14.8v power supply for TK45

[weegidy]

I have a TK45 as my mid-sized flashlight, it was the first high-end light that I ever purchased, and it is one of my favorites. I would, however like to switch over to LiIon cells though instead of the old-fashioned NiMh:laughing: that it is intended to be used with.

I know that the light also works with alkaline batteries which would mean that is can at least run with 12v. Does anyone here know if the light will work with 4x 3.7volt cells, or if I will burn out the circuitry?

My plan is to modify the battery holder to use 8x 15400, 2 sets of four cells in series. This would give me slighly longer run-time than NiMh cells would.

Thank you!

 

[Shadowww]

2500mAh NiMH's (Eneloop Pro 2nd generation) = 3 Wh, high-quality 14500's - 2.5-3 Wh.
You won't gain any extra runtime over Eneloop Pro's, only increased danger due to Li-Ion's being explosive.

 

[weegidy]

That is true, but 8 2500mAh eneloops cost $32. But I do get the confidence of using sanyo.

Just for the sake of argument, though - would 14.8v hurt the tk45 driver?

 

[Shadowww]

Try it? :P
People are using it with 8x Energizer Lithium's, and they have OCV 1.8V when fully charged (14.4V for 8 cells). So, quite possibly it wouldn't, but your best bet would be contacting Fenix support.

 

[Up All Night]

If you put four 3.7v (4.2v charged) li-ion batteries in series in a Fenix TK40, TK41 or TK45 say goodbye to your light!! These lights run 4AA in series, parallel of 2. They run on 6 volts! 16.8v = DON'T!! Stick with LSD Nimh.

Edit: I spaced on the fact that the TK45 is the Tri-Head model running 8AA in series.(TK41 on the brain) Your proposal of 4s li-ion would still be putting 16.8v where 12v is recommended. 3.7v is the nominal voltage for li-ions, off the charger they are 4.2v.

 

[Shadowww]

Uh, 2S4P array would be quite a trick to make in that battery carrier. :P

 

[Up All Night]

Uh, 2S4P array would be quite a trick to make in that battery carrier. :P

? I don't see 2S4P mentioned anywhere.

 

[weegidy]

? I don't see 2S4P mentioned anywhere.

I think he meant 4S2P as I mentioned in the original post. But either one would me difficult to make, not impossible though.

EDIT: What about using LifePo4, I think 4s LifePo4 is going to have almost the same voltage as 8s Alkaline.

 

[Shadowww]

I think he meant 4S2P as I mentioned in the original post. But either one would me difficult to make, not impossible though.

EDIT: What about using LifePo4, I think 4s LifePo4 is going to have almost the same voltage as 8s Alkaline.

Alkalines/NiMH's are 4S2P there, so Li-Ion's would need to be 2S4P to have comparable voltage (and even then, it'd be a little too high - LiFePO4 voltage would be perfect, but they don't have nearly as much capacity).

 

[weegidy]

Alkalines/NiMH's are 4S2P there, so Li-Ion's would need to be 2S4P to have comparable voltage (and even then, it'd be a little too high - LiFePO4 voltage would be perfect, but they don't have nearly as much capacity).

Alkaline are 8 cell, all in series. I would need 4S2P LiFePo4 if I would want to get this working. But I agree, all 14500 LiFePo4 cells are very low capacity. Maybe I'll just have to leave it as it is with NiMh. :( There would be significantly less internal impedance with a 4S2P LiFePo4 (than 8S NiMh), I'm not sure if that would be significant enough to overcome the capacity shortage though.