How to Fry a Flashlight? I Did it By....

This thread actively solicits stories and comments by flashlight fans. Please state exactly how it happened, if you were able to fix it or whether it was able to be repaired via the warranty. Also, whether you think it was YOUR fault or the fault of the MANUFACTURER.

Meanwhile, I have some questions if anyone can address them:

1) If using too much voltage (two CR123A batteries in a light designed for 18650, for example), how long does it take to fry the flashlight?

2) When putting batteries in backwards in a light with no polarity protection, how long does it take to fry the flashlight? Does the light have to be turned on? Does the flashlight DO anything, or does it just die?

3) Since many flashlights are sold without instructions, or are sold with pathetic instructions, how much responsibility does a manufacturer have if polarity reversal fries the flashlight?

Thanks for any inputs....

1) pretty much instantaneous with anything more then 30% over designed voltage (well, except for some bulbs designed for long lives, but most flashlight bulbs are made for efficiency instead of life)

2) don't believe it matters, it just increases resistance alot.

Regarding reverse battery insertion causing a flashlight to fail--there are four basic issues that I see...

1. Mechanical--I have had old (& cheap) flashlights that would not work if the flat end of a battery is inserted towards the head because of the plastic on the bulb holder held the battery back (positive end of battery has nib that fits in). Obviously, no damage.

2. On a multi-cell flashlight--Like a 6D Mag or a 3 cell CR123--installing one battery backwards in the pack will reduce light output and "overcharge" the one battery installed backwards. If the battery is not immediately turned back forward in the tube--the battery will eventually be ruined.

3. LED flashlight (unregulated)llDepends on the reverse voltage that the LED (basically a diode) can withstand. A single cell flashlight driving a red LED--battery installed backwards--no damage. But a multi-cell (or lithium cell) battery installed backwards that exceeds the reverse voltage rating of the LED--will probably destroy the LED--no light, possibly smoke released.

4. Regulated Flashlights--If there is no mechanical protection (ring that allows positive nib only to make contact) and if there is no reverse polarity protection circuitry--yes, you will most likely "smoke" the circuit (no flash of light) if the batteries are installed backwards.

I believe that the manufacturer must mark polarity (on body, tail cap, and/or head) if reverse polarity will damage the light. Paper instructions are not enough (who keeps instructions with their flashlight). A reliable light will have either mechanical or electrical protection against reverse battery installation.

A flashlight without reverse battery polarity protection that destroys the light--is not a reliable light that you can count on. Sure, you will probably get it right when sitting on the couch replacing the cells--but in the middle of an emergency (fire, earthquake, etc.)--I would not guarantee correct battery insertion.

-Bill

I agree. I generall put the negative (-) towards the spring, but I have seen flashlights with very odd connectors. It appears as though few people have actually fried them, though. I also understand that rechargeable batteries often times don't work with incandescents, like the Surefire G2. Even then you don't really fry it often. The bulb just turns another color and dims.

It would be nice is manufacturers would put a + or a - at the top of their lights.

Also, in my case, had our youngest daughter decide that ye'ol family red laser needed to be washed... Took apart, dumped the cells to dry... Now what, the laser head has a spring on it--was the for the positive or negative end of the battery--heck if I remember. Flip a coin and stick + towards head/spring and press button. Lots of red and no smoke.

Darn--(I think)--wanted an excuse for a nice bright green laser. Oh well, maybe next time.

-Bill

I learned from an early age that most flashlights don't do well under water, despite Lloyd Bridges underwater television show. As a Boy Scout, I had a flashlight that looked (and functioned) more like a periscope. Unlike a periscope, however, it also didn't do too well in the rain (neither did my trusty...er...rusty...Boy Scout knife).

As for green lasers, what I've read about them scares me to death. The ones without IR filters, that is.

I fried a Shark driver and a Royal Blue LuxV LED when I switched to a new battery combination. It was totally my fault, I didn't stop to think or to measure. In the old combination I knew the LuxV had a Vf around 6.3 volts. I decided to switch from 3 alkaline D cells to a Magcharger pack of 5 nicad cells. My only thought was "5 nicads at 1.2v each is 6v which is less than 6.3v so I'm good to go". If I would have put a little more thought into it, I would have remembered to take into account the freshly charged pack voltage was higher than that. With Vbatt higher than Vf, the Shark went into direct drive, overpowering the LED. At first there was no problem. I was just playing around using the light in short bursts, nice and bright. Then I left it on and after about a minute and a half, out it went. THEN I finally started thinking and realised what I had done. So then I started troubleshooting to see if I had burnt out the driver, the LED, or both. And don't you know, I made things worse. While testing at the driver output to the LED, my test leads slipped and I caused a short somewhere because I saw a bright flash from the sensing resistor on the driver. I was able to repair the driver by soldering in a new sensing resistor and I am now using it to power a new LuxV LED, the old one was dead.

Just recently, I killed a second Shark driver. I started by accidentally lifting a solder pad while removing the installed adjusting pot to replace with an external pot. This broke one of the traces. However that was a fairly easy fix by creating a solder bridge across the break, so I went ahead and installed it. Then once it was connected to the LEDs I found it would only put out about 300ma at full output instead of the normal 980ma. Since I had a spare, I decided to get the light working by replacing the entire driver and troubleshoot the bad one later. Don't you know, as I popped out the bad driver, the screwdriver slipped and I broke another component off the board. I did a quick solder job to put it back on, but now the driver doesn't work at all. I haven't done any further troubleshooting yet so I don't know if it's dead for good. The good news is that the replacement I installed works like a charm.

Just a few minutes ago, I let the magic smoke out of a bike light I was building. Modamag helped me assemble the sandwich, but we left the LED terminals disconnected, waiting until we could get together to make a small heatsink. I got impatient, and did it myself just a few minutes ago. Although it initially worked, I did a really sloppy job:





Then, I tried to put the (aluminum) McR17XR reflector over it. That bridged the connections, then I heard a POP and a puff of smoke wafted away. I don't know if the board is fried too or if it's just the emitter, but I don't have nearly enough skill to desolder the emitter board (and I don't have any other spare emitters).

I prefer modding incans, because they're larger, simpler, and cheaper.

This was my first time working with LEDs.

TigerhawkT3 said:

Then, I tried to put the (aluminum) McR17XR reflector over it. That bridged the connections, then I heard a POP and a puff of smoke wafted away. I don't know if the board is fried too or if it's just the emitter, but I don't have nearly enough skill to desolder the emitter board (and I don't have any other spare emitters).

Click to expand...

You shouldn't have hurt the LED, but the converter is toasted. The converter may be fixable depending on what converter it is, though that will require some good soldering skills.

I put two of AW's Life PO4's R123's in an E2E and fried the bulb instantly. Learned that lesson the hard way.

I think I killed a Mag Solitaire drop-in by holding a powerful harddisk magnet very close to the light while it was on. I've read the magnet can mess with the core of the boost inductor (saturating it), resulting in an abnormally high inductor current. Not completely sure if this was the actual cause though, because it stopped working after playing with the magnet, but not immediately after.