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Question about how to wire this power

Discussion in 'Power Electronics' started by supraman215, Nov 5, 2018.

  1. supraman215

    supraman215

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    Nov 5, 2018
    I am making a battery and AC powered amplifier speaker. I'm stuck on this part of the circuit, pardon my horrific schematic.

    I have a battery protection circuit to control the over under charge on the 18650 li-ion batteries. Then I have a Smart charger that will control the voltage to charge the batteries.

    Here is the smart charger and PCM Iordered.
    ttps://goo.gl/qmGvHy

    Both the charger and the AMP will be powered by a 12v power supply.

    What I don't want is the 12v PS to power the PCM directly. Could I do this with diodes between the AMP and the PCM, I would also need them between the AMP and the smart charger?

    Even if that works how do I keep the power from the smart charger from powering the AMP?

    Do I need a switch of some kind? either a relay of some kind or manual switch?

    [​IMG]IMG_20181104_183659 by supraman215, on Flickr
     
  2. Bluejets

    Bluejets

    2,976
    577
    Oct 5, 2014
    So you want the amp to keep running on battery power when the mains supply fails?
    Is that the intention?
     
  3. supraman215

    supraman215

    5
    0
    Nov 5, 2018
    Yes. I want it to be able to run in both states, with mains or without mains I don't really care if it's charging at the same time the amp is on I only really want it to be able to be charging when it's plugged in or running the amp when it's plugged in, if it's doing both when it's plugged in that's not a problem but not a requirement either.

    Also I don't care if you unplug the mains and it temporarily powers off when it switches to battery.

    So there's a connection I haven't drawn up there because I didn't know what it would be, and that's the connection between the battery and the amp.
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    8,686
    1,691
    Nov 17, 2011
    Why not simply power the amplifier always from the batteries?
    With mains power available, the charger will charge the battery and the batteries will deliver power to the amp.
    Without mains power the batteries alone will power the amp.

    If you definitely don't want that setup, use a double pole dual throw relay (DPDT) with a 12 V coil.
    upload_2018-11-5_14-38-42.png
    The coil is powered from the 12 V supply.
    • If no power is available, the relay contacts are closed as shown, proding the amplifier with power from the battery pack.
    • If power is available, the coil is energized and the relay contacts are closed opposite to the positin shown, connecting the amplifier to the power source and disconnecting it from the battery pack.
    No fancy electronics is required.
    All you'll notice is a short outage of the amplifier when the relay switches.
     
    JWHassler likes this.
  5. supraman215

    supraman215

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    Nov 5, 2018
    This is perfect exactly what I needed. Thanks so much. Couldn't I leave (-) connected through the whole circuit and just get a single pole dual throw relay? Thanks again this is such an elegant solution, so simple, can't believe I didn't think of it.
     
  6. Bluejets

    Bluejets

    2,976
    577
    Oct 5, 2014
    To cut down on the number of add on modules, there are available 18650 cells with protection circuit already built-in.

    As with any of these bought from China, be cautious of the ones claiming large capacity (4000-5000mah) for a couple of dollars each.

    https://www.ebay.com.au/itm/TrustFi...h=item3af923e788:g:9EIAAOSwpINaIN1X:rk:1:pf:0

    There are also charge modules available that will power the circuit AND charge at the same time.
    Ones I use are for single cells but there may be others for multiple cells in series, you'll just have to do a search for yourself I'm afraid.

    Would not need any changeover or relay BUT it would be charging as well as discharge but i can see no problem there as the module limits the charge current. Just have to provide as an example, a charger for the 1A of the module capacity.

    As example, connection to module below is, power in one end, either usb or solder connection, the other end is battery connections to the centre 2 terminals and the Load to the outer 2 terminals.

    https://www.ebay.com.au/itm/New-2PC...?epid=595263530&hash=item5b399189b3:rk:1:pf:0
     

    Attached Files:

  7. supraman215

    supraman215

    5
    0
    Nov 5, 2018
    Thanks I have plenty of TP4056's unfortunately they do not work in series. Thanks though.
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

    8,686
    1,691
    Nov 17, 2011
    You can if the charger's '-' input and output are directly connected. That is not necessarily the case, however. You'll have to merasure that or look it up in the description of the charger.
     
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