Charging 4x 18650 with IMAX B6

So the title says it really. I’ve got a generic 4x 18650 battery pack used to power a twin led bike light - 2s2p I think. Could I charge this with a IMAX B6 if I got a cable with banana plugs and a 5.5mm plug?

It does have a charger, but I’d like check mah in and out.



For charging serial connected cells you need to balance the cells.
Because if the cells are not exactly identical, when applying 8.4v on the pack terminal 1 cell (or group of cells connected in parallel) with higher capacity can be charged to 3.9v while the cell with lower capacity already fully charged and now 4.5v are applied to this cell aka over charged and it may be dangerous.

This issue can be solved in 2 ways:
1. Balance the cells using the balance charging mode of the IMAX (requires an additional balance cable from the pack, connected to 0v, 4.2v and 8.4v)
2. Charging using regular 2s mode of the IMAX and counting on internal BMS to balance the cells.

Unfortunately all the cheap 2s2p bike lights packs I know does not have an internal balance BMS, only a protection board :(

Hmmmm…. So I wonder how the simple wall mounted charger supplied with battery pack gets over these issues.

Post a picture of the battery pack—-I’m sure the pack has some sort of BMS — can you check it’s voltage or tell us what output the power supply is

The pack will likely have ‘some’ kind of BMS. How…good….the BMS and the cells are is a different matter. 2S2P is a common configuration for those bike packs. I’ve seen canisters that you can put loose cells in with the BMS built in.
The IMAX for charging will not be really any different than the stock charger. Maybe a tad safer.

Yes, you can rig a new plug setup for it and do charge/discharge testing. I have an Accucell AC6 (very similar) and a charge setup that looks like an electronic octopus for charging all kinds of stuff. You will actually be able to tell more about the functioning of the BMS and stock charger by looking at the results with a more accurate charging system.

Note-my personal preference is for a balance tap. I’ve seen a number of packs go bad when the BMS failed. No pack ever went ballistic. It just didn’t balance the pack properly, and the weakest cell finally made the pack inoperable as it continually got shortchanged in charging. When I tore the pack apart and checked individual cells, they were all OK and went on to have continued use in a pack with a balance tap.

Yes this is interesting, I was thinking of adding a balance lead. Do these things have a standard plug? Would it have 1 red and 2 black leads?I guess it’s a question of soldering the leads into the right places…

If you’re able to solder leads to the cells , you should be able to see how balanced the cells are before and after a charge with a DMM— you should also be able to do a capacity test just by connecting to the battery’s cable — you’ll get a more realistic capacity from the way you’re using the pack —- I’d be careful using balance leads with a BMS still hooked to the pack —- I had no issues with my IMAX B6 , BUT when I did it with my ISDT Q8 it locked up the screen and made the charger unusable —Luckily I was still in my return window with Amazon

Useful stuff… Thanks so much for your help guys.

I think you don’t want to use a BMS and balance tap simultaneously. Never done it, so can’t say definitively. Seems like a potential conflict there.

Here’s how they are wired up. Got mine from RC dealers. Just wired up 2x 4S 21700 packs for a weed whacker yesterday replacing dead 18v NiCad pack. Works great.