Recently got a ULTRAFIRE WF-501B for night riding when out on the mountain bike and its ideal for what i need. The first ride went well it was cold but not freezing. Did a ride yesterday and the torch was a nightmare the temp was –4c ! plus the wind chill factor.
The torch refused to light maybe the odd flash and after a few tries i screwed it slightly apart and got it working on low beam then as it got darker i managed to switch it on high the only drawback was hitting bumps would change the mode not a big problem though. One hour later the torch is oh high mode but failing badly on / off etc and going really dull the arcing bright until it became unusable and the mode switch stops working tried the spare battery in it but this only made it worse.
When i got home i let the torch warm up breifly and it worked fine all modes selected no dipping and bright as new.
Just wondering what is the problem is as simple as the torch is not designed to go that low (cant find any working temps on this model) or is there chance of improving it? better batteries etc
A general rule of thumb is that if a chemical reaction is exothermic (gives off heat) then that same chemical reaction will speed up with heat and slow down with the absence of heat. We know that Li-Ion cells will heat up with use, so therefore it is possible that the cell does not perform well enough in the extreme cold that you experienced.
It also seems there are some connection issues?? or perhaps the driver components are sensitive to the cold?
Extreme temperatures can really cause unexpected effects.
A couple of years ago in extremely cold weather, the starter on my snow blower quit in the middle of cranking the engine. Later when I disassembled it I found that the epoxy holding the windings in place on the armature had cracked causing failure. Thermal shock not doubt from the rapid heating during the cranking!
NOW that I just finished typing all this I noticed that your temperature was –4C, not –4F. That’s not THAT cold! So I don’t know
It's probably not the batteries. Li-ion batteries discharge really fast in the cold. That wouldn't cause the on/off blinking behavior that you described. What you described sounds more consistent with an intermittent contact problem. Probably caused by something slightly loose in the switch assembly or a problem with the switch itself.
I have a Trustfire AK47 (9 LED) that did the same thing last night. It wasn’t that cold, only 40F. The light was left outside for a number of hours. It would blink once then not turn on at all. Same thing this morning after leaving the light in my car overnight. I took it apart, cleaned the contacts… Still nothing. Tried another set of batteries and it worked! Then I wiped off the battery contacts of the original set and voila! It worked. Maybe an issue with temperature, maybe an issue with dirty contacts. Light is only a week or two old, batteries were at 4.15v. I never had this problem before and it’s not like 40F is unseasonably cold. I have left the light overnight in my car every day under similar temperatures (+/- 5 degrees F) with no problem. More than likely it was dirty contacts in light or the batteries.
I used my ShiningBeam Blaze with a Pana 3100 mounted on my airsoft M4 during a game few weeks ago, it was –8c, used the light for a good 45min at MAX and it was not even down to 3.7v at the end, worked perfectly. Don’t know if it’s your battery or your flashlight …
just a bit more info we were using 2 of the same torches both had the exact same problems both are less than a week old (purchased together). They were bough in the u.k from a recommended seller and the batteries are protected xtar 3100ah.
The only thing i know for sure is the problem only occurs at temp below freezing so maybe its shrinkage of the working parts that are making a poor connection ? Seems the fix is not go bike riding in freezing temps lol
Some 501B’s have a “slug” installed between the spring on the pill and the battery. I have always removed this so that the spring touches the positive cap on the cell. Try removing this, see if it helps.
No slug in mine, I dont really need to use it in cold weather but its nagging me now lol
Put torch in Freezer for 5 mins and it would not turn on at all stripped the front sections of the torch down and it lit up occasionally flickering which is what i had to do on the ride. That got me thinking it must be something to do with the contacts/springs so i stretched the springs out slightly and popped it back in freezer for 5 mins unfortunate the results were the same
Rather that stripping the front of the torch i unscrewed the switch at the rear and the torch flicked into life screing it back in it kept lit but mode selection was poor and the light was surging. I unscrewed the rear right out and held it in place worked 100% lol results maybe just becouse its warming up quick indoors but it definitely seems to be a contact somewhere???
Cheers Steve i managed (just) to undo the retainment ring so i guess not!
Before i read your post i gave it 20 mins in the freezer it was totally dead i removed cap then put it on 1 thread and the torch came back to life screwed the tailcap back on it became hit and miss. Will tighten the ring if that does not help try the paperclip trick.
Can i kill the torch / battery by freezing too long ?
EDIT
After leaving torch in freezer whilst tightened retaining ring in switch i refitted switch and torch worked 100% so either that cured it or its the button as this would have been warm getting closer lol
Thanks Steve that was the problem and totally cured the torch i rang my mate who’s was worse than mine and we now have 2 fully functioning torches that work in the cold !
