Are you using the same 7880 Driver ?
I believe i discovered what happened in this case, the lead wires to the LED solder points are so close it loos like heat build up caused them to short together, meaning its not a fault in the driver. (Though it would be a good idea to check how hot yours is running considering eight Eneloops in parallel can send a lot of amps into a driver.
Good find DBSAR. That appears to jive with what I found previously with the efficiency dropping as input voltage went up. Maybe it’s more along the lines of efficiency dropping as boost ratio is reduced decreases. A dead short at 0.8A on the output would more than flip the ratio on it’s head.
could be that too. ( as visible in the second photo you can see the red lead lifted up off the board (with the nearby tan-colored resistor) and contacting the black - lead.
We do have a measure of LED current at about 1A. A 219B runs about 3.25 watts at 1 Amp. …just curious if there is enough wasted heat on the driver to melt a solder joint and cause the short. Knowing current from the battery would get a close approximation at this point.
I am going to run the test again with a new 7880 driver in the light, but this time i will monitor the head from the driver closer with a infrared heat meter. if it gets really hot again i will try resistoring the current back a bit until it runs cooler.
Curious if you got to that test of those drivers for NIMH.
I’d been thinking they’d be good for gifts to non-flashaholics with kids
But only because I thought they’d be less likely to catch fire ….
I still use these drivers in various lights with no problems. i also replaced this one here with the same driver in the padme and its working no problem. I have not ran another test on maximum mode yet however to see if it survives another test. Do yuo know of other good 1.5 volt boost drivers with good modes?