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  1. #1
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    L&M ARC HID custom battery

    So I have this ARC light but I need a battery and charger. Has anyone used one from Batteryspace? I'm confused on how to handle the 3-wire on the original ARC with only the 2-wire packs. Can anyone shed some light on the wires that are needed so I can replace with new plugs.

    Thanks

  2. #2
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    Buddy of mine asked me this question just a month ago.

    If I recall correctly - the 3rd wire was only for interaction between the charger and the battery - not the battery and the light head. The 3rd lead is to a thermistor circuit for a safety cutoff if the pack gets too hot while charging.

    This circuit and the plugs on the L&M stuff being proprietary means either you fork over huge cash for the L&M replacement parts, or you dump your L&M charger and battery. In your case I think you don't have these, so no loss.

    If you wanted to swap out to a 11.1volt Lithium ion pack from Batteryspace or All-battery or whatever - you can, but you need to swap out the connector on your light head to something common (trail-tech, or the Magicshine connectors.)

  3. #3
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    Actually I'm going to copy/paste the email I sent my buddy - he's an Electrical Engineer, so I went a little technical on the burn time discussion, I pulled the L&M info from this manual - http://www.lightandmotion.com/bike/s...hts_manual.pdf :

    From my research, I'm still about 95% sure any 11.1v Lithium-Ion pack would work with your L&M HID light. If i could find a pic of one disassembled, this could be confirmed by checking if only 2 leads enter the light from the battery connector.

    Since I know you have an electrical background, I can break it down a little more:
    L&M's runtime quotes for the 9cell lithium battery were 5.5 hours burn on high - drawing 13.5watts.

    13.5w *5.5hr = 74.25w/hr battery. 74.25/11.1v=6689mah total battery capacity. Since the battery is 3 parallel groups of 3 batteries in series, 6689/3=2229mah per parallel pack. Which means those packs were made from ~2200 mah cells.
    Today's low-capacity lithiums are 2200 or 2400 mah - and the top of the heap are currently Panasonic's 3400mah. Anything claiming higher capacity is lying at this point. These batteries are also a lot better that handling higher current draw than the older batteries were.

    Running only a 3 cell pack made of the nice Panasonics (37.75 w/hr battery)- you would get 2.8hr of runtime, or 75% of what you would have gotten out of the original 6-cell pack.

    A cheap 6 cell pack ($55) made of 2200mah cells would be something like 3.6hrs runtime on high - at least the math says so.

    A 9 cell, 6600mah pack runs about $75.

    You will have to change connectors on your ARC - as the L&M plug is proprietary and not available for consumers. On all my homebrewed stuff these days, I'm using the Magicshine connectors - I buy a couple of $5 3' extension cords, and cut them to whatever length I need. They fit tight and are relatively watertight.

    A nice 6-cell pack made out of the Panasonics would outperform the original 9 cell. But the Panasonics are running about $16 per cell right now.

    Of course all of this still hinges on the light only needing a pos/neg connection to a battery of appropriate voltage.

  4. #4
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    This is what I was thinking for the wire as well... that it was for monitoring the charging cycle. I have not opened the light yet to see if there is even a third wire into the light head, but will probably do that tonight.
    Maybe someone else will chime in for confirm, but thanks for the extra info!

  5. #5
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    Why don't you email the tech department at Batteryspace? I just emailed last night asking for a different configuration of their 12.8v LiFePO4 water bottle battery (I need a 6.4v pack), and they responded very quickly that they would build the battery at the same price as the one they already advertise.

    For what it's worth... I'll end up with a 6.4v LiFePO4 water bottle battery with a 13.2 Ah rating at 27.2 oz weight.

  6. #6
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    Yeah - I see the pack you mention on their website - but batteryspace isn't going to be able to solve the problem of the L&M plugs being proprietary - they can't be had by consumers.

    OP doesn't have a battery or charger. We know he needs an 11.1v pack, that's not a mystery - it comes down to how much runtime he wants to determine what Mah pack he needs to buy.

    For the $95 your pack is costing you, the OP can buy a nice 11.1v Li-Ion and a Turnigy Accucell-6 ($35 from Hobbyking) charger to complete the setup he's already got.

  7. #7
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    delete: wrong thread.
    Last edited by adrenalnjunky; 01-16-2013 at 11:09 AM.

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