So how exactly did you boost your light? only resistors which gave you like 400 lumen + you said went to 4.7A effective afaik, now you got it to 5.5A?
Vihn told me my TK75vn was pushed to 4.5A
Yes i know, but is that with resistors only? or he modded the driver?
What about the TK 61? do you have any info about max amp without modding the driver? thanks.
I didn't mod the driver. Sorry, no time to test much yet... All I did was de-dome and resistor mod.
What did rdrfronty measure in lumens? Though it was like 1,700? If so, no way, no how is it as 4.5A -- more like 6A+, because the TN31 was at 6.5A supposedly, and also around 1,700 lumens. I can understand a little bump in lumens for a bigger reflector, but not a lot. Sorry - no time right now....
Thank you! actually i only care about some general safe limit, i know you said its a risky thing to do and i should understand that, and i do….but i guess 4.5A should be fine for short runs on turbo ~ 1min? i never use it more then few mins on turbo, any light i got, only when i was testing my TK 75 runtime.
If my friend go to 4.5A from 3.1 stock, should i get like 30% + output generally?
OOPS!!! I forgot this is the TK61 thread!! I also have the TK61vn . Factory is 3.1A Vihn pushes it to 5.75A!
Ohh, ok. The TK61 reflector is about 81mm I.D., while a TN31 is about 66 mm (just measured both).
Crap - ok, so I got a tailcap of 2.75A, theoretical 5.5A to the LED and measuring only ~480 kcd at 5 m. I'd expect more if vinh is doing 5.75A - dunno if calculated from measuring at the batteries or measured at the LED though, but could be getting some loss's somewhere, maybe focusing, maybe loss of power to the LED. Thinking vinh measured at the LED -- I know he's done that before.
If I knew what resistor values he used, I'd know more perhaps. But of course if he swapped out FET's, that may effect the resistors compared to the output to the LED.
Converting tailcap amps to emitter amps in combination with a buck driver is like doing lux measurements by holding a light meter in one hand, a thrower in the other, stretching out your hands to roughly 1 meter between them and take a measurement.
Its not accurate, its not "effectively" or "theoretically" the same as doing it precisely from 10meters.
You dont know the efficiency of the buck driver so there is no way to know if its accurate. Doubling tailcap current in two cell series lights just happens to often be quite accurate on many typical budget lights driven to 2-3 amps and with freshly charged cells. But its not always the case. With a very efficient driver (like LD-29) emitter amps could even be higher.
Lets look at some examples.
Example 1:
Emitter current 3A on Noctigon. Vf is 3,4V (Vf number by djozz)
Energy at emitter =10,2W
Tailcap current 1,5A x2 cells at 4V (with load)= 12W Energy input to driver
Efficiency is 85%.
Example 2:
Efficiency is 85%
Emitter at 6A and emitter Vf at 3,9 (VF number by djozz)
Energy at emitter= 23,9W (notice that required energy at 6A is more than double of 3A due to the higher Vf)
23,9W/0,85= 28,11W input is needed if driver efficiency is 85%.
3,6A tailcap curent * 3,9045V (with load) * 2 batteries=28,11W input.
(I assumed voltage sag under load. Numbers above may not be 100% accurate, but should give a good picture.)
-1,5A tailcap current from two cells equals about 3A at the emitter with 85% efficient driver
(Simplified, saying 1,5A *2 cells= 3A emitter current is spot on in my example)
-3,6A tailcap current from two cells equals about 6A at the emitter with 85% efficient driver
(Simplified, saying 3,6A *2 cells= 7,2A emitter current is way off)
I never assume emitter amps with buck drivers, I doubt vinh does either. Especially not when he specifies emitter amps.
Always measure at the emitter at this level instead of using simplified assumptions. Efficiency of buck drivers often range from around 70-95%. And even if you assume 85% or 90% or whatever efficiency, its not as simple as to just double tailcap amps to get emitter amps. It only works in certain situations.
Okay