7880 Driver catches on fire!

I modded an old plastic incan billy light last year. The type that took a 6V lantern battery.

It's now running an XM-L and one of these drivers - powered by 8AA Eneloops in parallel for runtime.

The emitter is mounted on a PC chipset heatsink but the driver is simply sitting in place held by hot-glue.

I don't often run it at max, but perhaps I should do some spot checks on the driver temperature before leaving my latern unattended. Thanks for the warning DBSAR!

Do you mean to say the light was still working, until you turned it off?

Of course not! Fortunately only one needs to fail open. Or desolder itself, or whatever. Like I said, maybe I’m wrong… but that’s where my money would be: I would bet that the driver (as a unit) would fail open rather than build up enough pressure to pop the tailcap.

How much current is running to the LED on turbo? (and how much current draw from Battery) With rough estimate of driver (in)efficiency may be enough to glow a toroid.

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.

The specs stated 800ma, though i measured 1.02 A on fresh charged cells to the 219 on highest mode.

The LED went out when i heard the “pop” sound, then i noticed the glowing inductor coil and the flame from burning insulation and resin.

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 just be a cold solder joint and with the leads being so close to each other, when it came loose, it just touched up against the other.

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.

A modest drive level… :slight_smile:
…so that’s about 2.6 Amps from a 1.25V Battery at 100% eff. 80% driver eff would put battery current at 3.1+ amps.

A few minutes ago I took a brief glance at CPF and saw mentions of 75% eff. I assume measured. So a little higher battery current even.

A measure of the battery current will tell how much energy is lost as heat into the driver.

? No, a measure of the:

  • input current
  • input voltage
  • output current
  • output voltage

all at basically the same time would tell you that. Just measuring battery current doesn’t get us very far.

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?

I don’t know anything for sure, looking hard.
Most of what I’ve found lately is at http://www.aliexpress.com/popular/ldch.html

Not sure what the difference is between LDCH-20 and LDCH-30
http://www.aliexpress.com/item/LD30-flashlight-driver-circuit-board-CR123-version/32255534881.html

Looks like the LD20, DX SKU 7880, and RV7 are the same thing.