Accus Lion

[Jofaur86]

there are 25 elements of 2500 Mah, in series // which gives 36 volts at 15 A according to the label on the electronic module. Some display 3.8 volts, others 3.5 volts? I have no current means of charging? Attached photo of the electronics

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[Jofaur86]

Sorry, it seems that the first part is not displayed? it's a group of 25 Lion batteries, which I would like to transform into a 7.4 volt 5000 Mah type 2SP2 pack, and my question is: is it necessary to install a BMS system or will a balancing plug be enough? Thank you in advance for your opinions and advice.

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[Rad_Schuhart]

I made my 2S2P and only wired a balance plug, nothing else.

It works wonders.

[Jofaur86]

Hello Rad, thank you for the answer, don't dare ask again, I'll see if I do it by tin soldering or spot welding? Have a good weekend

[Rad_Schuhart]

I did it with a soldering iron. Try to do it as fast as possible.

[Jofaur86]

Yes, or will I keep a bit of the current link, and form a loop on a forest, slip the wire in and solder it?

[Ecam]

Yes, or will I keep a bit of the current link, and form a loop on a forest, slip the wire in and solder it?

That works very well and has minimal heat input to the cell. I try to give equal lengths to each end of the cell (cut the link in the center of the spot welded strap).

[Jofaur86]

Hello, and thank you for the advice, I will see? hope the elements are not stuck together? and then seems composed of several series / parallel blocks (total 36 volts for 17 Ah) have a good weekend

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[Ecam]

I hope the elements are not stuck together?

They likely are, some de-bonder might work, but could affect the cell's shrink tube. I've re-shrink tubed cells before or even some electrical tape wrap would fix things although not as tidy as shrink tube. Battery shrink wraps are available in many sizes. Individual cell and then even for your final outer wrap for the completed battery..

That is an unusual battery pack. It looks to me as some series and parallel things going on. I think the cells are 3.7 volts each, the way it looks to me is each of the "six packs" are 7.4v and 3x the amps and then depending on how the wires were routed upping the voltage each time.

For those following and are curious, a two battery example: Linking the negative ends and the also the positive sides give the same voltage but twice the amps. Putting one battery's positive to the other's negative the two batteries will now measure twice the volts but the same amps.

This is how typical 24v military vehicle charging/starting systems use two standard 12v batteries.

[Jofaur86]

yes, I'll see, it's an electric scooter pack, I have a few elements below 3.4 Volts, but many in 3.9... there was some bad DIY (welding) on ​​the part electronic, so I don't expect to get everything back? I also have the control system, photo attached

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