]

I can see the BMS has a current measurement shunt, so most likely has a feature to trip if the current goes too high. It also looks like it has balancing, but hard to tell for sure as those parts are under the black stuff.

While you could possibly change the over current trip point, the cells themselves may overheat and burn at a higher rate.

You could parallel multiple packs to get a higher current.

 

[jimmyhackers]

yeah the cells look like low current draw like the PKCELLS i bought a while ago. 2C max discharge so 4amps max draw. this would be inline with the 300w(4.5ish amps draw) initial intention for the packs

yeah im not sure on the balancing......wether it actively balances throughout the charge or just waits till the cell gets to 4.15V (ish) and burns off the extra charge as heat.

i noticed when i first got it, the cells that were charged/in balance were at/around 4.2v or slightly higher. the charger itself had the green light on indicating it was full/happy.

now they are all resonable back in balance they only get to 4.15ish Volts a cells

this makes me think the BMS board only burns off extra current around 4.2vs to balance and the charger turns off when it sees the 67.2v or just under.

i think i am best in just combining the two for double current draw.....8amps max.