Rechargeable backup batteries?

Discussion in 'The Projects Forum' started by jatchan, Apr 14, 2008.

  1. jatchan

    Thread Starter New Member

    Apr 4, 2008
    Is there any ways that I can use rechargeable batteries to power my 12V microcontroller if the AC power cuts out?
    The microcontroller requires 12V 500mA to operate. I wanna use rechargeable batteries for around 10 hours backup so it will still do its work even if the AC power is not providing. What kind of rechargeable batteries do you recommand and how do I connect the circuit? Thanks!
    Note: I'm currently using a 12V 1000mA DC adaptor for microcontroller.
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    You'll need batteries rated for 5 Amp-Hours. These are commonly available. A plethora of lead-acid batteries fit the bill.

    I hope "light weight" was not one of your requirements.
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    I think there is a glut of 12 volt 7 AH batteries available in the $20 range. Always good to have excess capacity.
  4. SgtWookie


    Jul 17, 2007
    You'll still need a way to charge the battery, and to regulate the voltage to the microcontroller.

    A 12v 1a supply isn't high enough voltage to charge the battery.

    As the battery discharges, the output voltage will drop. Lead-acid batteries are considered fully discharged when each cell reaches 1.75v, or 10.5v for a 12.7v battery. But, running them down to a full discharge shortens their life quite a bit. Better to not discharge them more than 30 percent for maximum life.

    What's the tolerance on the microcontroller's 12v requirement?

    You may need to use a dc-dc buck/boost converter on the battery output.