I need to be educated about LED drivers.

I’d really appreciate it if someone could point to information on how to select LED drivers for my torch. Below are my questions for which I need info so feel free to answer them but if you can give offer up some reading material that would be great.
My questions relate to my Trustfire R5-A3, which comes stock with an XP-G R5, but now I have an XM-L2 which I attempted to fit. It seems that I need to swap the driver as well because a straight swap of the LEDs seems to has deleted all the modes on the stock driver.

1) What current capability of the driver? What is the benefit versus low, mid and high currents?
2) What chips; 7135 or single buck type sort of arrangement?
3) If I bought a 7135 type driver then how many of them should I have on the board; 4, 6, 8 and what are the advantages?


I saw from your other thread on the subject, where you finally did get the modes working properly.

If you are still interested in replacing the driver, I’d recommend the Nanjg 101 -AK driver:
This is a good driver for 14500 Lithim lights, you will not be able to use NiMH/Alkaline cells. The 101AK has 4x 7135 chips, giving a 1400mA current, which results in good output, but still regulated, giving you longer runtimes (Important with low-capacity 14500-sized cells). I use this light in my XM-L2 modded T20 which is similar in size to your host, and I find it to be a great match. A very nice benefit of the 101AK driver is the ability to disable the strobe/SOS modes.

The Nanjg AK47 is another good option, but with only 3x 7135s, will give you a lower output of only 1A:
It also has selectable mode groups, and will only work with Li-Ion cells.

If you wish to retain the ability to use Alkaline/NiMH cells, the Nanjg 110 is an available option:
…but is only a single mode driver.

I did a description of the different types of drivers a while back. Maybe it can be useful to you:

Thanks for the info, gents.

Lagman, yes I found your thread shortly after I started this thread.

Gents, I presume for my use, i.e. li-ion & single XM-L2 led, then a linear driver would be the best option?

So, all things being equal what are the pros and cons of increasing, or decreasing, the current capability of the driver when considering my spec?


A 7135 based driver (linear) will work perfectly for your application. How many 7135 chips you need depends on you.
Double the number of chips and you will double the amount of heat generated (can be bad) and you will get about half the run time. On the up side, you will get almost double the light output.
If you don’t need a lot of light, I suggest getting a low number of 7135 chips (4 for example).
Be sure to have a good thermal path between your new LED and the body of the flashlight!

Will increasing the chip count/MAh reduce battery runtime?

I am going to use Gelid thermal compound between the led and the pill. For the contact between the pill and the body, is metal to metal contact sufficient?
How many 7135’s/MAh could I push it to without something cooking?


I don’t know exactly your flashlight. But in general the critical point is the contact between the LED star and the flashlight pill. The contact between the pill and the body of the flashlight doesn’t need thermal grease as the surface of contact is much greater.

“Will increasing the chip count/MAh reduce battery runtime?”
I’m not sure I understand, but for a given battery, if you increase the number of 7135 chips it will decrease the runtime. Each chip will feed 350mA to the LED (and pull 350mA from the battery). The more chips you have, the brigter your LED and the quicker your battery will be empty.

Generally speaking:

More Current = More Brightness = Higher temperature = Less Runtime

On a driver using 7135 chips, each chip is able to allow 350mA of current to the LED. You can calculate the total Amp by multiplying the .350A by the number of 7135 chips on the board.

For a smaller light, with lower capacity cells, fewer 7135 chips are a better option, as they will limit the amount of current, and make your light run longer without dimming.

This type of driver would normally only be used on lights using Li-Ion cells in parallel. For lights using series connected (end-to-end) cells, you would need a different kind of driver.

Ok, thanks for the info.
Considering that my Trustfire and EVVA cells currently run about 30-35mins on high beam I think it is best to get a 3 chip driver or maybe a 4 chip.

I think I will buy both and go with the Nanjg’s; an AK-47A and a 101-AK-A1


Both look like good choices to me.