LiPo Battery use in Bike lights??- Mtbr.com
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  1. #1
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    LiPo Battery use in Bike lights??

    Why dont manufactures use LiPo Batteries for bike lights? They are lighter and can be made into any shape. I know they have a soft shell and need a hard case added but that doesn add much weight and most LiIon packs have hard cases anyway? The RC crowd uses them almost exclusively now.

    Does anyone use them for their DIY lights? If not why not?

  2. #2
    aka Chris
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    Ay-Up use LIPO batteries.
    The Novice's LED Light Building Blog

  3. #3

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    LiPos are more dangerous than Li-ions. They're also a newer technology. They completely outperform Li-ions though - better specific energy, better energy density, better power density, and better lifespan.

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    Exactly so why arnt more people using them?

    Ok the mainstream market will take time but the mainstream Remote Control market have already adopted it. What about the the DIY light builders from what I can tell most people are still using LiIon?

    I have built a dual P7 and am looking at getting a 2x5000mAh LiPo for 24!! Ok its probably a cheap copy that wont actually hold 5000mAh but for that price its a heck of a lot cheaper than Li-Ion, small and lighter!

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    Quote Originally Posted by james266
    Exactly so why arnt more people using them?

    Ok the mainstream market will take time but the mainstream Remote Control market have already adopted it. What about the the DIY light builders from what I can tell most people are still using LiIon?

    I have built a dual P7 and am looking at getting a 2x5000mAh LiPo for 24!! Ok its probably a cheap copy that wont actually hold 5000mAh but for that price its a heck of a lot cheaper than Li-Ion, small and lighter!
    Well - for commercial products people are worried about safety as there is more lawsuit potential. At least that'd be my guess. LiPos are also more sensitive - and just a little more scary. I don't blame people for staying away from them. Overdischarging a Li-Ion can damage it, but it won't blow up. Overdischarging a LiPo? That can have much more exciting results.

    I personally am using LiPos in my headlight project. (10 6.6Ah cells in series, because I'm a sick, sick individual)

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    I do. LiIon will explode, Lipo will swell and then kindle. I have shortcuted one for a second. It have swell a little, now it is on observation, but nothing happened for a month...
    They have been cheap and they work well. But when they expire I'll switch to LiFe.

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    Quote Originally Posted by frozen
    I do. LiIon will explode, Lipo will swell and then kindle. I have shortcuted one for a second. It have swell a little, now it is on observation, but nothing happened for a month...
    They have been cheap and they work well. But when they expire I'll switch to LiFe.
    I think Li-Ions only explode when overcharged or overheated (due to excess current draw). Is that wrong? I haven't done enough destructive testing on them to confirm.

    Why switch to LiFePo4? They have lower energy density and lower specific energy. Their only real advantage is if you need really discharge rates, which you don't really need for headlights unless you plan on going through your batteries in less than 12 minutes or so. (as LiPos are typically rated at about 2-5C continuous discharge, though I've seen some 10C cells). Oh, also I've heard that LiFePo4 cells can take more discharge cycles. So they have that going for them as well.

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    I have heard of LiPos exploding but only because of overcharging but if you have a good protection circuit and chrager there isnt any chance of that happening.

    The LiPos that are used for RC can easily go upto 20C constant discharge. The one Ive just ordered is 10C only because its the lowest C I could find.

    I need to try and find some kind of hard case for it now though. Was thinking of wrapping ally sheet around it.

  9. #9
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    Lipos are fine.

    I wouldn't worry about it, I've been using them for years without any problems.

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  11. #11
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    Quote Originally Posted by james266

    I need to try and find some kind of hard case for it now though. Was thinking of wrapping ally sheet around it.
    Unless you really need high C, it makes no sense to buy a lipo. If you need a high C battery, but are tempted to wrap it in an alloy sheet, that makes no sense because you can buy A123 (LiFe). For a low C application like bike lights, LiIon makes a lot of sense.

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    you don't need a lipo pack for a bike light. sure, they're VERY slightly lighter, but they're also more volatile, more finicky, etc.

    lipo's are only really an advantage for high current (20+amps usually), as was already mentioned, and even if you use that, it would probably be better to use A123 packs, which are higher discharge, and more resistant to blowing up.

    that said, if you already have some lipos, and know the dangers, and know how to handle them, there's no reason not to use them. I'll probably use some of mine for light projects at some point, but I'll stick with li-ion for any future projects.

  13. #13
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    Quote Originally Posted by Bryguy17
    lipo's are only really an advantage for high current (20+amps usually), as
    was already mentioned, and even if you use that, it would probably be better to use A123 packs, which are higher discharge, and more resistant to blowing up.
    That's what I run on some of my lights, a 5 series A123 pack of M1 cells (salvaged from a Dewalt battery). They do weigh more than an equivalent Lipo or Li-ion pack, but they are more forgiving when discharged too low and are a safer technology. I also use a Makita 18v LTX li-ion pack with a sandwich shoppe adapter plate. Both packs are pretty bulletproof.

  14. #14
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    Can you post a link to where you get your A123 from? I dont know much about them but they look interesting. Are they the same as LiFePo4?

    I use LiPos because I am familiar with them and can also use them in my RC heli but like has been mentioned are primarily for hi C applications. I do have a good charger which might not make it worth while if you use LiPos just for lights but I need it for my heli too

    I did recently find this cool post on making a hard case for LiPos that looks really easy and quite good. I might be trying it.

    http://forums.radiocontrolzone.com/s...d.php?t=247495

    The point about using LiPos though, IMO is that they are widley available online and very cheap compared to LiIons (for the cheap ones. High quality ones are VERY expensive). I know that the cheap ones arent as good but if you are carful with them they are cheap enough to be semi-disposable and they come ready made as a pack so there is less work involved.

