What is the smallest battery I can use

[Brannenthompson1]

Hi, The BMS has got a gremlin in my battery and I've ordered a new one BMS that is until then I have a spare 30 18650's all 2000mah can I make a small 36 v pack to use until by proper battery arrives? I don't want to strip the bottle battery, So I'm running 22amp controller and a 500w motor, yes I know amps x volts is more than 500w, obviously, the 30 cells are not going to push out 22 amps but will it work and be safe, Thanks love the whole E-Bike community. Sorry to ask but I'm on a steep learning curve and getting older I can keep cycling which I love I even ride to work in the wet and cold as I live in North Devon so if it's just me I use my bike. Anyone got any tips on getting the better half to buy and ride a tandem an electric tandem would be amazing.

 

[anotherkiwi]

Hi, The BMS has got a gremlin in my battery and I've ordered a new one BMS that is until then I have a spare 30 18650's all 2000mah can I make a small 36 v pack to use until by proper battery arrives? I don't want to strip the bottle battery, So I'm running 22amp controller and a 500w motor, yes I know amps x volts is more than 500w, obviously, the 30 cells are not going to push out 22 amps but will it work and be safe, Thanks love the whole E-Bike community. Sorry to ask but I'm on a steep learning curve and getting older I can keep cycling which I love I even ride to work in the wet and cold as I live in North Devon so if it's just me I use my bike. Anyone got any tips on getting the better half to buy and ride a tandem an electric tandem would be amazing.

What cells are they? The important thing when making a 3P10S battery is the Amp output of each cell. You won't want to draw too much current to prevent the battery from heating too much.

 

[Nealh]

If they are old 2000mah lap top cells then they will be very crap and won't handle much draw, it depends on the cell in use. Voltage sag will be terrible.

 

[Deleted member 4366]

It's not going to work at 22 amps. That was probably too much for it when you had 40 cells, which might be the reason for your present problems. If you have some way of cutting the power right down, you might get something out of it.

If you want to run with 22 amps, you need to bite the bullet and get a decent battery with proper high-discharge cells, like Samsung 30Q.