Abnormally Low Current Draw On Cree XM-L2 With Nanjg 105c

Flashlight Modding and DIY Parts
1

Today I got a Cree XM-L2 U3 and a Nanjg 105c (8 * 7135) with guppydrv universal in from Mountain Electronics today. I put the parts into a WF-502B and everything lit up just fine (2200mAh LG 18650 cell).

I decide to go measure the current on the 2% mode, because I hoped this would put the average current to a very multi-meter friendly current of about 60mA. However when I went to run my test the current only read to be 10mA. Similarly low current readings held in proper proportion for the 25% (~100mA) and 33% (~160mA) modes as well, putting my estimated current draw on 100% at 500mA.

Why does my light’s estimated max current seem to be 500mA when it should be closer to 3A?

2

what do you mean with estimated 100%?

Just do 100% and measure current

can you light up falling droplets in shower with a PWM mode?
after 4 feet the lit droplets should be spaced about 6-7mm when the timing is 19kHz

3

I can’t measure at 100% my multi-meter tops out at 400mA for current measurements. I can try to find another one though.

My estimated 100% is calculated that if a 2% PWM would use 1/50th the current of 100% then by multiplying the current on 2% by 50 you get the approximate current on 100%

10mA * 50 = 500mA

4

jesus a 400mA max load meter adds a lot resistance to the circuit

there is a lot voltage drop on the meter getting you too low readings

The AMCs do 2.8A PWM and your meter has a resistance of like 200-300mOhm
then you got a voltage drop over that DMM of like 0,75V

even with a 10A DMM the redings can be too low

5

The tail cap readings aren’t really valid in this case then. I should hunt down another meter.

Is there some alternate way I could approximate current or should I just not worry about it?

6

for a 20mm reflector light you should feel an uncomfortable heat after like 10 seconds lighting on a sensitive spot of your skin

the driver will work fine

7

Thank you very much for your help!