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  1. #1
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    Found a buch of li-on batteries at work

    So I have access to a few lli-on batteries i found at work.

    They are an 8.4v pack 4400mah.

    Few questions i have are.

    Charging these, is this a protected circut built in?


    What charger would work for this set up? ( i am assuming they are a balanced setup)

    If not I have the unit that these fit into. It could be used as the charger.

    Any difference then the 14.4v pack i run ?(drivers will accept both

    Hoping to get my next build going if can ever find the money. These would save a few bucks and no need for a fancey holder as they already come sealed up.

    Thanks

  2. #2
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    Forgot topost other pic. For hook up on these, I am not getting full voltage from the factory connections. Only getting 6.7 but when I connect to the main + and - on the board I get 7.4v. I am assumin this is to do with the balanced charging.

    When hooking up a driver would i leave the factory style connections alone and use the main direct to the batteries?

    Thanks

  3. #3
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    nice find! I've salvaged a lot of li-ion battery packs and it sounds like you've done the first thing, which is to check the cell voltages. Now you need to charge them up and see if they hold their charge (voltage doesn't drop over time) and if they have any useable capacity. The easiest way to do that is with a hobby charger, but it doesn't sound like you have one. If not, you can split the pack into parallel pairs (voltage between 3 and 4.2V) and charge them on a cheap li-ion charger ($6-7 from eBay, DX.com, Fasttech etc). Then you'll have to find some way of comparing their discharge time vs. a known source.

    I would do all of that before thinking about putting them in a light battery pack. I have done it before, but you just need to know what you have before you use it so that you don't get stranded in the woods without a light.

    That board in the photo is a PCB, but it's quite specific for that pack and it's use. It's also not balance charged (the extra wires are for cell voltage sensing). If you want to use a PCB in a new pack with these cells, I'd look into buying one that suits the application. They're not that expensive.

  4. #4
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    They come from a cable modem I was thinking I will use the original device to do the charging. They also keep a constant charge as needed. Normally these are installed for years at a time. No need for external charging now. I will hook it up to my current lights as the dx driver will work on 8.4v.

    So as for the main connection, I assume i should solder my leads to the main +and - on the board and not use the factory connection? Wasnt getting full voltage from the factory connection, I guess this is due to the cell monitoring?

    There is 5 connections.

    Thanks for takig the time.

  5. #5
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    They are sanyo cells. Btw

  6. #6
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    Quote Originally Posted by machine4321 View Post
    They come from a cable modem I was thinking I will use the original device to do the charging.
    Because that board is specific to the cable modem device it is difficult to know what all its functions are. Charging with the original charger seems OK but little is know about it too. If the purpose of the batteries are to power the modem through line power loss, you may find that the charger is not really designed to charge with any speed. It may be more of a "battery tender".


    Quote Originally Posted by machine4321 View Post
    So as for the main connection, I assume i should solder my leads to the main +and - on the board and not use the factory connection? Wasnt getting full voltage from the factory connection, I guess this is due to the cell monitoring?

    There is 5 connections.
    If you connect your light to the main + and - connections it will work as long as your driver and LED setup are compatible with 8.4V. The cells are not protected so you'll need to be careful to not over discharge the pack. Since you say that the output of the pack through the PCB is only 6.7V I suspect that there is a voltage regulator on the board.

    If it were me, I'd ditch the OEM board and charger. Get an 8.4V protection PCB from someone like Batteryspace to build into the pack and a hobby charger. Then you get good charging, over charge protection and over discharge protection and balancing if you add the connector.
    Last edited by Vancbiker; 09-27-2013 at 12:38 PM. Reason: add detail

  7. #7
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    That sounds like the way to go. Dont need fires to light my night rides.

  8. #8
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    ditto what he ^ said

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