Head torch meltdown while not in use.
Added 2019-11-08 05:36:23 +0000 UTCIt's a bit disturbing when something you use regularly fails in a manner that involves shorting out the internal lithium cell.
After I'd made the video I explored deeper with a microscope as I couldn't see an obvious path of fault current. A closer look at the dark connection on the interface between the two PCBs suggests that a solder ball or near-bridge has probably shorted out between two connections and the high current has burned the two battery contact springs and the smallest track involved in the fault.
The solder bridge seems to have burned clear, destroying some evidence in the process and the 18650 cell doesn't look like it's vented, but has suffered thermal damage from the red hot contact springs at the ends. The internal condition of the cell is an unknown variable as a result, so I think I may discharge and recycle it or use it in a non critical application.
Comments
My first LED headtorch was a Petzl Tikka. The quality of construction did not match the price. But it served me very well once the switch had been rebuilt.
Big Clive
2019-11-18 17:10:23 +0000 UTCClive, I have a Petzl head-torch - not cheap but good quality and it's lasted years. Some things I think it's good to economise on, others not so much...
Gordo
2019-11-18 16:27:12 +0000 UTCI think the packing piece moves the battery center line so the spring contact is more on the battery center line.
2019-11-11 13:25:51 +0000 UTCI'm going to try and make the other head torch safe based on the issues discovered.
Big Clive
2019-11-10 14:21:11 +0000 UTCThe knife is a Giaco maker knife. If you look at the channel Giaco Whatever you'll see the videos where they designed and manufactured it.
Big Clive
2019-11-10 14:20:06 +0000 UTCNon technical question Clive. What make is the knife?
2019-11-10 12:16:46 +0000 UTCYou could modify the negative end-cap by fitting a switch to it. I'm assuming that the case isn't long enough for a cell with a built-in protection pcb...
Gordo
2019-11-10 10:23:46 +0000 UTCThe difficulty is getting the PCB out to do that. It looks like the end cap is pressed on with high force. I have experimented with sliding shims of thin plastic down either side of the PCB components from the battery loading end.
Big Clive
2019-11-09 09:39:33 +0000 UTCebay don't care about the things they sell. Their rules are all set up to maximise their own profit. Ever tried complaining about sellers which mis-represent their goods as being in the UK but they then come from China 10 days later...
Stephen Eyles
2019-11-08 22:12:02 +0000 UTCClive, would a couple of coats of circuit board lacquer be enough protection against shorting out on the case? Seems a shame to not use it if you like the way it operates.
Charles
2019-11-08 21:16:09 +0000 UTCmaybe a message to ebay and trading standards on possible fire risk to anyone if others can do the same or more damage.
2019-11-08 18:05:27 +0000 UTCI'm glad it didn't do it's heating thing while it was on my head. I'm also wondering if the aluminium housing could have failed catastrophically if it had vented. Not what you want on your forehead.
Big Clive
2019-11-08 08:44:04 +0000 UTCYeah. From their state I'd say they did physically glow.
Big Clive
2019-11-08 08:42:04 +0000 UTCYes it would. That's a good idea.
Big Clive
2019-11-08 08:41:28 +0000 UTCGet it on ebay as a second hand head warmer 🤣🥵
The Tinkering Shed
2019-11-08 08:02:18 +0000 UTCThe springs must have been red hot, like nichrome wires. Scary.
Jamie
2019-11-08 07:39:29 +0000 UTCwould a protected cell make this any safer ?
God 420
2019-11-08 07:06:21 +0000 UTCWater is an issue at higher voltages, but at the 4V this operates at I'd expect it to be much less of an issue. It'd cause corrosion, but probably not significant tracking. Definitely not enough to pass enough current to burn the springs.
Big Clive
2019-11-08 05:57:41 +0000 UTC
