how to charge diy batteries in series,when in 1 pack

[roadrunner]

ok,lets say im building packs from 18650 cells,, so i reverse one to get 12 volts,now when i charge what happens to the 2 thats reversed,ill have a neg on the pos end, will this work, i see a lot of packs built in things like this, especially laptop batteries, and medical stuff

 

[Bud Martin]

ok,lets say im building packs from 18650 cells,, so i reverse one to get 12 volts,now when i charge what happens to the 2 thats reversed,ill have a neg on the pos end, will this work, i see a lot of packs built in things like this, especially laptop batteries, and medical stuff

Can you please clarify "so i reverse one to get 12 volts"?
So how many cells are connected in series to make this 12V battery pack?

 

[roadrunner]

Can you please clarify "so i reverse one to get 12 volts"?
So how many cells are connected in series to make this 12V battery pack?

well it doesnt matter but 4,1 gets reveresed,so 3neg, and then 1 positive, how do battery packs charge properly when the pos and neg are reversed on the same end to add voltage,when you look at some battery packs,both the pos and neg have a strap across them and spot welded to increase voltage

 

[TacomaJoe]

You can't reverse a cell in the series and have any success. You strap the pos to neg of the next cell to add the voltage. 4 cells in series make a 12V battery. You can also strap all the pos together and neg together on 4 cells but you end up more capacity but the voltage will be 3V. With 16 cells you can parallel them in blocks of 4, then series connect those blocks to make a 12V battery with 4 times the Ah of a single cell.

 

[Charleswgibbs]

well it doesnt matter but 4,1 gets reveresed,so 3neg, and then 1 positive, how do battery packs charge properly when the pos and neg are reversed on the same end to add voltage,when you look at some battery packs,both the pos and neg have a strap across them and spot welded to increase voltage

If you are putting four cells in series you would need to reverse two cells. If four 18650s are lined up next to each other, and the first has positive up, then the whole sequence for the top of the cells would be pos-neg-pos-neg.

There is no polarity issues with charging cells in series. The current flows from positive to negative, so having the positive of one cell connected to the negative of another doesn't present any issues. The current just flows from positive to negative.