Is this a correct way to connect batteries together?

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Clarkdale44

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Hello,

I have four 18650's lying around, I thought I should use them to fix my old laptop battery.
I tested their capacity, two of them are at 1000 mAh and the other two are 2000 mAh each. Can I connect them together in the following way to get decent backup? Is the below method correct?



Regards!
 
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Clarkdale44 said:
Yes, laptop battery has it's own BMS board with connections for 0v,4v,8v,12v.
Click to expand...
Looks a pretty crazy idea - and a BMS is designed for identical batteries, not random collections of series and parallel ones, or even old and new identical ones.

If you've got 18650's that only test at 1000mAh, then they are well knackered.
 
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Nigel Goodwin said:
Looks a pretty crazy idea - and a BMS is designed for identical batteries, not random collections of series and parallel ones, or even old and new identical ones.

If you've got 18650's that only test at 1000mAh, then they are well knackered.
Click to expand...
I was watching a video that tested 10A 18650's as they appeared to be remarkable.. They were Chinese 1A (I think they claimed a 10A discharge current) but definitely not 10000mAh as described
 
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Yes, there are some fake 18650 batteries sold at AliExpress that are printed 30000mAh. You get 10 pieces for a few dollars.
A Lithium battery can easily produce its truthful mAh in 2 hours and maybe 30 times its mAh for a few minutes as in radio controlled models. My 280mAh Li-PO produces 6A when my model airplane is climbing vertically.
 
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Thanks for replies, I connected the battery in the above configuration with BMS board and it seems to work just fine. Wasn't sure it would work but since battery capacities are in balance, those two 1000mAh cells in parallel are equal to single 2000 mAh so pretty much it works.
I will replace all these with 3000 mAh in future to make a 6 cell battery.
 
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The issue isn't working 'once', it's how long it will carry on working.
 
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