Newbie In Search Of Longer Run Times for Cygolite Turbo 740-
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  1. #1
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    Mar 2010

    Newbie In Search Of Longer Run Times for Cygolite Turbo 740

    Hey guys,

    I did a bit of searching but couldn't seem to find enough information to help a lighting newbie like me make any accurate conclusions. I have a Cygolite Turbo 740 that I am planning on running as my helmet light for hopefully two 24 hour solo races next season (never raced 24H solo before). I'm planning on getting a Magicshine setup for the bars and some additional batteries so I can make it through the night.

    Cygolite does sell a "740 Extra" 7.6v li-ion battery but the run time on high is 4.5 hours, it needs 7 hours to charge, and it is $100. I know heat can be a big issue with LED's, but would the light be operable with a higher voltage battery pack with a higher mAh? I was thinking of buying an extra magicshine style battery and soldering on a plug that would work with the turbo. Seems like I could get longer run times at about half the cost.

    The other option is that I have two Cygolite 3.8V packs from a mitycross. Is there any reason I couldn't run these with the Turbo 740? I realize the voltage is different and the run time would obviously be less, but I'm just just trying to figure out my options to generate enough run time to get through the night.

  2. #2
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    May 2011
    OK basics first.

    Generally speaking you need to use batteries in the voltage range the light is designed for. In your case the Turbo 740 runs on "7.6v" This is just a nominal voltage. The actual voltage range for li-ion batteries is 3.0-4.2v so 2 li-on in series is 6.0-8.4v. If you want to understand more, read Battery University confusion with voltages.

    Long story short, the mitycross batteries won't work, the "magicshine" might.

    There are two ways to get more capacity (1) use cells with a higher capacity & (2) use more cells in parallel.

    The standard battery with the turbo 740 is 2 li-ion cells in series - 2s1p. The 740 Extra battery gets greater capacity by adding an extra 2 cells - 2s2p. Again Battery University has a good article Serial and Parallel Battery Configurations.

    Many "magicshine" batteries use low quality cells, with a resulting low capacity.

    The best capacity batteries use Panasonic 3400 cells. They are not cheap though. Cheapest I have seen is Hunk Lee but (1) the battery needs to be waterproofed & (2) there are often shipping problems from Chine to the USA - not limited to this seller, all sellers have had problems at various times.

    Another way is to get a waterproof box like this & individual cells - eg fasttech

    Sourcing from a local seller will avoid shipping problems, but the price goes up. Not sure where you are located but one US seller is Action-LEDs

    You are already aware of the need to change plugs to suit.

    Other issues
    Brand name lights can do various things which means you have to use their batteries - eg ay-up have the driver in the battery pack, so if you want to run your own battery, you need to find & use a suitable driver. I don't know if cygolight do any of these things.

    If the problem is the charge time, you could use a hobby charger. Again you would need a plug.

  3. #3
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    Mar 2010
    Thanks for the links Bruce! The stuff I found googling was not helpful. I am planning on sourcing the Magicshine setup from Action-LEDs and upgrading the batteries to Samsung 2800mAh 18650 Li-ion cells that they offer. I've got a lot to learn but I'd be stoked to build my own battery.

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