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    I used one of these:

    https://www.nationwidetool.com/store...c9360-new.aspx

    It has ten A123 M1 sized cells in the pack.

    Here is another link of interest:

    http://www.slkelectronics.com/DeWalt/packs.htm

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    Quote Originally Posted by Bryguy17
    you don't need a lipo pack for a bike light. sure, they're VERY slightly lighter, but they're also more volatile, more finicky, etc.

    lipo's are only really an advantage for high current (20+amps usually), as was already mentioned, and even if you use that, it would probably be better to use A123 packs, which are higher discharge, and more resistant to blowing up.

    that said, if you already have some lipos, and know the dangers, and know how to handle them, there's no reason not to use them. I'll probably use some of mine for light projects at some point, but I'll stick with li-ion for any future projects.
    Huh - LiPos have the highest energy/mass and energy/volume of any of the standard battery technologies. In terms of energy/mass, they are about 25% better than Li-ion, 55% better than LiFePO4, 300% better than lead acid, and 250% better than NiMH. That is the big advantage of LiPos.

    The big advantage of LiFePO4 is the high discharge rate and the high charge cycles (around double that of most other battery technologies). But LiPos can still do typically 5C, some 10C, and some even as high as 20C. Remember that if you're discharging at 5C, you won't even get 12 minutes of battery life (<12 instead of 12 minutes due to the Peukert effect). I don't think many of us want our lights so bright/batteries so small that they last only 12 minutes. Thus I really don't see the power output of LiPos to be limiting for bicycle lights.

    The whole fire thing, however...

  17. #17
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    I don't think your weight numbers are quite right. If someone feels compelled to wrap their lipo in a hard case, any weight advantage goes away immediately. I only used them because I had them and I have very good lipo chargers. This same poster asked the identical question on candlepower forums, btw. Some interesting responses there.

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    Quote Originally Posted by unterhausen
    I don't think your weight numbers are quite right. If someone feels compelled to wrap their lipo in a hard case, any weight advantage goes away immediately. I only used them because I had them and I have very good lipo chargers. This same poster asked the identical question on candlepower forums, btw. Some interesting responses there.
    For work recently I did a study on battery technologies. Those numbers come from it. They were found by looking for the best cells available in each technology. They're accurate.

    You generally need a case around li-ions as well. I don't see that as a big advantage of li-ions. I mean - how many lights have you seen with the batteries out in the open?

  19. #19
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    Quote Originally Posted by uoficowboy
    Huh - LiPos have the highest energy/mass and energy/volume of any of the standard battery technologies. In terms of energy/mass, they are about 25% better than Li-ion, 55% better than LiFePO4, 300% better than lead acid, and 250% better than NiMH. That is the big advantage of LiPos.

    The big advantage of LiFePO4 is the high discharge rate and the high charge cycles (around double that of most other battery technologies). But LiPos can still do typically 5C, some 10C, and some even as high as 20C. Remember that if you're discharging at 5C, you won't even get 12 minutes of battery life (<12 instead of 12 minutes due to the Peukert effect). I don't think many of us want our lights so bright/batteries so small that they last only 12 minutes. Thus I really don't see the power output of LiPos to be limiting for bicycle lights.

    The whole fire thing, however...

    I'm not saying the Lipos may not be better on paper, but after assembling a pack, etc, you aren't looking at too big of a weight or performance advantage to offset the increased volatility of the cells.

    personally, I'll sacrifice some weight in order to have a lesser chance of dealing with a metal fire out on the trail, especially living in a fire-prone area. If I do use a lipo, it'll be safely housed in a metal cannister.

  20. #20
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    Quote Originally Posted by uoficowboy

    You generally need a case around li-ions as well. I don't see that as a big advantage of li-ions. I mean - how many lights have you seen with the batteries out in the open?
    Most DIYers using Li-ion seem to be quite happy with the cells wrapped in nothing more than shink wrap, with the pack thrown into a bag or a jersey pocket. I suspect that the reason that manufacturers tend to use fancier casings is more for looks and saleability rather than actual protection.

  21. #21
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    If you put a light weight casing on them it wouldnt add that much weight and pretty much all manufacturers put a case around their Li-Ion packs anyway.

    For DIY purposes, unless you are making an all in one I dont think that weight is much of an issue especially since LiPo packs are all square and LiIons can be built to certain shapes.

    My point about manufacturers using them is that they can be made into any shape. (I remember reading somewhere)

    As for DIY $ per mAh the middle of the range LiPos are much better than the middle of the range LiIons. For the ones Ive seen at least.
    Last edited by james266; 06-03-2009 at 06:41 AM.

  22. #22
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    I use LiPos 11 and 14v. However, my LiPo packs are heavier than DX LiIon cells of comparable capacity. I have also seen LiPos in hard cases on Ebay.

  23. #23
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    I've been using LiPos for years and like one of the above posters said I just chuck it in my jersey pocket with no further protection. I reckon the danger of them bursting into flames is greatly exagerated, I've had two puff up whilst charging on a cheap charger but since getting a better charger I haven't had any problems. There seems to be a lot of scaremongering going on.

  24. #24
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    Quote Originally Posted by Treadly
    There seems to be a lot of scaremongering going on.
    I think KipKay said it best

    http://www.youtube.com/watch?v=-DcpANRFrI4&feature=fvw

    But IMO the real danger is from this type of thing:

    http://www.youtube.com/watch?v=4OsBc...eature=related

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