Do I have to make one? 3C parallel adapter

I want to run 3 x 26500 IMR cells in a parallel configuration in a 3D maglite.

Does anyone sell or make an adapter for this? Or do I have to make something myself?

Hi, that is an interesting configuration. I have not seen that setup yet, but have considered similar configurations.

If you decide to build it, please consider to add a reverse protection diode to each cell so they don't accidentally reverse charge a low cell.

I didn't know reverse charge protection would be necessary.

I've seen other builds with 2 parallel 26650 without reverse charge protection. Is 3 cells any different?

Can anyone else comment on the need for reverse protection diodes??? :wave:

I'll be charging each cell individually.

I have read a number of posts which suggest parallel cell configurations are ok.

eg. https://www.candlepowerforums.com/threads/258282

https://www.candlepowerforums.com/threads/264321

I did something like this


I think that the protection diode is a good idea with three cells. You could probably add one without too much more trouble.

Hi, like anything else for Li based cells, the diode is just adds a protection layer. If the 3 cells are in fact closely charged, and relatively closely balanced in performance, then the diodes do nothing useful.

If for some reason, any reason, the cells become mismatched, then current can flow from the higher voltage cell to the lower voltage cell. Since these cells are made to recharge, you might normally think that is not a problem, and it might not be if the difference is small.

If the voltage becomes substantially lower in one, then the current into it could be rather high, and of course, that will likely be the one that is mis behaving in the first place.

The IMR cells I think are a bit safer than the nomral LiIons, but I am not experienced with that cell type. What do the r/c guys do? They are the real power users of cells, so that is where I would seek guidance. Perhaps if you ask a mod to move this thread to the battery / electronics section, more responses will come.

3C parallel adapter /

So the diodes would go in series with each cell?

Won't that result in a voltage drop? That might drop the voltage too much for a direct drive setup??

3C parallel adapter - need reverse charge protection diodes?

So the diodes would go in series with each cell?

Won't that result in a voltage drop? That might drop the voltage too much for a direct drive setup??

Hi, if you imagine each finger of your hand being a cell, then there would be a diode at the finger / hand joint for each finger.

Yes, there would be a 0.3 - 0.5 V drop for the diodes, if they are properly sized. You didn't mention the LED setup you have in mind, but I am assuming a healthy one or you wouldn't bother with 3 cells in parallel.

It isn't too hard to wire this up with some tape and cardboard and see if you are happy with the result or not.