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SLA's in Cars

Discussion in 'Electronic Design' started by RoD, Apr 28, 2004.

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  1. RoD

    RoD Guest

    Hi All.

    I want to add a 12V SLA to my car, so that I can power my CD/Tuner deck (a
    Sony Xplod 200W) when the engine is not running, without the chance of
    flattening my main battery.

    Also, when I start my car, all of the accessories are disconnected from the
    battery while the started motor is on, and this disconnects my deck for only
    about 1sec, but it then takes ten/fifteen seconds to get back to playing the

    So, my idea is this.

    I have the SLA permernantly connected to the deck, via a switch that allows
    me to switch the deck on/off with any key in the ignition. And also to have
    the SLA battery connected to the cars electrical system via a relay, so that
    it charges when the ignition is in the "on" position only.

    But is it OK to leave a 12V SLA connected to 14.4V for extended periods of
    time? I know that this is enough to charge it, but is there a danger of
    overcharging the battery and damaging it. If so, do i need to add a
    charging circuit, or maybe just regulate the voltage (to around 13.5V).

    Any feedback would be appreciated
  2. j.b. miller

    j.b. miller Guest

    You shouldn't have any real problems, my friend uses two older Gates SLAs to
    run his old(74) Mini. He's never had a problem...
  3. RoD

    RoD Guest

    OK, thanks.

    Well, i read something that said applying more than 2.25V per cell
    (i.e. 13.5V for a 12V battery) would overcharge the battery, and would
    slowly reduce the batteries capacity, and could also cause the safety
    valve to vent gas.

    Since the open circuit voltage of a fully charged 12V SLA is 12.9V
    (2.15V per cell) 13.5V should be sufficient to charge it, and maintain
    it at full charge without damaging it.

    Does this sound about right?

    Thanks all.
  4. j.b. miller

    j.b. miller Guest

    Depends on who makes them. Gates Cyclone batteries, at least 18 years ago,
    where 2.35 per cell.
    Best to get the right numbers from the manufacturer.
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