Dual Xantrex C40 Charge controllers: auto Equalize?

2twisty
2twisty Solar Expert Posts: 199 ✭✭✭
in Off Grid Solar & Battery Systems #1
Got a system with 2 Xantrex C40s. Should I set both to auto equalize or just one or neither, and do it all manually?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    What is the array current per controller?

    What is the Battery Bank AH capacity?

    Assuming the Battery Bank is fully charged, to equalize you would need around 2.5 to 5% of the battery bank AH rating as "equalization" current If one C40 can supply that amount of current, then only one would be needed.

    And, what is your present S,G. measurements for the cells--Do you have a spread of 0.015 to 0.030 between low and high SG readings in the battery bank (or greater)?

    Do you plan on equalizing when the SG range >0.0xx units, or do you plan on equalizing once per month? (different mfg. recommend different things)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • 2twisty
    2twisty Solar Expert Posts: 199 ✭✭✭
    #3
    This is a system that I am assembling for a friend. I doubt that she will monitor SG closely enough to determine when an EQ is needed, so I plan to set the EQ monthly. The Xantrex can be set to auto-EQ monthly, and one of them can easily supply that much current in the existing configuration. So, for now, I guess I'll set one to do an EQ monthly and the other set to manual

    If I were in the situation that I needed the current from both charge controllers, there seems to be no way to coordinate the two controllers to EQ at the same time. If that were the case, would I have to switch to manual EQ? Right now, she has 8 T-125s, but plans to purchase 8 L-16s in the next couple months and sell the T125s to a neighbor that will be building a much smaller system. Once we have 8 of the L16s at 430Ah, I will definitely need both controllers to EQ a bank of that size.

    So, is Manual EQ in her future? Maybe I can convince her to buy a Classic 150 and sell these Xantrex controllers to the neighbor.... I'd much rather see her using MPPT, anyway.

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    I agree with your assessments. Limitations of hardware and $$$.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #5
    If the array will not produce 10% of the battery capacity, I would suggest she is planning on having too small an array for her battery bank. She might consider smaller capacity L16's or slightly smaller batteries in 350 - 390 amp hour range. Of course it might be a cabin that gets little use, but for a daily used home, I'd shoot to have close to 10%.

    I've got no problem with C40s of pwm charge controllers with solar panels in the correct voltage range. I used a couple pwm cc for several years both of which are over 15 years old and still functional.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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