Anyone using power tool batteries for homemade lights?- Mtbr.com
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  1. #1
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    Anyone using power tool batteries for homemade lights?

    After many years of spending far too much money on lights for 24 hour races, it occurred to me that there's a simple and proven system readily available in the form of power tool batteries.

    Waterproof, reliable chargers, and available over the counter at the hardware store at a decent price.

    The only problem is that most are 12 to 18 volts, so the lights would have to be capable of handling that.

    So 2 questions:

    1. If you have done this could you give us enough information to replicate it?

    2. Is there a simple hack so we can use those batteries with existing lights, e.g. put a resistor in the light cable etc, or do we need to build lights specially? (I was thinking of simply putting existing lights I have in series, i.e. running 2 sets of 7.4 volt lights in series with a 12 or 18 volt battery, but I don't want to risk frying them trying it out unless it is a reasonable thing to do.)

    I'm aware a proper mount and connection would have to be made for the battery, but that's pretty simple.

    I'm wanting to get powerful lights that will run for 18 hours minimum without needing to be recharged for our annual midwinter race (17-18 hours of darkness), so I figure start experimenting now for next year.
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  2. #2
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    Quote Originally Posted by Velobike View Post
    I'm wanting to get powerful lights that will run for 18 hours minimum without needing to be recharged for our annual midwinter race (17-18 hours of darkness), so I figure start experimenting now for next year.
    One or two of these might be better?
    http://www.kaidomain.com/product/details.S024616

  3. #3
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    Yes. I have considered them.

    What I like about the power tool batteries is that once I have made a suitable mount for the frame, they will just click in. No faffing with velcro, no taking off gloves to plug things together etc.

    But more important is the safety aspect.

    My experiences with generic Chinese batteries has not been good. If I use power tool batteries from a reputable company, e.g. Bosch, Makita etc, I don't have to worry about leaving them unattended during charging. After a couple of incidents friends have had with generic batteries I'm a bit wary.
    As little bike as possible, as silent as possible.
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  4. #4
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    Powertools cells are usually 30-40A discharge li-ions/li-fe with about 2000mAh. These days you can have four 3400/3700mAh Panasonic cells for $17. Probably not worth bothering with powertools cells unless you need to pull lot of amps.

  5. #5
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    Quote Originally Posted by MK96 View Post
    Powertools cells are usually 30-40A discharge li-ions/li-fe with about 2000mAh. These days you can have four 3400/3700mAh Panasonic cells for $17. Probably not worth bothering with powertools cells unless you need to pull lot of amps.
    I know. It's the trustworthiness of the powertool batteries and their charging system that appeals to me.

    I do have assorted generic Chinese battery packs, but I do not trust them based on the spectacular failures of others, ie I will not leave them charging unattended, so it becomes a huge hassle. They also seem to fail completely and randomly.

    It's the ready availability of reliable batteries that I can leave charging unattended that appeals to me, ie I'm looking for a battery that is widely available at the consumer level, and that is safe to leave charging unattended.

    I suppose my approach is that I am looking at my light problem from the battery angle first because that's where the problems lie, and then setting up a light system.
    As little bike as possible, as silent as possible.
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  6. #6
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    This is a battery pack that uses Panasonic cells inside. It is not a no-name brand. Very much similar to the cells you have in powertools and it has the protection circuit already. You might be over-engineering things using powertools batteries b/c the principle and cells used in tool packs and this pack from KD seller is very similar too. My two cents worth.

    Quote Originally Posted by znomit View Post
    One or two of these might be better?
    http://www.kaidomain.com/product/details.S024616
    Quote Originally Posted by Velobike View Post
    I know. It's the trustworthiness of the powertool batteries and their charging system that appeals to me.

    I do have assorted generic Chinese battery packs, but I do not trust them based on the spectacular failures of others, ie I will not leave them charging unattended, so it becomes a huge hassle. They also seem to fail completely and randomly.

    It's the ready availability of reliable batteries that I can leave charging unattended that appeals to me, ie I'm looking for a battery that is widely available at the consumer level, and that is safe to leave charging unattended.

    I suppose my approach is that I am looking at my light problem from the battery angle first because that's where the problems lie, and then setting up a light system.

  7. #7
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    Quote Originally Posted by MK96 View Post
    This is a battery pack that uses Panasonic cells inside. It is not a no-name brand. Very much similar to the cells you have in powertools and it has the protection circuit already. You might be over-engineering things using powertools batteries b/c the principle and cells used in tool packs and this pack from KD seller is very similar too. My two cents worth.
    It's a question of being able to trust the product. I've never heard of that online company, and its product is not readily available over the counter at my local hardware store in the UK. (I'm not talking about Panasonic ") ). I have spent thousands over the years on lights, and unless you pay through the nose, quality is variable.

