Battery Pack Build for 2xMJ-808E-
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  1. #1
    mtbr member
    Join Date
    Apr 2010

    Battery Pack Build for 2xMJ-808E

    I was recently given a MJ-808E light-head by a friend who was upgrading. So now I have 2 light-heads and 1 4400mah battery. I would like to build a battery pack to power both heads with a Y-cable (1 w/ wide angle lens, 1 w/ standard optics).

    This will be my first battery pack build so I wan't to run it by you all first:

    I figure a 9300mah battery would give me around 3 run time hours with both lights on 9300 mah battery / 3amps (each light driven at 1.5 amps).

    Here is what I plan on using
    NCR18650A 3100mAh (Flat top) x 6
    fasttech for 39.9 ($6.65 x 6)

    Protection Circuit Module (PCM) with Equilibrium
    Function for 7.4V Li-Ion Battery Pack (20 Amp limit, PCM-L02S20-265)
    batteryspace - 15.95

    Trail-Tech Coaxis Female Lockable Connector with 4' Coil Cord
    batterysapce - 5.95

    So I will solder the batteries in a 2s3p confiruration which should give me 7.4v @9300mah

    1. Am I missing anything?
    2. Is the PCB I picked sufficient or could I go with a cheaper PCB and not worry about the balance charging function?
    3. Does anyone know where I can find NCR18650A 3100mAh with solder tabs?
    4. Will I still be able to use the stock Magicshine charger (from geomangear) to charge this battery pack?
    5. Weight is not really a problem so should I just go for a 2s4p build and get 12400mah for 4 hours run-time, the additional cost would only be $13 for 2 more batteries?

    Thanks for the help.
    Last edited by ubrv8; 03-15-2013 at 07:20 AM. Reason: typo

  2. #2
    mtbr member
    Join Date
    Jul 2007
    The PCB looks/seems fine for what you need. I don't know if the trailtech connectors are compatible with the MS light heads - buy yourself one of these y-connectors: Action-LED-Lights — Y-Cable that' will connect to MS heads to one MS battery. Then get one of these extensions: Action-LED-Lights — 1m Extension Cable & cut it up to use as the connector out of your new pack.

    If you have a BatteriesPlus store near you, they will weld you up a pack in the config you need for a couple of bucks, or less. they could just do tabs for you too, if needed. So far my local store hasn't charged me at all when I'm bringing in my own batteries.

    If you keep a pack at 2S - then the MS charger should be able to charge it to some degree - although I don't know if it has a capacity sensing function or not. For the money you're talking about spending on cells and what not, i'd spend another $30 and get a nice charger like a Turnigy Accucel or something. Turnigy Accucel-6 50W 6A Balancer/Charger w/ accessories Even charging at 6amps though, remember that is only 1/2C for a 12000mah pack. Would take 2-3 hours to charge. Something to consider if you're building one huge pack.

    If you want go 2S4P - I'd then suggest you do two 2S2P, one pack for each head - that way you have the most versatility. If you needed to you could loan one light to a buddy, or use as a helmet light if your current light dies. You could also then build a couple of y-harnesses that would allow you to Parallel the 2 packs if needed, or series for a 4S2P pack if you come up with some other light down the road. also gives you more options if a cell dies on you. Smaller packs are easier to charge and maintain, IMO.

  3. #3
    mtbr member
    Join Date
    Apr 2010
    Thanks for the feedback, I just placed an order for that charger and I think two 2s2p batteries sounds like a better option than one big battery. I will have to check out the local batteries plus to see what they can do for me, if not them I have an electrical engineer buddy who could probably solder everything up for me.


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