How good are laptop 18650 batteries for basic use?

Mystery · Nov 29, 2020

Hi all, new user here. Coming from BLF forums.
I pulled 18650 batteries from two laptop batteries.
One was from old Dell laptop. It has 2800mah LGABC21865 batteries.

Another was from new Toshiba laptop. The battery was extra ordered with the laptop but never used.
It has 2600mah Samsung ICR18650-26F batteries.

They may not work for high drain flashlights but I only have basic lights like Convoy S2+.
Should I be okay with these or need to buy proper Samsung 30Q or similar?

WalkIntoTheLight · Nov 29, 2020

They're fine. I have some 26F cells, and they work just fine in my Convoys. Max current draw in the Convoy is 2800mA (assuming you bought it with the max config), and that's well within the 5200mA max drain of those cells.

Even in lights with a FET driver (such as the BLF A6), they work fine. They don't give quite as high output as a 30Q, but they're still pretty good. With a FET driver, their inherent voltage sag will limit current to under 4 amps.

Mystery · Nov 29, 2020

WalkIntoTheLight said:
They're fine. I have some 26F cells, and they work just fine in my Convoys. Max current draw in the Convoy is 2800mA (assuming you bought it with the max config), and that's well within the 5200mA max drain of those cells.

Even in lights with a FET driver (such as the BLF A6), they work fine. They don't give quite as high output as a 30Q, but they're still pretty good. With a FET driver, their inherent voltage sag will limit current to under 4 amps.

I don't have a charger that analyzes battery.
I checked with multimeter and the volt is good.
Can I also check the resistance with a multimeter to make sure they are good?

adamlau · Nov 30, 2020

Mystery said:
Can I also check the resistance with a multimeter to make sure they are good?

Internal impedance/resistance of batteries

WalkIntoTheLight · Nov 30, 2020

Mystery said:
I don't have a charger that analyzes battery.
I checked with multimeter and the volt is good.
Can I also check the resistance with a multimeter to make sure they are good?

Not easily at all. To check resistance, just compare them in a light with a FET driver, against a good battery. Or, don't bother, because if the resistance is too high to use in your Convoy, you'll know it. (Poor output, and/or short run-times.)

Mystery · Nov 30, 2020

adamlau said:
Internal impedance/resistance of batteries

Thanks.
Looks like it won't work with my multimeter.
It only goes down to 200 ohms.

WalkIntoTheLight said:
Not easily at all. To check resistance, just compare them in a light with a FET driver, against a good battery. Or, don't bother, because if the resistance is too high to use in your Convoy, you'll know it. (Poor output, and/or short run-times.)

I never timed it as I only use it around the house few minutes at a time.
Hopefully, after this stupid virus thing is over and weather warms up, I can go camping and use them for longer times.

aau007 · Dec 2, 2020

you can use a brute force and not very scientific method if you did not do some prep work.

charge up all the batteries and put them in the intended use flashlight. Leave light on high and start clocking it until light goes out. Then throw away those that does not last long enough.

Because those laptop batteries are all flattop, some light may require you to put a dab of solder on the +.

How good are laptop 18650 batteries for basic use?

Mystery

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WalkIntoTheLight

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Mystery

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adamlau

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WalkIntoTheLight

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Mystery

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aau007

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