Understanding charge controller spec

New_ClimberNew_Climber Registered Users Posts: 12
I just want to ensure I am understanding what I read on for the charge controller spec.

When looking at charge controller like the Morningstar SunSaver 15 Amp MPPT Solar Charge Controller, is the 15amp rating what is coming from the panels into the batteries.

Where my confusion comes from is this has nothing to do with using an inverter correct? The charge controller specs are what the PV panels are putting into the batteries...is this correct?

I currently have 2 panels, 33v (45voc) totaling 380watts peak power....I want to setup something up to run my lights in a detached garage. at 380w setting up a 24battery system, so that would be 380w/24v=15.8amps.

It is this amps coming from the panels into the batteries that the controller needs to handle.

Is my understanding correct?

At first I was thinking the charge controller needed to handle the output of the batteries to the inverter to run my lights...but that is a completely separate device....right??

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Understanding charge controller spec

    Correct. The Amp rating on a charge controller is the maximum current it can pass from the panels to the batteries. It has nothing to do with how much an inverter draws from the batteries.
  • firerescue712firerescue712 Solar Expert Posts: 95 ✭✭
    Re: Understanding charge controller spec

    The output (to the batteries) is 15 amps max. In order to achieve this, the total input wattage should be 200 watts for a 12 volt battery and 400 watts for a 24 volt battery. If you have 15 amps coming into the charge controller, its output will still only be 15 amps max. The charge controller is rated at 75 volts input MAXIMUM! Your panels need to be wired parallel. In series, they would be over the 75 volt maximum.

    The charge controller charges the batteries off the pv system. The inverter is powered from the battery bank.
  • New_ClimberNew_Climber Registered Users Posts: 12
    Re: Understanding charge controller spec

    Thank you much for the explaination...

    Another question...

    Does it matter if I over size my charge controller for my current PV capacity? Right now 15amp capacity would work, but if I purchase the 45amp controller, it would give me future room for more panels. Does the controller work less efficient if it is over sized? Just thinking about future expansion.

    Or, is it better to have separate devices and wire accordingly?
  • SolaRevolutionSolaRevolution Solar Expert Posts: 407 ✭✭✭✭✭✭
    Re: Understanding charge controller spec

    You have it right about the 15 amp output rating to the batteries.

    I think I see some possible confusion though. The Morningstar SunSaver 15 Amp MPPT Solar Charge Controller also has a "lighting control" or a "Load Control" circuit. This is also rated at 15 amps DC. It is intended to turn DC lights (or other DC loads) on and off based on preset conditions.

    See manual section 3.2. Factory presets:
    Switch 2 OFF (↓): LVD = 11.50 V, LVR = 12.60 V
    Switch 2 ON (↑): LVD = 11.00 V, LVR = 12.10 V

    Also from the manual:
    Using MSViewTM PC software, the SS-MPPT can be
    programmed with custom settings to function as a lighting
    controller to turn the system loads on and off at specified
    intervals throughout the day and night. See section 4.7 for
    more information.


    If you want to use this to control an AC load (or a DC load which exceeds 15 amps) you may be able to use it to drive the DC coil of a relay. (The relay coil voltage must match the battery voltage and the contacts must match the Load voltage and current requirements.)

    -Alex Aragon
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Understanding charge controller spec
    Thank you much for the explaination...

    Another question...

    Does it matter if I over size my charge controller for my current PV capacity? Right now 15amp capacity would work, but if I purchase the 45amp controller, it would give me future room for more panels. Does the controller work less efficient if it is over sized? Just thinking about future expansion.

    Or, is it better to have separate devices and wire accordingly?

    There isn't much problem running an oversize controller, especially if you're planning on future expansion. It would be silly to buy an 80 Amp controller for 20 Amps of course. But on the other hand it is actually desirable to have some "overhead" instead of running at peak current all the time.

    If you know you're planning on a 3X increase sometime soon, go for the 45 Amp controller. Technically there is some inefficiency in running one so lightly, but it's not a big enough value to worry about.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Understanding charge controller spec

    some also opt to use multiple mppt controllers and add them as the expansion dictates. if you got 2 more of those pvs down the road and already have 2 pvs with a sunsaver 15a mppt cc then you could just wire the 2 new pvs to a new sunsaver 15a mppt cc and then to the batteries. it is basically paralleling a separate solar system to your batteries. separate controllers can be more expensive than a single controller so you should evaluate which way you'd want to go with it. most do opt for the larger single controller.
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