replace 12V 17Ah battery in jump starter

[openspaceman]

I have been given an old car jump starter pack with an inverter and tyre pump, the gel cell 17Ah battery is defunct.

I also have an 80V 4Ah battery from a mower that is beyond repair as the control board is defunct.

Assuming the battery consists of standard Lion cells I should be able to construct a battery with 5 cells in series adding cells in parallel to add capacity.

Where can I find a BMS that can prevent over discharge, keep cells balanced and prevent overcharging?

[Stinsy]

“12V” li-ion batteries tend to be 4s. Loads of these on the usual places to get Chinese stuff. Just make sure the BMS is rated for the current or use a small one with a relay.

[openspaceman]

Thanks.

If I use a 40A 4S one for things other than jump starting would it be possible to bypass it for jump starting or should I just use it as a power pack?

[Stinsy]

Thanks.

If I use a 40A 4S one for things other than jump starting would it be possible to bypass it for jump starting or should I just use it as a power pack?

You can do whatever you like! You can have the electric going through the BMS for normal power pack operation or access the terminals directly for use as a jump starter.