Low Temperature Li-Ion 18650 Test- Mtbr.com
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  1. #1
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    Low Temperature Li-Ion 18650 Test

    I used a Bright Eyes light advertised @1,200 lumens and it's 4,400 mAh Li-Ion 2S-2P 8.4V battery pack. The Li-Ion cells were unmarked.

    These 18650 Li-Ion cells were allegedly rated 2,200 mAh. The Bright Eyes light kit package was sealed until opened about 2 weeks before this test. The battery pack was used about 6 times with approximately 4 hours total use.

    If the battery pack was outside for more than 30 minutes @20F, there was less than 12 minutes run time on high before the battery pack shutdown.

    Test #1

    The battery pack was fully charged.

    The battery pack temperature was 80F

    I placed the fully charged battery pack in a 4.9F freezer with Bright Eyes light outside of the freezer.

    I turned the Bright Eyes light on high.

    The battery voltage steadily declined until low voltage shutdown occurred @5.80 VDC @0 hours, 22 minutes.

    I allowed the battery pack to warm to 80F.

    I turned the Bright Eyes light on high.

    The battery voltage steadily declined until low voltage shutdown occurred @6.14 VDC @0 hours, 56 minutes.

    The no load voltage was 7.58 VDC.

    The total run time cold and warm was 1 hour, 18 minutes.

    +++++++++++++++

    Test #2

    I disassembled a dead aftermarket battery pack from a Mac Laptop computer.Four of the six cells were still good and had some charge left in them. The battery pack was at least 4 years old. The 2,600 mAh 18650 cells were marked: ASO FK1K031EG 814793 SZN with a sea foam green sleeve.

    I removed the battery protection circuit from the Bright Eyes battery pack and wired it to these recovered batteries in a 2S2P configuration.

    The battery pack was fully charged.

    The battery pack temperature was 80F

    I placed the fully charged battery pack in a 4.9F freezer with the Bright Eyes light outside of the freezer.

    I turned the Bright Eyes light on high.

    The battery voltage steadily declined until it reached 6.10 VDC @1 hour, 23 minutes.

    The battery voltage then began to rise until it peaked at 6.43 VDC @1 hour, 56 Minutes.

    The battery voltage steadily declined until low voltage shutdown occurred @6.01 VDC @2 hours, 58 minutes.

    The no load voltage was 6.83 VDC.

    I removed the battery pack from the freezer and I measured the battery case temperature @41F.

    Total run time 2 hour, 58 minutes.

    I did not perform an additional test after the batteries were warmed back to 80 degrees.

    I believe that the battery voltage rise was occurring because the internal resistance of the battery was rising significantly and causing heat to dissipate inside the battery, which allowed the battery to output voltage longer.

    These tests were performed with generic Li-Ion batteries. There are some Li-Ion cells that are formulated to operate at low temperatures.

    Nitecore makes low temp Li-Ion cells:

    http://flashlight.nitecore.com/product/nl1829lthp

    http://flashlight.nitecore.com/product/nl1829ltp

    I'm sure that there are other low temp Li-Ion cells out there.

    Scott Novak

  2. #2
    RAKC Industries
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    Scott

    Nice work, just goes to show if its a cheap light its got cheap batteries. No way around it. Bright Eyes is no exception.

    I was surprised to see the laptop batteries last as long as they did, means that light is not near as bright as claimed.

    Sent from my SM-G950U using Tapatalk
    Life on a bike doesn't begin till the sun goes down.


  3. #3
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    @RAKC Ind,

    Can you say 1,200 Faux Lumens?

    I thought you could.

    Maybe I should buy some of those "12,000 mAh" Li-Ion cells to go with it.

    I bought the light dirt cheap on craigslist, so it's no great loss. I'd need about 4 of these lights to give me the coverage and light intensity that I want. I figure that's probably about 2,000 real lumens.

    I may do some additional testing with the battery packs starting out cold.

    Scott Novak

  4. #4
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    Quote Originally Posted by Scott Novak View Post
    I used a Bright Eyes light advertised @1,200 lumens and it's 4,400 mAh Li-Ion 2S-2P 8.4V battery pack. The Li-Ion cells were unmarked.

    These 18650 Li-Ion cells were allegedly rated 2,200 mAh. The Bright Eyes light kit package was sealed until opened about 2 weeks before this test. The battery pack was used about 6 times with approximately 4 hours total use.

    If the battery pack was outside for more than 30 minutes @20F, there was less than 12 minutes run time on high before the battery pack shutdown...
    Apparently you got a crap battery with the B-eyes light. Likely recycled cells that are only in the 700-1200mAh range. Even cold any battery should have better run time.

    I can't help but wonder what the voltage indicators on the lamp were doing since most of these cheap Chinese type lamps have some kind of voltage indicators. It's possible of course that you might have gotten better run time ( cold ) if you had powered the lamp down to it's mid-mode. . Anyway, if this was a low voltage issue with the battery indicators on the lamp should have been in the red.

    I should also note that you didn't mention if the lamp head had any fan blowing air on it while doing the test. If not there's always the chance that perhaps the lamp turned off due to thermal shut-down. Heck, even with a fan blowing air there is still a chance ( if set on high ) that the lamp may still turn off due to thermal protection circuit turning off the lamp. Real important to know what the voltage indicators were telling you before you start blaming the battery. Of course since you also tested using another battery it's clear that the B-eyes battery was crap.

  5. #5
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    The light was laying sideways on the kitchen counter top with no air flowing and the ambient temperature was 80F.

    The light is specified to be able to run at 5 VDC. I ignored the voltage indicator on the light as I had voltmeter probes attached directly to the cell terminals inside the freezer.

    I know for certain that it was the under voltage circuit that tripped because there was no voltage present on the output plug of the battery pack immediately after the shutdown. The no load voltage was measured directly across the battery terminals thereby bypassing the protection circuit.

    I have no interest in testing the light in the low setting as the light is insufficient for anything but allowing other people to see you.

    I had previously run the Bright Eyes battery pack inside the apartment to test it and it ran the light on high for almost 2-1/2 hours before the under voltage circuit tripped. It's battery chemistry is just very poor for cold weather.

    A battery manufacturer can make a battery with a higher capacity if they don't worry about low temperature operation. I'm sure that these batteries were made by a company only worried about sales and not real world performance like reputable manufacturers do.

    I should probably do a test in the apartment to see how long the recycled laptop cells will run with the light on high.

    At some point I'll open the light and take some LED current and voltage measurements. But I've first got to ride up to my storage locker and dig out my current shunts. But I don't have much incentive to ride 34 miles round trip in the cold.

    Scott Novak

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