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Sealed Lead Acid Battery - Do I need to current limit for a low current application?

Discussion in 'Electronic Basics' started by bonzo, Apr 20, 2004.

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  1. bonzo

    bonzo Guest

    Hello there,

    Somebody once said there are no dumb questions... so here's mine!

    I have a device that I would like to run for an extended period of
    time, say 2-4 days. The device requires 12V and 80mA and provides a
    constant load i.e. there is no power surging.

    I recently acquired a Power Patrol SLA1146 battery (12V, 26AH). Can I
    contact this battery to the device without any power buffering
    circuitry? I'm concerned about blowing the device. Will the device
    only draw the 80mA is needs?

    Yes, I missed that day in Physics class!

  2. CFoley1064

    CFoley1064 Guest

    Subject: Sealed Lead Acid Battery - Do I need to current limit for a low
    You'd have to describe your load circuit to get a better evaluation. If it
    says 80 mA, there might be a capacitor input that requires a momentary surge in
    current. Lead-acid batteries are OK with this -- it's the non-momentary short
    that you have to worry about. That causes heating in the battery, with
    potentially bad results.

    When you're looking at protecting battery power supplies, you have to look at
    what *could* go wrong. Worst case, if your load shorts out, you could have
    some serious problems. If you feel it's worth it, a 1/4A 3AG fuse with in-line
    fuseholder is cheap protection, and will add practically no voltage burden.
    They're available at Radio Shack, hobbyist sources, hardware and auto parts

    Good luck
  3. bonzo

    bonzo Guest

    Thanks Chris! Your comments make sense. You're right about the no load
    situation, that's what I'm worried about - the last thing I want is a
    fire in an enclosed space. The "device" is one of those cheapo cameras
    and I'd like to use it to monitor my driveway and garage. Unless the
    RF circuitry needs some kind of charge pump, I don't think there are
    any caps(?). Is the fuse you suggested put on the "+"ve side of the
    SLA battery?

  4. Rich Grise

    Rich Grise Guest

    Strictly speaking, as long as it's anywhere in the circuit, it will
    interrupt the current. But in the positive lead is probably the most

    And, I dunno about that 80 mA load on a 26 AH battery ... lessee ...
    26 / .08 equals, um - almost two weeks?

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