Noob question - series and parallel

Hello all!

I am completely new to performance flashlights. My first LED light was a Fenix TK22, which I mounted to my wife's home defense scatter gun. After mounting a very nice light that sees limited use, I became disappointed in my trusty Maglite 4D's that I keep.....everywhere.....night stand, vehicles, emergency kits...Maglite 4D or 3D and extra batteries are there.

So flash forward to last week, a friend recommended an upgrade, a Solarforce Gladiator and K3 MT-G2 head. $100 for spotlight that swings like a 4D? LET'S DO IT!

Then my OCD kicked in. I noticed that while the Gladiator can accept up to 4 18650 batteries, using the K3 head, I could only run 3 and a spacer, otherwise I would be pushing too many volts. So on to my question. Could I run 4 batteries in a parallel-series-parallel configuration, which should yield 7.4V and approx 4000mah (depending on batteries)? If it would work, is it safe? Will it still produce the advertised 1500 lumens with significantly longer runtime? Please explain why or why not, so that I can learn, as I'm electrical and circuitry stupid (my greatest triumph when it comes to electronics has been hardwiring an aftermarket stereo into a car, because the jackwagon previous owner had cut the harness and done so as well). Further reading material would be great also!

Re: Noob question - series and paralle

Welcome here, omegis13! :wave:

Do some reading over at Battery University, in particular these chapters:
Serial and Parallel Configurations
Protection Circuits
Safety Concerns with Li-ion

Also CPF itself has an entire section with many threads on how to use Li-ions safely in parallel or series configurations:
Flashlight Electronics - Batteries Included

The main point is to use cells with closely matched capacities, in the same State-of-Charge, monitor individual cell voltages regularly, and use either protected or safe chemistry cells.

That's apart from how to wire it up. In this case, 2 cells parallel, and two of those 'packs' in series seems most logical. But this is in a light where 4 cells are stacked in a row, correct?

If all this is going above your head, the safest course of action is not to do it. But again: do some reading, to see if it all makes sense. :thinking:

Re: Noob question - series and paralle

Thank you for the safety information.

RetroTechie said:

That's apart from how to wire it up. In this case, 2 cells parallel, and two of those 'packs' in series seems most logical. But this is in a light where 4 cells are stacked in a row, correct?
:

Click to expand...

Correct, the cells are stacked in the tube. I have access to a pretty well stocked machine shop. Once I have the tube in hand, I'm going to see about making some sort of pods that will hold two 18650's securely and wired in parallel, then run two pods in series. I can also bore the tube to a larger ID if necessary. Worrying about making it fit seems down the road from understanding whether the LED and driver can even handle the power I'm wanting to generate and what kind of performance I could expect. My friend sent me a copy of the LED's data sheet from Cree, but it's all Greek to me.

http://www.cree.com/~/media/Files/Cree/LED Components and Modules/XLamp/Data and Binning/XLampMTG2