I have Two Ultratac K18 AAA flashlights. They are for my keychain. One is stainless steel and it has an electronic lockout. The other is Alluminun and it doesn’t have that lock out. The lights are about five and a half years old. The one I had been using was a stainless steel version. Put a brand new battery in and went to use the light a few days later and it was dead. I was most certain that the light wasn’t left on because of that lock out. Check voltage and it was 0.528 volts! Put in another battery brand new. Both are 10440 lithium ion batteries. A few days later I went to use the light again. Dead as a doornail! Check voltage and it was identical at 0.528 volts! That proved that it is not the battery. Something wrong with the electronics of the flashlight.
What failure would cause the battery to drain dead within a few days when it’s left in the light. It’s not parasitic drain, something failed inside of it.
I revived both batteries. But I believe I should recycle them. Probably have cell damage. I can’t recall the name of that term / process when they get so low like that then the cells get damaged.They cells degrade by crystallizing?? Something like that. Not worth keeping for only $3 a piece!
Yes…dendrites was the word I was looking for. But that was a Result of the internal mechanisms of the drivers/flashlight failing resulting in batteries being drained extremely quickly and killing them. The batteries were brand new when they went in. So what happened inside the flashlight where it killed the batteries very quickly?That is my question?
According to this review it uses a PWM driver to control the 3 modes
So that means there is a transistor (likely a FET) on the board. There may be reverse protection also but i haven’t seen the board to tell. It is possible that the FET has a fault and it is draining the cell.
does the light still work using other cells/cell types, etc?
[edit] the 0.528 volts is typical of a diode drop; most FETS have a body diode built in. It could be that is the reason it didn’t go to zero—the diode would quit conducting below the drop voltage.
No… but it has nothing to do with parasitic drain. I’ve had these lights since February 2016. The batteries have stayed in there months without me having to charge it.
The other one works fine. It was absolutely not from accidental turn on. The stainless steel version which is the one that failed, has a mechanical lock out like I said. That was always activated. I use this light for about 5 years. I guess it serves its purpose!
or you dropped it and something has moved to a different place
for instance an inductor is frequently glued on
if you drop it it may come off and go touch something bad
or a piece of the case is bent and touching something bad now
maybe you have battery corrosion and that is conductive at the power inputs
or a circuit trace has shorted to another one, maybe with greenish copper sulfate
corrosion
The batteries are definitely not corroded… Nothing wrong with the wrapper where it could Short things out.
Who knows! I don’t have the skills to take it apart and test it. All I know is it’s history! I’ve just always been curious and want to know the reasons why.
I thought stainless steel would have been heavier also. According to that chart I got the info from, my stainless steel version is 2.933 times heavier than my aluminum one.
If you are interested i would be willing to trace the schematic and figure out what failed, then make the repairs and return it to you.
Aluminum is about 1/3 the density of steel, but the mechanical properties are also low such that an aluminum part has to be 3x thicker to have the same strength and load-carrying ability as steel. The heat capacity of aluminum is great which is why it is used for heatsinks, but it’s coefficient of thermal expansion is about twice as much as steel.