7880 Driver catches on fire!

That is very unexpected, what would have happened if it was in the light
Glad your ok, battery powered fire is serious business

its likely the light would have built up pressure, and most likely would blow the tail cap switch boot off, or the lens out.

It might be a test worth doing, perhaps it would extinguish the available oxygen and put itself out, or overheat and blow a li ion (or NiMH), its something i think worth testing (outdoors)

Is there a way to determine which component on the board failed?

I think the most likely conclusion to this fire is that it would put itself out quickly once a component “failed open”, ending the shenanigans. I could be wrong about that though!

Thanks for posting this, it’s interesting stuff.

I think that I have some of those 7880 drivers. In fact, now that I think about it… I think I even tested one some. It may be in an SK68 right now. As I recall the efficiency was low. Maybe very low, I don’t recall. I do recall that input current would increase with voltage while output current remained stable - that means that efficiency was dropping like a stone above a certain voltage.

I’d say it’s most likely an FET failed.

FWIW, I’ve just pulled a 7880 driver out and taken a look at it. I think that it may be a flyback driver. I’m basing this on the fact that the inductor has 4 leads rather than 2. Flyback converter - Wikipedia

its difficult to know what failed first, as the glowing-red hot coil burned everything underneath it.

The torrid coil definitely has two windings on it, (four leads) i have used this light quite often with no problems. And have other lights with the same driver modded in it. I like the modes settings it has, regardless if its inefficient of not. Though it did have really good run times on the lower modes with the three NiMH cells in parallel.

Now you can rename it to PadmeFire :smiley:

+ 1

I had my 7880 running on single d cell and they burn as well.

Its probably a forced boost driver and they limit it to small single aa cells only.

its probably what happened here, with the three NiMH cells in parallel the current supplied might have been to high. I also use this same driver in single-AA lights with no problems at all.

Can someone link me to anything that explains the term “forced boost driver”? Thanks.

I’m not familiar with the term “Forced-Boost” driver either, as i known this 7880 as a Regulated standard boost type driver. ( steps the voltage up from 1.5 to the voltage needed to drive LEDs.

honestly I’m just blabbering words here but it gets to the point lol

I’m glad I didn’t use the word overclocked boost driver
facepalm

Oh but not all components fail open! Biggest reason I avoid tantalum caps. They are not only fond of exploding & shooting flames but also fail short.

This 7880 driver explosion is probably not due to tantalum. Though don’t know what under the coil.

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.