How to turn two small batteries into one big? (BMS related question)

[crazymaster]

Hello!

I bought 3 of these batteries:
https://www.ebay.com/itm/382426943503?ul_noapp=true

and i have the battery of my bicycle which is broken(it was 24V 8.8ah):








This is the BMS:

I

The battery contains 7 battery packs of 4 batteries each.

As we see from the photo only B1,2,3,4,8,9,10 are connected.
What happen if i remove all cells(which are completely broken, and add the cells of the chinese battery i bought? If i add all from B0 to B10 i should get 36V right?



If that is not going to work can i just use the cells of 2 chinese batteries and connect them to one of the chinese BMS? Or it will not work correctly?
I just want to save some space and if possible to not use both of bms for the modified battery...

In last case if this kind of modification is not good. I believe that it should be ok if i just connect 2 of the chinese batteries in parralel to get 36V 8.8Ah?




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And one another question...

I bought this battery - 24V 15AH:

http://vi.vipr.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=162884470882&t=1522916465000&tid=310&category=177814&seller=petrolscooter&excSoj=1&excTrk=1&lsite=3&ittenable=false&domain=ebay.co.uk&descgauge=1&cspheader=1&oneClk=1&secureDesc=0

I am satisfied and the price is very good - just 115pounds...

The questions here are:

1. Is it possile to make it 36V 15AH with the original BMS, or i need to change it with new from ebay?
2. Is it possible to mix the batteries from the 4.4ah chinese model stated above to make it 36V or i need to buy one more of the same bottle type battery? Is it possible to add more than 4 in pack?

 

[Deleted member 4366]

You need all the same type cells in a battery. Don't mix them.

 

[crazymaster]

what about the 36v 4.4 chinece cells ?
can i use one of their bms for 2 batteries or i need just to fit 2 batteries with their bms in my plastic box?

what about my original 24v 8.8ah bms? can i use it for the cells of the 36v battery ro make one big 36v 8.8ah?

 

[Deleted member 4366]

You can use all three cell-packs with one BMS as long as the BMS can provide the current that your controller allows. You'd need to parallel all the balance wires and the two main power wires from the cell-pack.

 

[crazymaster]

yes but how i can understand if the chinese bms have the needed current and what about the bms from my 24v battery? can i use it? it also have lights showing the battery level are they going to self adjust for the 36v battery or no?

 

[Deleted member 4366]

24v LEDs will be wrong for 36v. There's no way to say whether that BMS will work at 36v. Often they use the same PCB and connectors, but have different components on the PCB.

 

[crazymaster]

i see... i was thinking that they are ready to increase the voltage with just connecting more batteries to the free B1-9 holes.

What about converting the 36v battery into 12v(or around)?
i think about making it from 36 to 13, so i can connect later to my 24v battery in series to 36v from it?

 

[Deleted member 4366]

I would put the three 36v batteries in parallel and get a 36v controller. that will make your bike go much better than 24v. make a 3 into 1 harness for the power leads. the only problem is that you have to disconnect all the batteries from each other while charging, and you'd have to charge them one at a time.

Alternatively, you could try paralleling the cell-packs to one BMS. It'll probably be OK because hover-boards use similar currents to e-bikes. My guess is that the BMS is 15 or 20 amps, which are both enough.

 

[crazymaster]

I finish with putting the batteries in my old case. I have tested it and it worked nice a few minutes. Tomorrow i will make full day test.

I just used the 3 batteries and connected them in series... in stock format with both BMS.

Why you say that i need to disconnect them when charging?
As they have their own bms, maybe they should work fine?

 

[Deleted member 4366]

You must only connect them in parallel when they're at approximately the same voltage as each other, otherwise you'll see some smoke.

You must separate them for charging because if you leave them connected, charging one will charge the other two through their discharge wires, which will bypass the charge safety controls in the BMS. I.e. any single cell can be pushed over its maximum, which would cause it to explode. The whole battery would then turn into an incendiary device.

 

[crazymaster]

i already finished one full charge and one discharge (25 miles range)
i am going to make a new charge in one hour....

can i try to use like that a few days or i should stop asap and buy 36v Bms and to connect in the right way?

 

[Deleted member 4366]

I already said, connect all three cell-packs to one of the BMSs. It'll probably work OK like that. Just parallel the ribbon cables and the positive and negative from each cell pack.

 

[crazymaster]

Today i just received this charger:
https://www.ebay.co.uk/itm/163010952787?ViewItem=&item=163010952787


My battery(2 parralel packs of 4.4ah, so total 8.8ah, currently with 2 BMS) was charged up to 40.5V with another charger(i am using 48V chargerr and i put this battery + 12V battery to be able to charge)
and i just plugged the new charger to complete the charge. It worked fine around 20 mins, then i just decided to take a look if the fan of the charger works, and when i moved it with fan facing up... it blown...

What may be the reason? No fuse blown, just i noticed 2 resistors around the 220V voltage circuit:
https://scontent-lhr3-1.xx.fbcdn.net/v/t34.18173-12/30776252_1975203005847590_1660102715_n.jpg?_nc_cat=0&oh=1af4b5d5a184fd25768771ebfa46e9a0&oe=5ADFD07E


Is the problem in the charger, or it blown because of the battery?
The battery is working fine.



Tomorrow i am going to buy this battery:
https://www.ebay.co.uk/itm/382419502129?_trksid=p2047675.m570.l6349&_trkparms=gh1g=I382419502129.N105.S2.R3.TR4&autorefresh=true


And i wonder if i can use 5A charger on it without problems?
This one for example: https://i.ebayimg.com/images/g/FVkAAOSw2k9Zd80h/s-l1600.jpg

Is it ok to use it on the 8,8ah battery too?

 

[Deleted member 4366]

It's best to charge with the lowest current that's convenient, which is normally around 2 amps. The higher you go, the faster you'll wear out the battery and the more chance of running into problems. 5A will be the maximum that the charge mosfet in the BMS can take.

 

[crazymaster]

For which battery you talk about?
And about the blown charger... what may be the reason?