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Newbe need alot of help
#1
Hi guys
i have 2 identical 24v 11ah battery which i want to convert into a 36v battery. i have a spot welder but need advice to put it together and what bms i need.
if some have drawings and can help me.
and what kind of charger do I need from aliexpress to measure the capacity of the cells
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#2
1) read the forum threads
2) more information is needed
3) 24V to 36V??? why?
4) why so large of a font? On my 50" monitor that text is huge!
5) this thread could of easily been put in Battery Builds section and not eBike territory. I state this because not everyone reads the eBike section as this is generally for the project builds of those types, not usually used for asking generic questions.
6) please read the FAQ section for more information
Proceed with caution. Knowledge is Power! Literally! Cool 
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#3
i usede googel  translate .for the rigth spelling ... maybe thats why letters got bigger .... it is a ebike battery that i like to convert from 24v to a 36v  becours my bike is a 36v and i got 2 * 24v batterys for free.... that is why i like to convert them
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#4
People often use the Opus BT-C3100 to test cell capacity.
In a pack you can only test one cell group at a time.
If you try to test more it will short circuit.

To change the battery config, you need to:
- open the battery carefully
- don't short circuit anything
- count how many cells total
- look to find how many cells in parallel, eg 2 or 3 or maybe 4 or more in groups.

Take pictures & post here, tell us what you find.

A 24V pack probably has 7 groups of cells, eg it is a 7s(unknown)p pack

You may be able to divide 1 24V pack into sections carefully.
Separate 24V pack into one 3s & one 4s group
Add 3s in series with the other pack eg
So total result might be 7s + 3s = approx 36V pack

You need a BMS for total pack. Original 7s BMS would not work, need new one.

You have to make new case for new battery (maybe two parts is OK).
Bike use gets lots of shaking vibration & needs waterproofing
Running off solar, DIY & electronics fan :-)
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#5
Other options.... just use the 2 x 24V packs and a 1800W boost converter from Aliexpress. Depends on how many amps the 36V motor needs. Or.... use the 2 x 24V packs as a 48V pack and a step down buck to 36V.

If you have an existing 36V battery and just adding more range then the amp requirement from the boost / buck can be reduced. Use the buck / boost to then re-charge / supply alongside the main 36V pack.
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#6
Or maybe use the two 24V packs in series like completelycharged suggests but limit the throttle value on a 48V controller to say 3/4 so the PWM control averages to 36V max to the motor.
Some people do deliberately over-volt motors but your life might be more exciting (& shorter) as a result!
Running off solar, DIY & electronics fan :-)
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