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what amperage

Discussion in 'General Electronics Discussion' started by Defib, Nov 15, 2010.

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  1. Defib

    Defib

    3
    0
    Nov 15, 2010
    Hello

    I am designing a basic portable power pack and I am planning on using a 12v SLA with 7Ah rating.

    Basically it will, when required, need to have a cigarette charger for a cell phone plugged into it and other basic items.

    What draw will the cigarette lighter charger for my phone have??

    Is my selection of SLA correct??

    Will it drive a 12v to 240v Waeco 150w invertor??

    Please assist, I'm not tooo clued
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,271
    2,718
    Jan 21, 2010
    The current it draws will depend on the phone. You can measure this easily if you have a multimeter. The 7Ah SLA seems entirely adequate for this.

    It would drive that inverter at full power for approximately 20 minutes.
     
  3. Defib

    Defib

    3
    0
    Nov 15, 2010
    Thanks for your reply

    So if I use the SLA with say an inline fuse and the car cigarette charger it would be ok???
     
  4. barathbushan

    barathbushan

    223
    0
    Sep 26, 2009
    There is no doubt , that a phone can be charged with your sla battery , since it consumes around 5 to 8 watts , depending on your style of charger , if you use a switched mode charger , you will get higher efficiency than a linear charger

    but i wouldn't connect a 150 watt load , at 12 volts full power , the current drawn is about 12 to 13 amps , which is too high a discharge rate for a 7ah battey .which results in sulfation and shortens the battery life .
    Like steve said the battery will last 20 minutes , but steve should have known that sla
    batteries are not designed to discharge to less than 20 % of the capacity , as sla batteries are not regular "Cyclic" batteries .

    but you can overcome this problem by connecting two same 7ah batteries in parallel , thereby increasing the capacity of the battery to 14 AH at 14 volts , then you can use your inverter to about 45 minutes
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,271
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    Jan 21, 2010
    I'm not sure that I agree with your assumptions about what I should and shouldn't know.
     
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