    My point is that trustworthy batteries and charging systems are readily available at hardware stores at reasonable prices, so I'm looking at a way to take advantage of that.

    Their voltage and current aren't what I need, but that's something that can be sorted in the line between the battery and the light unit. That's the info I'm looking for - if anyone has done this before.
    As little bike as possible, as silent as possible.
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  8. #8
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    There are a lot of quality battery packs being made today. The tool batteries are heavy and aren't really what is needed on a bike. Why not just get a dyno hub and be done with it.

  9. #9
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    As said, biggest issue is size and voltage. Cordless batteries are INSANELY heavy.

    If you have spent a ton on lights that all have issues, stop buying the cheap Chinese crap off eBay.

    The packs linked there is threads about in the night riding sub. You may never have head of the site, but like 100% of everything made, you don't know about it till someone tells you
    Anyway can it be done, yes. But requires some decent electronics background.

    Is it worth it, you may think so now but adding 5lbs to your bike and having to carry several spare batteries to make it through the night makes it a VERY bad idea.

    Save yourself the hassle and heartache, just buy a quality set of lights instead of cheap junk.

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  10. #10
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    Quote Originally Posted by tigris99 View Post
    .....If you have spent a ton on lights that all have issues, stop buying the cheap Chinese crap off eBay.
    Not necessarily the OP's issue. When I started night riding/racing 15 or so years ago, I spent well over $1000 on 4 Niterider light sets. After 2 years I'd had to repair 2 of them. Keeping those going is what prompted me to start building my own lights.
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  11. #11
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    Quote Originally Posted by tigris99 View Post
    As said, biggest issue is size and voltage. Cordless batteries are INSANELY heavy.

    If you have spent a ton on lights that all have issues, stop buying the cheap Chinese crap off eBay...
    Lights I have bought:

    Ay-Up, Nite-Rider, Hope, USE Exposure, and they are/were good lights and that's what I have spent a lot of money on.

    However when the batteries fade, then the cost of replacing them is too high because by then the head unit is lacking in power compared to what is current.

    What's more there's no standard for connections, so if you want a replacement battery, there's little choice but to buy their proprietary model. That was ok when there was not much available in batteries. Not now.

    The cheap Chinese crap of eBay is exactly what I am trying to avoid because of the battery issues.

    As for the weight of the power tool batteries, the extra weight is minimal for the huge capacity IMO. It's basically a more bulletproof casing. Considering my early night riding was done with a motorbike lead acid battery and a small motorbike headlamp, I don't think the powertool batteries are too heavy.

    Quote Originally Posted by alphazz View Post
    There are a lot of quality battery packs being made today. The tool batteries are heavy and aren't really what is needed on a bike. Why not just get a dyno hub and be done with it.
    I've been using dynohubs for decades and I would use them if I was touring, but I don't need a permanent light on my mtb.

    If someone who has tried what I am proposing tells me it doesn't work, fair enough. Then I'll make my own battery pack and lights (which I did in the early days of LEDs)
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  12. #12
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    What I did was buy the cree knockoff from amazon. Something like the 6400 lumen. Not 6400 lumen, but a solid 1000. Definitely bright enough for trail riding and only $20. Battery sucks as expected, so I checked out spare remote control car batteries. With a $3 adapter plug, hooked right up. Still have to find someplace to store the battery on the bike, but that shouldn't be that big of a problem. I chuck mine in a stem bag with a couple spares. Normally I can ride for a good 5-6 hours off 3 batteries.

    Decent quality RC car batteries are readily available at any hobby store, inexpensive (sometimes), and have quality chargers. I still use NiMH batteries instead of LiPo because that's what my charger is for, but it's an old charger from about 12 years ago. New stuff will use LiPo batteries, have solid waterproof connectors, and are light weight.
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  13. #13
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    Quote Originally Posted by watts888 View Post
    ...Decent quality RC car batteries are readily available at any hobby store, inexpensive (sometimes), and have quality chargers. I still use NiMH batteries instead of LiPo because that's what my charger is for, but it's an old charger from about 12 years ago. New stuff will use LiPo batteries, have solid waterproof connectors, and are light weight.
    That's a good idea. I have looked at it though, and for short rides it is an answer.

    However I'm looking for an 18 hours burn and none of the batteries I saw in our local hobby shop had that sort of capacity. That solution would interest me otherwise, because the RC guys push the limits, so their gear is pretty well proven.
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  14. #14
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    If you can build packs and such your golden.

    Problem is cordless tool batteries are high voltage.

    You can get a circuit to reduce voltage but then you have an seperate unit that you have to self waterproof.

