18650 li-on battery works in my 4 x AAA flashight - is it safe to use?
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That is true. The rechargeable version's voltage is 3.7 (volts), but for a non-rechargeable lithium battery's voltage is 3.0 (V). The OP put three AAA 1.5-volt batteries (= 4.5 volts), plus one 3.7-volt 18650. Total voltage = 8.3 volts. It means that he's running the flashlight's LED by over 2 volts (out of the flashlight design). That flashlight can only get hotter since the LED is being overloaded. It will be slightly brighter, but will get hotter sooner.
The flashlights designed for the use of Lithium batteries need to have a housing that aids dissipate the heat produced by the LED. It makes no sense to use batteries the are outside of the flashlight specifications. Even a regular LED flashlight that uses Alkaline batteries can get hot in one's pocket if one forgets to turn it off, or if left turned on for several minutes at a time.
The OP is pushing the envelope
OK, that makes more sense. From the way the OP was written, I thought only the 18650 was being used.
I can just about guess what will happen. At some point in the middle of the night, the circuitry will overheat or partially fail, and the LED will strobe for a while before going dark.
You should be just fine with the single 18650 (3.7v vs the 6v of 4xaaa), and much happier with it's longevity, and the fact that it's rechargeable.
IF the light has an electronic current regulator (which is likely) , it'll accept the 3.7v just fine (the LED emitter is likely rated 3.3v or less but current limited).
Some of these type flashlights even come with a plastic sleeve to better center the 18650 when using it instead of the aaa pack.
I love the 18650 cells; have tons of them onhand from disassembling old/bad laptop batteries (that usually only have a single failed cell and 3, 5, or 7 other good ones).
The flashlight could very well be brighter with the 18650, as typical aaa's cannot provide a lot of current, and the 18650 can certainly deliver plenty of current for a led emitter whilst maintaining it's full 3.7v output.
I have a ton of the wf-502 flashlights as well - cheap, almost indestructible, last forever, and plenty bright with a single 18650 battery. I've got ones in green, red, and ultraviolet as well.
You should be just fine with the single 18650 (3.7v vs the 6v of 4xaaa), and much happier with it's longevity, and the fact that it's rechargeable.
IF the light has an electronic current regulator (which is likely) , it'll accept the 3.7v just fine (the LED emitter is likely rated 3.3v or less but current limited).
Some of these type flashlights even come with a plastic sleeve to better center the 18650 when using it instead of the aaa pack.
I love the 18650 cells; have tons of them onhand from disassembling old/bad laptop batteries (that usually only have a single failed cell and 3, 5, or 7 other good ones).
The flashlight could very well be brighter with the 18650, as typical aaa's cannot provide a lot of current, and the 18650 can certainly deliver plenty of current for a led emitter whilst maintaining it's full 3.7v output.
I have a ton of the wf-502 flashlights as well - cheap, almost indestructible, last forever, and plenty bright with a single 18650 battery. I've got ones in green, red, and ultraviolet as well.
OK, that makes more sense. From the way the OP was written, I thought only the 18650 was being used.
I can just about guess what will happen. At some point in the middle of the night, the circuitry will overheat or partially fail, and the LED will strobe for a while before going dark.
It could happen, specially if the light is kept turned on for extended periods of time. Bright LEDs can get quite hot, so the brighter LED flashlights need to have more heat dissipating materials between the LED and the batteries. It is best to follow the directions from the flashlight manufacturer about which batteries should be used.
You should be just fine with the single 18650 (3.7v vs the 6v of 4xaaa), and much happier with it's longevity, and the fact that it's rechargeable.
IF the light has an electronic current regulator (which is likely) , it'll accept the 3.7v just fine (the LED emitter is likely rated 3.3v or less but current limited).
Some of these type flashlights even come with a plastic sleeve to better center the 18650 when using it instead of the aaa pack.
I love the 18650 cells; have tons of them onhand from disassembling old/bad laptop batteries (that usually only have a single failed cell and 3, 5, or 7 other good ones).
The flashlight could very well be brighter with the 18650, as typical aaa's cannot provide a lot of current, and the 18650 can certainly deliver plenty of current for a led emitter whilst maintaining it's full 3.7v output.
I have a ton of the wf-502 flashlights as well - cheap, almost indestructible, last forever, and plenty bright with a single 18650 battery. I've got ones in green, red, and ultraviolet as well.
All depends on the flashlight design. The more expensive LED flashlights incorporate current limiters, but the average cheap flashlight may not always have them. If there isn't a current limiter in the flashlight, the LED will run brighter and hotter, which in turn reduces the LED's life span. You can do the same to an incandescent lightbulb by overpowering it (like what happens during a power surge after a power outage). It is always wise to follow the flashlight manufacturer's advice. The problem may not be the LED itself being overpowered, but the heat increase being transferred to the lithium batteries.
Hard to tell what caused this flashlight to blow. Maybe a defect? I do know that a short circuit could cause any lithium or alkaline battery to blow up: https://www.youtube.com/watch?v=cYrqHK5b8U0
Ok I'm the OP and the tactical flashlight I been talking about from harbor freight that calls for 4 aaa's but apparently works with 1 - 18650 recahrageable li-on too is being sold under different names and some say to use 18650 battery not aaa. Heres a youtube links to the flashlight that takes the 18650 and it looks virtually same as my harbor freight light. 2nd video is my quantum 588 harbor freight light that uses aaa's which is on sale now for $5 limited stock since they now have 590 flashight selling for $14 and looks identical to my 588. My light doesnt come with the palstic sleeve for 18650 battery shown in first vid and has 4 modes intead of 5 but otherwise looks same.
edit: 3rd link is my harbor freight light that calls for aaa, 4th link is walmart same looking light takes 1 - 18650 battery sells for $12 without battery.
Just bought a harbor freight tactical flashight that runs on 4 aaa batteries and stuck a 18650 battery in it and it works much to my surprise. The flashlight isnt made to use 18650 battery so i want to know if it's likely to damage the light or not. Because i was thinking of using the 18650 to see if run time would be longer than 4 aaa eneloop rechargeables which last about 1 hr or so.
Does your flashlight have a little cylinder that you put the 4 AAAs in? You popped that out and put in the 18650? Funny thing is that I JUST received delivery from Amazon yesterday a couple of tactical flashlights that allow the use of either 3 AAAs or on 18650. Both are safe to use. However, with yours being from Harbor Freight (yuck) it may not be. Especially if the directions say ONLY to use AAAs.
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