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.
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.)
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.
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!
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.
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.
Last edited by adrenalnjunky; 01-16-2013 at 12:09 PM.