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  1. #1
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    18650 Edit: 2s1p Not pulling enough power

    I have a Gemini Olympia, which I've used for several years on my MTB and roadie. The 4 cell battery back was sort of excessive for road riding, so I built a battery pack using 2 Panasonic 3400mAh NCR18650B. It works, but it only powers a single LED and button flashes red showing low power. I can only assume this is because the 2 cells are not able to keep up with the power draw. Anybody have any suggestions for me? I was thinking maybe I should just get a cheap light that has a lower power requirement? FYI this is what I used to built the battery back: http://www.batteryspace.com/Battery-holder-Li-Ion-18650-Battery-Holder-2S1P-With-2.6-long-20AWG.aspx
    Last edited by andrewfelix; 02-18-2017 at 11:21 PM.

  2. #2
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    You can't use a 1s 4.2v system to power most mountain bike lights. The minimum is 2s1p 8.4V. Your basically supplying half the voltage the light needs to operate.

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  3. #3
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    Whoops, I meant to say 2s1p

  4. #4
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    Hopefully the OP just linked the wrong holder from batteryspace. This would be the correct holder to use with an Olympia....

    Battery holder: Li-Ion 18650 Battery Holder (2S1P) With 2.6" long 20AWG & PCB
    GoPro adapters for bike lights http://www.pacifier.com/~kevinb/index.html

  5. #5
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    Yep @vancbiker quite right.

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  6. #6
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    They should be able to run the light fine, does the light work OK with the stock pack?

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  7. #7
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    Yeh the light works fine otherwise. I thought I read somewhere that smaller packs can't power the higher setting on some lights.

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  8. #8
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    Quote Originally Posted by andrewfelix View Post
    Yeh the light works fine otherwise. I thought I read somewhere that smaller packs can't power the higher setting on some lights.

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    Can you check your voltage?

  9. #9
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    I've run lights that size and bigger off a 2 cell pack. Won't sustain high for very long though.

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  10. #10
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    Quote Originally Posted by andrewfelix View Post
    I have a Gemini Olympia, which I've used for several years on my MTB and roadie. The 4 cell battery back was sort of excessive for road riding, so I built a battery pack using 2 Panasonic 3400mAh NCR18650B. It works, but it only powers a single LED and button flashes red showing low power. I can only assume this is because the 2 cells are not able to keep up with the power draw. Anybody have any suggestions for me? I was thinking maybe I should just get a cheap light that has a lower power requirement? FYI this is what I used to built the battery back: http://www.batteryspace.com/Battery-holder-Li-Ion-18650-Battery-Holder-2S1P-With-2.6-long-20AWG.aspx
    Keep in mind the voltage indicators ( for the Olympia ) are set at points that relate mostly to a much larger battery. I'm sure the Olympia must have more voltage drops since it's using three LED's. I wouldn't worry about the red indicator. It's gonna be on your head so you don't see it anyway. The biggest issue is you need to program the modes to lower outputs if you are using two cell batteries OR be sure to only use the highest output when really needed or else don't be surprised to see the lamp power down on it's own when it senses the available voltage level drop.

    Personally I've run the Olympia I have on the helmet but when I do so it's only when using a good 4-cell battery pack ( in my H-backpack ). If I choose I can use a Gemini Duo on the lid and use a two cell mounted on the helmet. Duo works great with a 2-cell and seems to have more punch than than the Olympia ( with two spot optics ) but of course the Olympia supplies a much over all wider spot and beam pattern. Regardless of the lamp being used you just need to keep in mind when using a two cell battery that it's best to not use the higher power levels a lot if you want any kind of decent run time.

    When using the Duo/2-cell I'll generally run the lamp at half power for most of the ride ( ~600 lumen ). Doing that I can get through most of my typical 2-3hr night rides without needing to worry about the 2-cell running out of juice. Now if I think I'm doing a ride with a 1/2 hr long, high speed downhill run I'll pack a second 2-cell and switch packs just before the long drop and then run the max output.

  11. #11
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    Quote Originally Posted by Cat-man-do View Post
    Keep in mind the voltage indicators ( for the Olympia ) are set at points that relate mostly to a much larger battery. I'm sure the Olympia must have more voltage drops since it's using three LED's. I wouldn't worry about the red indicator. It's gonna be on your head so you don't see it anyway. The biggest issue is you need to program the modes to lower outputs if you are using two cell batteries OR be sure to only use the highest output when really needed or else don't be surprised to see the lamp power down on it's own when it senses the available voltage level drop.

    Personally I've run the Olympia I have on the helmet but when I do so it's only when using a good 4-cell battery pack ( in my H-backpack ). If I choose I can use a Gemini Duo on the lid and use a two cell mounted on the helmet. Duo works great with a 2-cell and seems to have more punch than than the Olympia ( with two spot optics ) but of course the Olympia supplies a much over all wider spot and beam pattern. Regardless of the lamp being used you just need to keep in mind when using a two cell battery that it's best to not use the higher power levels a lot if you want any kind of decent run time.

    When using the Duo/2-cell I'll generally run the lamp at half power for most of the ride ( ~600 lumen ). Doing that I can get through most of my typical 2-3hr night rides without needing to worry about the 2-cell running out of juice. Now if I think I'm doing a ride with a 1/2 hr long, high speed downhill run I'll pack a second 2-cell and switch packs just before the long drop and then run the max output.
    Thankyou Cat-man-do! Helpful as always.

  12. #12
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    I'd also like to hear voltage measured off the newly built pack. Also, given a choice you should have used cells which have less voltage drop like Panny NCR18650GA or my favorite, the LG 18650MJ1 (which BTW I see Mtn Elec no longer stocks).

    -Garry

  13. #13
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    Quote Originally Posted by garrybunk View Post
    I'd also like to hear voltage measured off the newly built pack. Also, given a choice you should have used cells which have less voltage drop like Panny NCR18650GA or my favorite, the LG 18650MJ1 (which BTW I see Mtn Elec no longer stocks).

    -Garry

    Thanks Gary, I'll see if I can dig up a multimeter and measure it.

  14. #14
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    Quote Originally Posted by andrewfelix View Post
    Thanks Gary, I'll see if I can dig up a multimeter and measure it.

    Looks like I must have ordered the wrong part. It's only pulling 3.8v

    Back to the drawing board.

    Thanks all for your help.

  15. #15
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    So the begining was right, 1s2p. Just get the 2s1p version and your good to go.

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  16. #16
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    Yep, I'm an idiot. Correct part ordered.

  17. #17
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    Nah it happens to all of us. Won't admit how often I've done that, click buy on the wrong part....

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  18. #18
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    Or the time I connected a 4.2v light to an 8.4v pack just to have it go "poof!"

    -Garry

  19. #19
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    Soldered wires backwards on the solarstorm case, same result to a bt21 "poof" lol

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