Heterogenous 48v Battery Bank

System
System Posts: 2,511 admin
in General Solar Power Topics #1
Hello

I know that each 2VC cell of the 24 batteries in a heavy-duty 48VC battery bank must be of the same type and size.

http://www.hoppecke.com/produkte/anwendungen__1/it_telekommunikation/opzs

But, for example in a 1000AH bank is it possible, in the middle of them to have 6 cells of 1200AH (Thus in serie ==>9 batteries 1000ah + 6 batteries 1200ah + 9 batteries 1000ah).

What incidences would have them concerning the charging capacity of the bank, the life time of it, the equalizing of these cells and of the 18 other ones, the MPPT charging process of a MX60 regulator ....

thanks for your replies
jacques

· Share on Twitter

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Heterogenous 48v Battery Bank

    you would not be able to utilize the extra capacity those cells would introduce as it would be limited by the weakest cell capacity. it would essentially be a 1000ah string. there may be some issues with it during the eqing of the batteries, but i'm not the expert on that scenario.
    · Share on Twitter
  • System2
    System2 Posts: 6,290 admin
    #3
    Re: Heterogenous 48v Battery Bank

    Hi NIEL

    I thought in such a string, this extra capacity in the middle of it, could easier improve a coutinuous floating and equilazing. But my fears are about the life of the bank.

    jacques
    · Share on Twitter
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Heterogenous 48v Battery Bank

    doing that will not extent the life of the bank. as with any battery the proper charging, discharging, and maintenance will do the best for them. if the battery is better made to begin with that helps even more with lifespan, but that increases the initial costs too. even a good expensive battery not charged, discharged, or maintained correctly could die quicker than those of the cheapo batteries that are taken care of right.
    · Share on Twitter
  • System2
    System2 Posts: 6,290 admin
    #5
    Re: Heterogenous 48v Battery Bank

    If the batteries are in series, that means the SAME current will flow through EACH battery, regardless of where it is located in the string. Period.
    This means, that to fully charge the bigger capacity cells, again regardless of where they are in the string, the smaller cells stand to be overcharged. However, to just bring up the smaller cells to full charge, will leave the bigger ones undercharged. Yes, normally you only have to replace what has been taken out, so to speak, but all batteries self discharge and the larger ones will do so at a greater AH rate, so as time goes by, they will drift down, while the smaller ones could well drift into overcharge. To equalize the larger cells in the string, will really boil the smaller ones. Again, REGARDLESS of where they are in the string.
    Cheers
    Wayne
    · Share on Twitter
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Heterogenous 48v Battery Bank

    yes that would be an eq issue and i did make light mention of that. bottom line is it's a bad idea to do that. when you have batteries they should be identical to avoid problems that go beyond the norm. wayne is 100% right and that would lead to being undercharged for the larger ones and destroy them through sulphation and the others would boil out there electrolyte through overcharging also leading to sulphation.
    even identical batteries, but of different ages aren't good to use. anything that sets up a difference even if minute is not recommended.
    · Share on Twitter
  • System2
    System2 Posts: 6,290 admin
    #7
    Re: Heterogenous 48v Battery Bank

    thks U both, I always appreciate a lot your comments.

    jacques
    · Share on Twitter

Categories