Charging 18650 pack in Paralel

[SASEASASINI]

First sory for some mistake in my writing my native language is not english

My idea of charging 18650 in series from diferent tools lamps in PARALEL etc

First normal i charging them with chinese Bms 3 4 5 S but after some time they failed so one night i come with a idea to charging them in PARALEL

For every 18650 cell you need a double switch 2 way like in the schematic below

Pozition 1 - All 18650 cell are in series to power what you want

Pozition 2 - all 18650 cell are in paralel 4.2 for easy charging

 

[OffGridInTheCity]

Sure, with proper switching you can switch them to be parallel and then to be in series - e.g. one or the other. One advantage would be balanced cells as part of the charge process. Of course cost of switches, and in particular.... the manual switching back/forth in-between charge and discharge cycles could be troublesome.

How do you plan to use this battery?

 

[Korishan]

oooph, this could lead to some explosive mistakes if not done exactly correctly 100% of the time.
Perhaps if this was done via an mcu and some beefy FETs, it could be done safely. I would actually use 2 FETs for each leg of a series connection. So that 1 FET enables series connection while energized, and the 2nd FET would enable parallel mode when energized. These FETs would be powered in opposing connections to make sure they don't ever get turned on at the same time. But for safety, if they are both de-energized, the cells are completely disconnected, both from series and from parallel connections.

 

[italianuser]

I like the idea a lot. I couldn't get to think about the schema when I first looked at it, too many things in my mind right now LOL.

Yes, done in safety, with an MCU comanding operations would be great

 

[Redpacket]

You could also check why they did not last in the 3s, 4s, 5s, etc setup.
3s, 4s, 5s, etc use is normal, so there must be a reason why they did not last.
Each cell in 3s, 4s, 5s, etc string should be similar mAhr capacity.
You should also have a suitable 3s, 4s, 5s, etc BMS unit to check them like you had. Sometimes the cheap BMS fail = cells fail soon too due to no balancing/protection.