I’ve been out of the flashlight hobby for a few years but recently decided to mod one of my SolarForce Z2s for a specific need. I have 3 Z2s that I’ve used for years without any issue, one with a 14500 and though beat up from use it’s still going strong.
What I was looking for from the mod was a warmer tint, more flood, lower moon mode, mode memory and Li-Ion capability. No need for NiMH battery capability. Difficult to find in a 12mm driver.
I settled on MTN-12DD FET driver fully understanding the limitations of a FET driver in such a small light. Also ordered an XP-L2 4k and MTN XP 12mm Copper MCPCB.
My soldering skills had diminished a bit since I haven’t been working with these small components in a while and I created a solder bridge between the - pad and ground when I first flowed the XP. Luckily I bench test everything as I go and found it with a multi-meter before I assembled anything. I re-flowed the LED and all was fine. Final bench test with the MCPCB mounted to a CPU heat sink showed about 2.5A with an AW 14500.
I assembled the light using Artic Silver thermal compound, the driver was soldered to the brass pill. I also bypassed the switch spring, not for max output but because I thought the spring may loose its temper quickly if I ran the light on H (I will need to see what it can do at some point!). Final test of the assembled head showed the same 2.5A on H with the same 14500.
I used the light for a couple of weeks of normal use, normal use being a few minutes each evening on Moon or Low mode. I did test the higher modes a few times but literally no more than 5 seconds on H and at that only 3-5 times. In that short time the light begins to heat quickly.
A few nights ago I noticed on L mode the light was starting to flicker, no going off but between L and approximately Moon mode. After a minute or two of this the light appears to be below Moon mode output wise. The strange thing is in this condition the light still has all 4 modes, just very dim. Leave the light off for a few hours and it will return to normal for a short time.
The issue is becoming more common, occurs regardless of which mode the light starts in, it will eventually start to flicker and dim. The time it takes to start flickering does not seem dependent of which mode it starts in, Moon, L and M all appear the same. I haven’t tried it on H because I would expect that to tax the LED due to heat. I have tried 3 different batteries with the same result. The LED looks OK, no discoloration and uniform in color as is the output.
I had some time to do some testing today and believe I’ve determined the problem.
Testing battery draw:
Normal Operation
Moon 0.020A
L 0.090A
M 0.430A
H 2.500A
Incident Operation
Moon 0.002A
L 0.003A
M 0.006A
H 0.016A
Testing V available at LED:
Normal operation
Moon 2.41V
L 2.47V
M *
H *
- Light would no longer work normally.
Incident operation
Moon 2.42V
L 2.50V
M 2.85V
H 4.10V
My conclusion, based mostly on the voltage at the LED on high mode is the LED is the culprit. I’m thinking I may have damaged it during my ham-fisted attempts to reflow it. Odd though, I’ve cooked LEDs in the past but never had one behave like this.
I’m open to opinions.
Sorry for the long read, just trying to provide all the info.
Thanks