Is it safe to charge IMR 26650s inside Mag in series?

[Rando]

Working on a SST-90 Mag with 2x26650 in series. Is there a way to safely charge them in the light without removing the cells? When I built a ROP years ago I installed a DC socket in the cap similar to this one to charge the NiMh pack. Is there a safe way to charge IMRs the same way?

 

[Quest4fire]

You can't treat your IMR 26650's the same as a NiMh pack, different chemistry. Parallel charge lithium ion cells within the range recommended by the manufacturer, but since their are only two cells, why not just charge them one at a time just to be safe.
What kind of charger are you using?

 

[fivemega]

Working on a SST-90 Mag with 2x26650 in series. Is there a way to safely charge them in the light without removing the cells? When I built a ROP years ago I installed a DC socket in the cap similar to this one to charge the NiMh pack. Is there a safe way to charge IMRs the same way?

In order to balance charge, you will need 2 charging ports isolated from body and each charging port connected to one IMR cell then charge each cell at 4.2 volt at a time.
Note:
1- Make sure charging port does not use M*g body as a ground. Run positive and negative wires from port #1 to cell #1 and port #2 to cell #2
2- Make sure fully recharge both batteries prior to use.

 

[Rando]

You can't treat your IMR 26650's the same as a NiMh pack, different chemistry. Parallel charge lithium ion cells within the range recommended by the manufacturer, but since their are only two cells, why not just charge them one at a time just to be safe.
What kind of charger are you using?

I didn't think I could charge them in series, but I wondered if anyone had worked out how to charge them individually without removing them. I'm replacing the switch with a push pot so I won't have the negative grounded to the body any more and I'll have to run a - wire to the tail spring. I thought if I could charge without removing the cells it would minimize the stress on this connection. I currently use a WF139 (will use magnetic leads for the 26650s) but I'm not opposed to buying a nicer charger if I can make this design work.

In order to balance charge, you will need 2 charging ports isolated from body and each charging port connected to one IMR cell then charge each cell at 4.2 volt at a time.
Note:
1- Make sure charging port does not use M*g body as a ground. Run positive and negative wires from port #1 to cell #1 and port #2 to cell #2
2- Make sure fully recharge both batteries prior to use.

That's not a bad idea. Thanks for the suggestion. Since they're in series, the connection for the top negative would end up being same as the connection for the positive on the bottom, right? That means no charging both at the same time unless I missed something... ?

 

[fivemega]

Since they're in series, the connection for the top negative would end up being same as the connection for the positive on the bottom, right?

Exactly.

That means no charging both at the same time unless I missed something... ?

Recharge each cell at 4.2 volt at a time.
One at a time.

 

[Rando]

Exactly.


Recharge each cell at 4.2 volt at a time.
One at a time.

Ok, thanks for the confirmation of my suspicions.