Battery for power outage circuit

Discussion in 'The Projects Forum' started by videoman, Dec 6, 2010.

  1. videoman

    Thread Starter New Member

    Dec 6, 2010
    I live in an area that occasionally has power outages. I am in the process of designing a very simple circuit that will do the following. The house will energize a relay. A lead acid battery will be connected to the common terminals of the DPDT relay. When the power is running, a battery charger will charge the battery through the NO contacts. In the case of a power outage, the relay will fall to the NC position and the battery will be connected to the lights it will power. I plan to use three to six high brightness LED strips made up of 3 LEDs and a single resistor. They are designed to operate on 12vdc and are rated at 25mA per segment.

    My question is this. I am looking for a battery and charger to be used in this design. I need something SAFE that won't gas and or explode as a result of being hooked up to a charger for very long periods of time "theoretically indefinitely."

    I am looking at this battery:

    or possibly this one if you think it would be sufficient in amp hours:

    Now, I saw a deal for a battery charger at Harbor Freight for 5 dollars.

    I would like to know if this would be a safe combination or if I would be better off going with a slightly more expensive option such as this one:

    Thank you for helping!
  2. SgtWookie


    Jul 17, 2007
    Welcome to the Forums. Would you please put your general location in your profile? Click on the "User CP" link above, then on the page that comes up, click "Edit your details", and on the next page, scroll about 2/3 of the way down, and type in your general location. Country and state or province is fine. Then scroll to the bottom, and click "Save changes".

    Meaning 120VAC.

    Have you selected a relay already?
    If not, it will need to be DPDT, and preferably have very low current/power requirements. Remember, you'll be footing the bill for the relay coil to be energized 24/7 for however long it's plugged in.

    How long do you wish for these strips to continue to operate without mains power?

    Batteries don't last forever. If you get 3 years out of them, you're doing OK. If you get 4 years out of them, you're doing very good.

    Since you have not told us the run time desired, it would be difficult to say.

    Coincidentally, the Harbor Freight charger is not suitable for EITHER battery that you have proposed; as it specifically states that it is not compatible with either gel cell batteries (the 1st one) or AGM (the 2nd one).

    1A output would be too much for the 2nd battery, but OK for the 5AH gel cell.
  3. Audioguru

    AAC Fanatic!

    Dec 20, 2007
    The Panasonic batteries are discontinued so they might already be nearing their 3 years life expectancy, or maybe they have been sitting around for years with no charging and are dead and sulphated.