TrustFire TR-J12 & C Batteries?

I have one of these on the way and was reading some of the earlier posts and had a few questions.

Is any one running this on c batteries?

Should I go ahead and place a heavier spring on it?

Are there any other issues I should be aware of that people have run it to after using it for 3-6 months?


No problems with mine although I mainly use 2x26650 (8.4V).

It draws more power and conversely sends more power to the LED array at lower voltages, as the cells deplete. I think thats the main attraction to using C-cells, you can run it at lower Vin, where its going to consume the most power.

DEFINITELY upgrade the +B spring. Even with the OEM driver it will draw up to ~6.5-7A at when Vin drops to around ~6.25V. Thats enough to anneal the +B spring, soften it so it loses its stiffness “K”. ALternately a strand or two of copper braid wrapped / woven around the spring will divert enough current from the spring coil.

I think theres some degree of variation across the BLF population though, because my light kicks into low voltage protection when the two 26650/18650 cells deplete to around 6V (3V per cell), and others have reported their lights running full-tilt at voltages lower than this.

Thanks, I have some 26650’s I plan on using but it’s nice to have the option to use batteries © I can get at the grocery store. Huge advantage when traveling .

Would it even work with c batteries given 3 would be 4.5 v?

Not sure about 3 x C, but 4 x C works! and is very comparable with my panasonic 18650s!

Check out my pics (comment #22):

Got mine to run on 4 C alkaline batteries with a small dummy spacer.