controller selection

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rama
rama Solar Expert Posts: 36 ✭
in Solar Beginners Corner #1
Hi all first post here -
I have a 12V battery system with 24V panel (Voc=43).. and someone recommended a 24V MPPT controller to me. While the voltage input matches with panel voltage, will it safely charge a 12V battery? Will it overload the battery? I would like for this to work without changing my battery from 12V to 24V, if possible. I am aware of the voltage drop effect from panel to battery so my guess is that it's ok.

Here's a brief spec of the controller, can someone pls take a look and confirm? thank you very much.
input
-max pv array v = 50 @ 24V
-max current = 700w
-max current = 21A

output
-nominal battery v = 24V
-max charg current = 30A
-standby power = 2w
-ripple voltage = +/- 1V
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  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    #2
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    Re: controller selection

    If your solar panel is under 200W, use SunSaver 15A MPPT controller. It will convert your 24V panel to correct voltage for 12V battery.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #3
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    Re: controller selection

    What is the actual ratings of the solar panel(s) (Voc, Vmp, Imp, Isc)...

    And what is the AH rating of your battery bank?

    Assuming it is a good quality MPPT controller--it should be able to use ~450-580 watts of solar panels while charging a 12 volt battery bank...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rama
    rama Solar Expert Posts: 36 ✭
    #4
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    Re: controller selection
    AntronX wrote: »
    If your solar panel is under 200W, use SunSaver 15A MPPT controller. It will convert your 24V panel to correct voltage for 12V battery.

    thanks for the recommendation. but actually i'm getting this MPPT 24V controller for a very good deal so i'm just wondering if going ahead would result in any safety or damages to battery (reduce battery life) etc?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #5
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    Re: controller selection

    Assuming the controller is MPPT and has a 12 volt setting for charging your type of battery bank--then you should not have any problems (assuming panels match controller's requirements).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rama
    rama Solar Expert Posts: 36 ✭
    #6
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    Re: controller selection
    BB. wrote: »
    What is the actual ratings of the solar panel(s) (Voc, Vmp, Imp, Isc)...

    And what is the AH rating of your battery bank?

    Assuming it is a good quality MPPT controller--it should be able to use ~450-580 watts of solar panels while charging a 12 volt battery bank...

    -Bill

    Thanks Bill.
    Here's the info - 175w panel Voc=43.14, Isc=5.15, Vmp=33.58, Imp=4.69. Battery Ah rating is 200Ah.

    Unfortunately the problem here is the fact that it doesn't have a 12v setting for battery charging, only 24. So I'm just wondering if it's ok to charge.
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  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    #7
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    Re: controller selection

    It will probably not even power up from 12V battery if it's made for 24V system. What is the name and model of this controller?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
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    Re: controller selection

    Me thinks we might be hearing about the dreaded BZ again!

    Or maybe that Chinese unit that was out there on Ebay a bit ago.

    If you are looking for a "real" controller, consider the Rogue 3024mppt, or the Morninstar 15 mppt.

    Tony

    PS Be advised that some cheese ball controllers (like the BZ) may not perform at all, and some might actually damage a battery bank. I had a BZ on the test bench that actually performed WORSE than having no controller at all, at least in terms of watt/hours of harvest.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #9
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    Re: controller selection

    At best, it will work as an unregulated charge controller--just dumping energy into the battery bank.

    At worst, the controller may see the battery as under voltage and not charge at all (not likely, but possible).

    Not a good solution. I assume that this is a cost issue?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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