DIY 2 Cell Helmet Battery- Mtbr.com
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  1. #1
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    DIY 2 Cell Helmet Battery

    I'm after a two cell battery for to mount on my helmet for my BT21 and I was thinking of making my own.

    I was looking at using one of these holders for 2 x 18650 cells.

    DIY 2 Cell Helmet Battery-1279500-3.jpg
    Fasttech Link here

    The holder comes with a protection circuit and I was then going to load it up with two unprotected Panasonic cells, fit a length of cable then heat shrink it.

    A few questions:
    - Does what I'm planning to do make sense?
    - Is there anything that I should be cautious of?
    - Where can I get a decent 20awg lead from (I've got 22awg)?
    - The description says 7.4V but the battery on my light is 8.4V, is this an issue or will I get 8.4V in reality?

  2. #2
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    Quote Originally Posted by gravitykid View Post
    I'm after a two cell battery for to mount on my helmet for my BT21 and I was thinking of making my own.

    I was looking at using one of these holders for 2 x 18650 cells.

    Click image for larger version. 

Name:	1279500-3.jpg 
Views:	246 
Size:	41.4 KB 
ID:	1031069
    Fasttech Link here

    The holder comes with a protection circuit and I was then going to load it up with two unprotected Panasonic cells, fit a length of cable then heat shrink it.

    A few questions:
    - Does what I'm planning to do make sense?
    - Is there anything that I should be cautious of?
    - Where can I get a decent 20awg lead from (I've got 22awg)?
    - The description says 7.4V but the battery on my light is 8.4V, is this an issue or will I get 8.4V in reality?

    it will work fine. I did that for a while. However I still use an extension and put in my jersey pocket.

    I use the DX magic shine extensions or y cables to get thicker wires.

    the cells are 3.7 volts (4.2 on full charge) to you get 7.4V. It ends up getting to 8.4 on full charge. for a 2SXP configuration.

    I would shrink wrap and plastidip the ends to water proof.

    I went to building soldered 2 cell packs as they are a little smaller and neater.

  3. #3
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    DIY 2 Cell Helmet Battery-imageuploadedbytapatalk1448395102.054274.jpg

    Here you can see the finished pack for your plan. And then vs 2 cell soldered pack. With your option you can always pull cells out to charge them for balancing occasionally.

  4. #4
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    Quote Originally Posted by ljracer View Post
    Click image for larger version. 

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    Here you can see the finished pack for your plan. And then vs 2 cell soldered pack. With your option you can always pull cells out to charge them for balancing occasionally.
    Thanks, that's great information.
    Looking at your photo I definitely want to go down the soldered route, it's a much neater solution.
    Where do you get your protection circuits from? I've seen some on AliExpress and eBay that look similar to the ones in your picture.

  5. #5
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    Look here: http://forums.mtbr.com/lights-night-...gb-982688.html

    Some people built packs using protection modules from "hunk lee" on ebay.

  6. #6
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    Quote Originally Posted by nathan89 View Post
    Look here: http://forums.mtbr.com/lights-night-...gb-982688.html

    Some people built packs using protection modules from "hunk lee" on ebay.
    I get 2 hrs on my Gloworm X2 with a HunkLee 2 cell in a magicshine velcro case. Dipped the 2cell in Plastidip to make it waterproof. Performix 12213 Plasti Dip Black

    Post pics of your helmet/light setup.- Mtbr.com

  7. #7
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    I got my pcbs from Hunk_lee on ebay. His store is fma battery.

    Right now gearbest has ncr18650b for 4.24 each.

    I picked up nickel strips off ebay for connections. Search the threads here for technique if you want to make your own.

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