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For my project I need voltage of 2 li-ion batteries in series. For charging them I would use this charger (one for each battery):

Could I connect those two chargers (with one battery on each charger) in series and plug them on 9/12V adapter? Or should I use 5V voltage regulator on each charger?

Another possibility would be to use 7.4V charger like this one.

I would use two identical batteries so I think batteries couldn't get unbalanced.

EDIT:

Could I use protection board in second link and a 8.4V adapter like this one?

Would 9V adapter be ok?

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  • \$\begingroup\$ Nobody's going to be able to tell without proper data on that charger. So a good recommendation would be : no datasheet, no sale. Consider using a charger designed for a 2S configuration, with charge balancing. \$\endgroup\$ – Brian Drummond Aug 17 '16 at 10:52
  • \$\begingroup\$ @BrianDrummond The second link contains a charger protection board for serial li-ion charging. Could I use this board and just plug 9V adapter to charge batteries? \$\endgroup\$ – user74857 Aug 17 '16 at 11:22
  • \$\begingroup\$ It wasn't there when I commented. \$\endgroup\$ – Brian Drummond Aug 17 '16 at 11:34
  • \$\begingroup\$ @BrianDrummond It wasnt, sorry. But would it work? \$\endgroup\$ – user74857 Aug 17 '16 at 11:38
  • \$\begingroup\$ It's not a charger. \$\endgroup\$ – Brian Drummond Aug 17 '16 at 11:38
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You cannot use 9V/12V and plug chargers in series. You need to use 5V and connect them in parallel.
Imagine that you connect them serially to 10V, and one of batteries is fully charged and the second one fully discharged. Then the first charger won't take any current and the second one will need 1A, it is not going to work, because the first charger will block current and almost whole 10V will be on this charger.

So you have to use that 5V regulator.

UPDATE:
Your second link is for 2 cells, so yes, that is better solution than 2 separate chargers.

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  • \$\begingroup\$ Thanks. What about 7.4V charger? I would use identical batteries. \$\endgroup\$ – user74857 Aug 17 '16 at 10:56
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    \$\begingroup\$ Is the item in second link even a charger? Or is it just a protection board? \$\endgroup\$ – user74857 Aug 17 '16 at 11:03
  • \$\begingroup\$ If the charger lacks a battery balancing feature, it will not be an optimal solution. Better find yourself a balancing charger if you want to charge lithium batteries in series. \$\endgroup\$ – Dampmaskin Aug 17 '16 at 11:05
  • \$\begingroup\$ So i couldnt just plug 9V adapter to that board to charge the battery? I think that the board itself has a balancing feauture \$\endgroup\$ – user74857 Aug 17 '16 at 11:12
  • \$\begingroup\$ Chargers for cells wired in series cannot be connected in parallel to the same power source. Fully isolated, independent power sources would be required, and even that is a dubious idea. \$\endgroup\$ – Chris Stratton Mar 10 at 22:12

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