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  • Is there a better way?

    1459182_10202028832256801_1227512199_n.jpg

    This is the battery bank that runs our satellite internet in DR Congo. After some reading I have been doing it seem like too many batteries to have in series then paralleled together. Are we unequally draining our batteries? Is there a better way?

  • #2
    Kind of hard to tell what is going on without a schematic. Nice neat work but other than that is all I got. A general rules is not to ever parallel batteries unless necessary, or it is a Critical Mission where a battery string needs to be taken off-line for maintenance while leaving one string in service.

    As for how many in series the answer is whatever it takes to meet a voltage spec. Here is the deal, it is all about weight and handling. Let's say you need a 12 volt 1000 AH battery. There is no such battery available because it would be too heavy and large to move at around 600 to 700 pounds. About the largest 12 volt battery you can find is about 200 AH weighing in around 125 pounds each which is manageable. So one that is ignorant about batteries would chosse to use 5 of them in parallel which is a really bad idea.

    Better approach is to use 6 2-volt 1000 AH batteries in series. For example a Rolls S-1380 that weighs in around 115 pounds each. Takes up less space, less wire, less maintenance and will last a long time.
    MSEE, PE

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    • #3
      From what I can see in the picture, I would guess that you have 12 strings of two 12V batteries each wired in parallel to produce 24 volts.
      That is a horrible design and will result in some battery strings failing long before the others.
      It is hard to tell whether you even have a diagonal connection setup (+ fed from one end of parallel run and - fed from the opposite end) or not, since the + side is hidden.

      If all these batteries are doing is sitting on float waiting for a power outage, they might stay reasonably well balanced. But if any significant amount of current is drawn from them, the batteries on the end are going to suffer.

      Dereck (Sunking) has given you the outline of the right way to do it, but a lot of the detail will depend on what your load current and charging current profiles are and how long you need to the battery bank to be able to power the load by itself.

      For some real numbers on what happens when you parallel batteries, you can look here.
      Last edited by inetdog; 04-04-2014, 04:38 PM.
      SunnyBoy 3000 US, 18 BP Solar 175B panels.

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