Battery Bank Fuse Plan

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Comments

  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Battery Bank Fuse Plan

    Alright.... This oughta settle things. 8)

    Where would you put the shunt for the battery monitor? Hmmm? ;)
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Battery Bank Fuse Plan

    That was not on the stamped and approved shop drawing. So when you send us a P.O. for the up charge for this change order. Then we will tell you where to stick the shunt of yours !!!!:D:D:D:D
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Battery Bank Fuse Plan

    Hey! Look out!

    Admittedly, the shunt was not included in the original shop drawing and, consequently, there is only one place that it can now be "stuck." Middle management has subsequently suggested that such installation be oriented sideways. :blush:

    Heads will roll!
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery Bank Fuse Plan

    Craig;

    The correct answer is: if you are using a battery monitor there is no point in trying to do the dual-diagonal bit, as the monitor will do a much better job of showing any in/out discrepancy than will looking at the figures on the charge controller and comparing them to the ones on the inverter.
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Battery Bank Fuse Plan

    Marc,

    Yep, I get it. Post #32 was humorously offerred as bait. Now that the "double diagonal" issue, which was not part of my OP, has been settled, I will attempt to point this discussion back toward battery bank fusing.

    I now see that the two parallel 75A fuses in series with the 150A is redundant since if the current out of the bank exceeds 150A, any one of the three could blow. Which one goes first will be due to random chance or minute differences in cabling resistance. If the 150A is first to blow, nothing else will. If one of the 75A fuses blows first then the other 75A will immediately follow and then nothing else happens.

    So it would seem that using just the one 150A is the best plan. It is certainly sufficient. However, my desire is to provide some method to prevent or detect certain types of battery failure. My batteries are AGMs and their specific gravities cannot be measured making it difficult to determine their condition. Of course, voltage measurement can be used to check relative battery health but the accuracy of this method is dubious. It also requires a full charge (not a problem) and a hours long rest period before measurement is made. Also, this should probably be done separately on individual batteries that have been removed from the bank (a huge inconvenience.)

    The other option is to use just the two 75A fuses, effectively in parallel, and remove the 150A. I am willing to concede that a shorted cell will not sufficiently imbalance the current draw between the two series strings to blow a 75A fuse, neither would uneven charging/discharging. However, this fuse configuration will easily detect an opened cell failure. How likely is it that such a condition will occur? My guess is "not very." But it is one point of failure that would otherwise go unnoticed until it was too late. Meanwhile, one battery (the one that failed is out of the picture) is neither charged nor discharged, while the remaining two are called upon to supply twice their design current load.

    If responses are lacking, I will probably choose to use the one 150A fuse at the positive terminal of the battery bank. It is a Blue Sea terminal fuse.

    This has been a good thought experiemnt for me.

    Thanks

    K
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery Bank Fuse Plan

    The only advantage I can see to dual fuses instead of a single one is the same as with dual fuses on multiple parallel banks. It wouldn't matter if you put the fuse in-between two batteries in series or "at the end" of them; they're still in the circuit.

    I've kicked this around a bit and don't see any advantage to it. But it was interesting to think about! :D
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