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Lead acetate batteries rechargeable?

Discussion in 'Electronic Basics' started by W. eWatson, Aug 21, 2012.

  1. W. eWatson

    W. eWatson Guest

    Are such 12v batteries rechargeable? What type of small (alarm,
    motorcycle) batteries are rechargeable? What do I need to recharge them
    with? Is a gel battery preferable? What is gel?

    I need it for a Celestron telescope, 6" mirror. I had a lead acetate
    for the scope, and it seemed like it could be charged with a jumper
    battery I have. In any case, it seems unusable now--after two years of
    occasional use. Maybe 12 uses for 2-3 hours each in that period.

    Maybe this is the ticket.
    <http://www.amazon.com/Rechargeable-Sealed-Lead-Battery-Electronics/dp/B000BPCUXO>.
    It's lead acetate, so that answers one question. Maybe the one about a
    recharger too. Does a recharger service have to match up with the battery?
     
  2. Phil Allison

    Phil Allison Guest

    "W. eWatson"
    ** Yes.

    And the name is " Sealed Lead Acid" or SLA

    What type of small (alarm,
    ** Ever hear of Google ??

    ** It helps.....

    .... Phil
     
  3. W. eWatson

    W. eWatson Guest

     
  4. W. eWatson

    W. eWatson Guest

    How is the % measured? With what instrument?
     
  5. ehsjr

    ehsjr Guest

    A 12V lead acid battery is considered 100% discharged when
    the voltage at its terminals measures 10.5 volts. Discharging
    it that far causes damage. I don't know what the poster has in
    mind by his 50% figure, but if you figure it as 12V-10.5V * 50%
    it's 11.25V, which is a sensible cut off voltage. The cut off
    voltage is the level you set at which the circuit will disconnect
    the battery from the load so that no further discharge occurs.

    Ed
     
  6. W. eWatson

    W. eWatson Guest

    ....

    battery). I charged the batteries quarterly even if they were not
    A poster slightly above my post mentioned %. Not me. Anyway thanks for
    the clarification.
     
  7. W. eWatson

    W. eWatson Guest

    I have a 12v Xantrex 600HD that has a meter on it. Maybe there are
    rechargers for less hefty batteries that have a meter?
     
  8. ehsjr

    ehsjr Guest

    A recharger with a built in meter doesn't fit in with what was being
    discussed, which was the level to which a battery was _discharged_.
    If you have to monitor a recharger with a meter, throw it away
    and get one that _automatically_ provides a proper charge to the
    battery, regardless of whether you're watching a meter or not.

    With regard to the discharge cycle, you want an _automatic_ circuit
    to protect the battery - a meter provides only monitoring and measuring,
    not automatic disconnect. If all you have is a built
    in meter and you're not paying attention to it, you can easily
    discharge the battery too far.

    A cheap VOM will likely be at least as accurate as a meter built
    into a power pack.

    With regard to your Xantrex: the owner's manual states that the
    charge % indicator is accurate only when the unit has been
    disconnected from all loads and charging sources for at least
    15 minutes. The manual also states that the unit will sound
    an alarm when the voltage drops to 11 volts, and automatically
    disconnect from the load when the voltage drops to 10.5, provided
    the AC outlet on/off switch is turned on. That's the right idea,
    but the wrong implementation. The voltage levels should be
    higher - 11.5 volts for the alarm, and 11.0 volts for the
    disconnect. In addition, the alarm and disconnect functions
    should not depend on the position of the AC outlet switch, they
    should operate any time current is being drawn from the battery.
    It is obvious that the Xantrex was not engineered for maximum
    battery life, nor the more or less permanent usage in your
    dome/telescope. That doesn't mean you can't use it for that - you
    can. But the questions you have asked over a long period of
    time have been more detailed in nature than something like:
    "What is the easiest way for me to power the dome?"
    If you want the easiest way, just use the Xantrex or equivalent
    to bring power out there each time. It still means you need to
    do some research to find out if your controller(s) and motors
    will work properly for long enough on the 12V DC that the
    Xantrex/equivalent can provide, and how often you need to
    recharge.

    Ed
     
  9. W. eWatson

    W. eWatson Guest

    Per Google, I see they are probably called float (or automatic) float.
    Some are pretty pricey. I think I'll pass in favor of using my VOM, as
    necessary. For the 6" scope, I do not think this poses a problem. More
    below.
    My (second) Xantrex turned out to be a stinker in that despite charging
    it every 3 months, it is barely in the game anymore.

    Ah, you remembered my dome/obs. There is where I would need a (float)
    automatic recharger. It will easily run the 6" scope, but it sure is bulky.

    I've run into a blank wall with regard to providing control of the dome
    shutter and rotation to keep the shutter open where the large scope is
    pointing. First though, I bought a hefty 12v Kirkland deep cycle battery
    from CostCo back around Feb or March. It has not been used, but I do not
    think has significantly discharged. The charger (float) need I mentioned
    in the last paragraph would probably be helpful there until and when I
    get the battery in use.

    Regarding the dome control project, I think there may be one guy in the
    50 states who knows how to do this, and he lives in Hawaii. He does it
    for a living. In the last 6 months, I've managed to purchase the
    Kirkland battery, soft start device, power inverter, aluminum sheets for
    shelves on the dome walls, relays, NEMA box, and a few other parts. In
    that time, I've had five people here who could likely do the job.
    Eventually, all but one showed up to do it. I've offered attractive
    money. The one who did show up got a real job and disappeared. My last
    resort now seems to be the fellow who built the obs. He tells me his son
    may have the skills to install the circuit cards, and wire up matters.
    I'll know in early Sept. If I knew more about relays, I could probably
    do it myself. If you or anyone lives near Sacramento, CA I have a job
    for you. :)
     
  10. ehsjr

    ehsjr Guest

    Wish I could, because it is an interesting project, but I'm in NY.

    Regarding the charger: if all you want is a float charger,you can build
    that cheaply and easily. Note that a float charger will not
    charge your battery properly, where properly means a 3 stage
    charge cycle. But it will work to keep a battery at full charge,
    and will charge a partly discharged battery to full charge,
    given enough time. If your battery usage is such that a float
    charger has enough time to recharge the battery between uses,
    then you can get away with that, and it doesn't need to
    be automatic. The float charger provides a fixed voltage at
    a low current, and won't overcharge your battery when it is
    properly designed. It's not as good as a 3 stage charger, but
    it may be perfect for your needs, and it costs way less.

    To build a float charger, get Item Number 18724 PS from MPJA
    and Catalog #: 276-1141 from Radio Shack. Wire the two
    diodes contained in the package from Radio Shack in series
    with the + lead from the 15 volt regulated supply from MPJA.
    Like this:

    ------ D1 D2
    | +|--->|--->|----to batt +
    | PS |
    | 15V |--------------to batt -
    ------

    Note that the banded end of the diodes must be as shown.

    That will provide ~13.8 volts to the battery. It is not
    a *perfect* float charger, but is darn close. It's just
    3 parts and is really simple to put together.

    The diodes cost $1.59 for 2, the MPJA supply is $5.95. See:
    http://www.mpja.com/15VDC-16A-Regulated-Plug-Supply-GME/productinfo/18724+PS/

    (watch out for line wrap above)

    By the way leaving your Kirkland battery alone - that is,
    not giving it a charge every so often - will eventually kill
    it. Give it a proper charge once a month or so, or put it on
    float charge.

    Ed
     
  11. W. eWatson

    W. eWatson Guest

    ....
    Thanks for the tips. I bought a Schumacher 1.6 A Speed Charter
    Maintainer for the Costco battery.
     
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