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  1. #1
    mtbr member
    Reputation: drunkmonckey's Avatar
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    Jul 2006

    is it worth it to DIY battery pack?

    I am in the process of building some lights similar to achesalot and others with 3 seoul P4 led's: mtbr linky here and achesalot's site If you read this, thanks a lot for taking the time to give such good instructions (and of course for coming up with the original concept).
    Question: I assume the big appeal (at least it is for me) is the fun of DIY, to possibly have a superior lighting product, and to ulimately save $. Based on the latter, i was wondering if there are cheaper alternatives to purchasing a battery pack and charger for ~$80 seeing as I am spending less than that on the lighting system itself. Sorry if this is an ignorant noob question, but may end up building 5 if it turns out well for some helmet/bar setups for a few of us.
    I assume a DIY would optimally have 8 ~2200mAh Li-ion batteries, battery holder, wiring, and then for protection - pcb and maybe a polyswitch to prevent overdischarge and polarity mistakes? Is there a problem with doing a setup or is the cost of it still high enough that it is just better to buy an already sealed up pack? Dan at instructables made his own without the protection stuff I assume.
    Thx in advance for any advice you have. Oh, planning on using "bFlex" on this one, but may try out one of the recommended buckpucks on another build. These will provide some protection and will moderate output?

  2. #2
    mtbr member
    Join Date
    Nov 2005
    Thanks for the kind words.

    You might save a buck or two if you have a good, cheap source for the cells and PCB, but generally, you can't save much... especially, considering the time and effort of soldering and shrink-wrapping.

    Let's venture to and compare:
    8 x Li-Ion 18650, 3.7v, 2.2A cells w/tabs = 46.32
    2x PCB (one for each set of 4 cells) = 19.30
    So that comes to $65.62 before shrink wrap and solder.

    I see two different 14.8v, 4400ma, Li-Ion packs, pre-built with PCB for $59.99 each.

    So it looks to me like you can buy the pre-built packs cheaper (at all-battery anyway). I'm not %100 on how the PCB board is wired (but it looks like you need one ($9.95) for each set of 4 cells). I would not use Li-Ion w/o protection circuitry. Bad for batteries... possibly bad for you.

    The bFlex is great... although there is (for me) a certain appeal in a continuously dim-able 3021 buckpuck with external pot. The bFlex is smaller and will fit in small housings, and it has a super-configurable menu system of clicks, double-clicks, triple-clicks... now how do I get back to that mode I was in? I really do like the bFlex/nFlex but in practice, reaching up to the light on my head or handlebar and dialing in the brightness level with a pot is much easier than a series of clicks or long presses and cycling through modes to get what I want (especially while riding on twisty, bumpy trails one-handed).

    Good luck.
    - Allen

  3. #3
    mtbr member
    Reputation: drunkmonckey's Avatar
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    Jul 2006
    Thx a lot for the reply. Ya, doing the calculations on the batteries, it wasnt looking good for saving money on the pack, especially with the extra work and my lack of electronics knowledge. Guess I'll be ordering a pack or two today. Then I think all I will need is for everything to come in and I'll be set.
    Based on your comments, I may try one of the buckpucks you recommended on my next build and maybe use the bflex setup on the bars if I find I need to adjust it a lot. I didn't know how much harder it would be, so thought I would stick to what you used in ur cree instructions to reduce the chance of mistakes.
    Thanks again.

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