Building my first agm battery bank

Discussion in 'Off Grid Living' started by Jth3rd, Dec 27, 2016.

  1. Jth3rd

    Jth3rd Monkey

    Like title says at work were removing failed ups systems out of turbines and I've been pulling the battery's out saving the good ones, so far I've acquired 140 csb 12v 7.2 ah and about double this amount once we install the new ups designs in the rest of are systems, looking at have 4 battery Banks 105 battery's per bank wired parallel on the bus structure, have a line on solar panel for the setup, looking at making it on a small trailer unit that will have the solarpanels fold out on location with about 3000 ah on battery power
    What's everyone thoughts

    Cabin Lady likes this.
  2. Texas Monkey

    Texas Monkey Monkey

    Be sure to use some type of poss and neg. bus bars,
    once you get more than a few batteries hooked up in a line the end batteries end up being overused during the charging and discharging,
    Give each battery its own number for record keeping,
    I'm sure some of those batteries are in better shape than the others, might help if you could charge each one and then let it sit for a few hours and then test how it holds a charge,
    techsar likes this.
  3. ghrit

    ghrit Bad company Administrator Founding Member

    Those look very much like the batteries that come in APC units. It is recommended to replace them every two years in UPS service, but they will last a LOT longer than that in less critical services. They should all be charged and load tested, but they are good batteries.

    What is the reason for the trailer load of lead?
    techsar likes this.
  4. techsar

    techsar Monkey+++

    Sounds good in theory, but I hate to say that in practice the chances of you getting 140 (or 280) matched used batteries is slim to nil.
    Cruisin Sloth likes this.
  5. ghrit

    ghrit Bad company Administrator Founding Member

    Yep, they need to be tested and matched.
    Cruisin Sloth likes this.
  6. Tempstar

    Tempstar Old and crochety Site Supporter+

    Used to go through a lot of these at work, and here is what I found when I too used to save them: They are near the end of their service life. Being on a constant charge will have sulfated them. A lot will charge to 13.2 volts but in use you will find the capacity has been greatly reduced. No to be a downer here, but those little guys just are not made for the long haul and I hate to see you spend bucks messing with them. Our rate of "still good" ones was about 1 in 25 or so. And believe me, I am one of the original scroungers and wanted so bad for these to be worth the time, but now just watch them go to the recycle.
    Cruisin Sloth likes this.
  7. Tevin

    Tevin Monkey+++

    I'm voting with @techsar and @Tempstar . Mixing good batteries with weak ones pulls all the good ones down. Also, stringing several small batteries together to make one big one looks good in theory, but you get diminishing returns the more batteries you add. You can only take the idea so far. The internal resistance of 140 combined batteries must be...oh my!

    You got them for free so you have little to lose. By all means experiment and see what you can do with them, but don't expect too much.
  8. Jth3rd

    Jth3rd Monkey

    Yeah was looking around running them not in parallel but all connected to a single bus structure, looks crazy may not even work but this is what I was thinking for a bus plate design with about 1/8 inch of insulation between positive and negative bus plates single draw from the middle so no one battery is being used through another battery any inputs on this looking at total cost under 500 most being diy fab work

    battery bank.
  9. arleigh

    arleigh Goophy monkey

    my system has a 3 position switch per component .
    this allows me to test each individual component in line at random with out unnecessary handling, battery, solar panel, wind mill, generator, grid powered battery charger.
    If you don't know what each battery is doing ,one can draw the whole system down.
    1. switched center is isolated off.
    2. switched up is test which I have several panel meters available wired on that circuit amperage and voltage.
    3. switched down is in service connected to the whole system.
    Allow yours self more panel space than you currently expect, chances are you'll need it.
    Don't forget fusing it serious . no mater how careful you are, one moments tired mistake is unmercifully unforgiving.
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