    But obviously you have the skills to do one simple thing. Buy the packs mentioned as they have top end Panasonic cells. Change connectors by robbing from old packs.

    Plasti-dip if your concerned about water making it in (heavy rains, possible submersions).

    Don't worry about current lights being outdated for a while. Current light offerings will only see improvements in the emitter outputs and those are fairly easy to change should u be concerned.

    Now if you want to go your route, and you have made your own light heads, then there are drivers out there that will run off those batteries no problem.

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  15. #15
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    I don't see value in using tool batteries. Same cells, but more weight, larger housings, and few even have their capacity listed.

    I think the best route would be to build packs to your specification. With a decent charger and cells you don't have to worry about leaving them alone. I've been using cells from dead laptop packs for 6 years now, and have had zero issues. Panasonic makes safe Li-ion batteries. Most modern LifePO4 batteries are incapable of overheating at charging voltages. The only batteries that were problematic for me were the cheap ones that came with some flashlights I've bought, and they just died, no overheating, because I don't use junk chargers.

    For 18 hours of powerful light, there are no tool batteries that will work. My Gloworm XS is rated for 2hrs of 2200lm powerful light with the 6800mah pack. Dropping that to 900lm (not powerful) bumps battery life to 8 hours. To get 18-24hour use out of a pack, I would need 12 cells. For truly powerful light, 24 cells. You are not going to find a tool battery with that kind of capacity that doesn't cost you $300 or more. Haven't even factored in capacity loss due to cold temps.

    Smaller packs mount easier on bikes, and demand less of their mounting system. If you're foing a circuit, do you want to carry your full capacity for every lap?

    5.5mm plugs are the norm for many bike lights, and you can add one to any light or battery you want. Sell off the overpriced proprietary battery, cut off the proprietary plug, and wire in a waterproof plug of your choice for all your lights and packs. Mix and match brands, won't matter.

    Regarding your suggestions on how to deal with differing voltages: Using a resistor is out, too much energy lost as heat. Using a voltage boost/buck is ok as long as the input and output voltages are reasonably close. The further the separation the more waste, and the more heat you have to manage with the converter.

    Do not try to use a boost/buck converter with non-DIY lights, it won't play nice with the boost/buck converter in the light head. Wire your own voltage transformer. Again, the closer the voltage, the less the loss.
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  16. #16
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    KD - Kaidomain has good stuff also. And the one linked here is such. I could buy Panasonic cells in my country, the trade off doing it is that I have to spend $22-25 for a single 18650 Panasonic cell. KD is not on my list of suspected low cost Chinese e-shops. Yes, they have some crappy stuff also, but you can read about the good ones here in forums ;-)

    Quote Originally Posted by znomit View Post
    One or two of these might be better?
    http://www.kaidomain.com/product/details.S024616
    Quote Originally Posted by Velobike View Post
    It's a question of being able to trust the product. I've never heard of that online company, and its product is not readily available over the counter at my local hardware store in the UK. (I'm not talking about Panasonic ") ). I have spent thousands over the years on lights, and unless you pay through the nose, quality is variable.

    My point is that trustworthy batteries and charging systems are readily available at hardware stores at reasonable prices, so I'm looking at a way to take advantage of that.

    Their voltage and current aren't what I need, but that's something that can be sorted in the line between the battery and the light unit. That's the info I'm looking for - if anyone has done this before.

  17. #17
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    Quote Originally Posted by Velobike View Post
    However I'm looking for an 18 hours burn and none of the batteries I saw in our local hobby shop had that sort of capacity.
    Almost no battery has that sort of capacity. Have to run them in huge parallel circuits to get 18 hours, or just bring spares. 18 hours is a long time to run lights. I think a Dyno hub is the best bet for that sort of time demand.
    "a hundred travel books isn't worth one real trip"

  18. #18
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    Here you go, looks like a decent build

    Kilo-Lumen bike headlight - All

    Just need to update to the latest and greatest LED's

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  19. #19
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    Not a bike light, but thought this one was an interesting use of 12V tool batteries





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  20. #20
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    Quote Originally Posted by scar View Post
    Not a bike light, but thought this one was an interesting use of 12V tool batteries
    Thanks. A bit more extreme than I was planning but instructive.
    As little bike as possible, as silent as possible.
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  21. #21
    Yeah!
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    Quote Originally Posted by scar View Post
    Not a bike light, but thought this one was an interesting use of 12V tool batteries





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    Had to exit, it was too annoying listening to him coyly pretend he's the first to do this.
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  22. #22
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    Lol can't agree with you more. Especially being at first I expected something ACTUALLY USEABLE. Wiring up an LED isn't hard if you understand positive, negative and operating voltage. At the very least (this part really annoyed me) spend $2 on a fraking switch.

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