PCB Battery overdischarge protection. Where can I buy one?- Mtbr.com
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  1. #1
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    PCB Battery overdischarge protection. Where can I buy one?

    Hi,
    Im looking for a battery overdicharge protection PCB circuit to put on a 7.4V LiPo. It needs to have a max current draw of about 7A and no minimum. I cant seam to find one but Im sure they are somewhere.

    The only ones that I can find have a discharge protection to 2.3V which is wierd as LiPos shouldnt be discharged to below 2.8 - 3V and they wont recover if they go below 2.5V

    Anyone know where I can find one? Preferably somewhere that the postage to the UK isnt going to cost more than the board.

    Thanks

  2. #2
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    hi james, ..... here ya go
    ............7A. ???? jeez, what you running?

    http://stores.shop.ebay.co.uk/LEDSEE-electronics

    http://stores.shop.ebay.co.uk/LEDSEE...34Q2ec0Q2em322
    ...Scun.thorpe, UK

  3. #3
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    Great find Hendo, just what I've been searching for(but never found)

  4. #4
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    Thanks Hendo but the 7.2V PCB has a max discharge of 3A. I need 6A for a dual P7.

    Got any more?

  5. #5
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    Hi James,
    Ive got a few 2S 5A rated ones 4 each inc p & p & paypal

    Electric performance

    * Overcharge Protection voltage for single cell: 4.35V +/- 0.025V
    * Overdischarge Protection voltage for single cell: 2.3V +/-0.1V
    * Overcurrent detection Protection <= 5 A +/-1A
    * Short circuit Protection.

    Email me if youre interested
    I'm in the UK too

    Likewise, what do you want to run 7A min for?

  6. #6
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    james, your dual P7 with a battery voltage in>7.5+v will pull less than 3Amps
    maybe you`r adding the 2.8A + 2.8A current??
    ...Scun.thorpe, UK

  7. #7
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    Ok, well my setup is slightly different. Maybe Ive worked it out wrong but here goes...

    Its a project I started a while ago when the P7 first started to appear and I bought most of the parts and did the machining for the housing but never got round to finishing due to no time.
    I've got 2xP7 each driven independently by a KD P7 driver. The idea being that I can control each independently from a dual switch near my thumb as one will be a throw and one a flood.

    Each one has a Vf of 3.6V so in series 7.2V, 2.8A however if you use a 7.4V battery its lower limit is about 5.6V so you will never get the full runtime. So if I run them in parallel then you will only need 3.7V from the battery and you will see the full runtime but you pull 6A from the battery?

    Or have I missed something?

  8. #8
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    Having just gone back and read the KD site, at 7.2V input the driver only pulls 1.6A and at 5.5V it pulls 2A so the max I will need is 4A

    Must remember to check ideas that I have late at night!! + =

  9. #9
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    @smudge: Having recalculated , assuming Im now correct I would be intereseted in a PCB from you. 1 for now but maybe another one later if I need another pack. but can you please explain something to me.

    From everything I have read and to my knowledge (which I admit is limited) from using them for RC helicopters, LiPos, will not recover if they are discharged below 2.5V per cell and its recommended not to go below 2.8-3V to maintain a high cycle life. LiPos are more sensative to charging than LiIons and they are not meant to be charged to more than 4.2V per cell and I have seen some pretty explosive videos of overdischarged batteries and overcharging them and puffing before exploding!!

    http://www.youtube.com/watch?v=SQ0SNESIkWk

    How come then that all the PCB protection boards that I have seen only protect from 2.3V to 4.35V???

    The RC protection circuits (they beep/ flash loudly when you get close to low voltage) are all set at 2.8-3V. Are the RC guys just over delicate as they need to pull 20C from the battery or are the DIY lights just a bit close to line??

  10. #10
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    James,

    Mail me youre address and i'll pop one in the post to you. Just drop a few quid in a local charity box and that will cover it.

  11. #11
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    e-mail sent. Thanks

    Are you sure that you dont want me to donate to the Smudge Beer Charity?

    Does anyone have an answer to my voltage useage question though?

  12. #12
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    Does anyone have an answer to my voltage usage question though?
    ............ which one?
    ...Scun.thorpe, UK

  13. #13
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    question is in post #9!!!!!!!!!!!!
    Last edited by Whitedog1; 05-27-2009 at 03:00 AM.

  14. #14
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    The question in post #9 about the voltage that you should allow LiPos to be discharged and charged to.

    Is it safe to go down to 2.3V becuase from everything I can find 2.8-3V is the minimum.

    Sorry there are so many questions but like to understand "why" and Im a mechanical engineer not electronic so I could calculate the strength of the housing or the heat flow patterns but it takes a little longer work out the black magics of electricity bit
    Last edited by james266; 05-27-2009 at 02:49 AM.

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