Which SMA Grid tie is the best for future expansion

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South Africa
South Africa Solar Expert Posts: 295 ✭✭✭
in Solar Beginners Corner #1
I have been told that there are SMA grid tie inverters that have more than one MPPT controller built in, that then allows you to start with a string on a controller and then later, when you have more power requirements, with a different set of panels, you can add another string.

Does anyone have experiences with SMA?
Has anyone done the above?
Which model is the best option to do the above with?
5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    #2
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    Re: Which SMA Grid tie is the best for future expansion

    it's been 3 years since I installed sma sunny boy inverters, but back then the only company that sold GT inverters with multple string controllers were the Auroa Power One.
    You can always just oversize the inverter if you want to add another string of panels latter on.
    For example use a 5kw sunny boy and only install about 2.5kw worth of panels, say a string of 14, then latter on install another string of 14.

    this gets trick though , because two years latter the panels you bought could be out of business. you're really got to do your homework.
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  • South Africa
    South Africa Solar Expert Posts: 295 ✭✭✭
    #3
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    Re: Which SMA Grid tie is the best for future expansion

    What I have learned so far: The SB3000 up to 5000TL-21 units have two MPPT’s.
    http://www.sma.de/en/products/solar-inverter-without-transformer/sunny-boy-3000tl-3600tl-4000tl-5000tl-with-reactive-power-control.html#Technical-Data-8621

    Generally the units with one MPPT, under the new transformerless units are marked ST for Single Tracker.
    rollandelliott wrote: »
    You can always just oversize the inverter if you want to add another string of panels latter on.
    For example use a 5kw sunny boy and only install about 2.5kw worth of panels, say a string of 14, then latter on install another string of 14.

    This gets tricky though, because two years latter the panels you bought could be out of business. you're really got to do your homework.

    Been there, done that re panels where supplier stopped manufacturing. :-)

    BUT (I am told), the inverters with 2 controllers, you can start off with one string with max panels for that strings. Later when you want more power, then you can get a different make and model string of panels for the 2nd controller for the 2 strings do not have to match, as they are separate controllers.
    5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    #4
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    Re: Which SMA Grid tie is the best for future expansion

    Dual MPPT tracking gives the solar designer way more flexibility. The new SMA-TL and the Power-One (now ABB) Aurora's are the only GT inverters that have this so far (not counting u-inverters). SMA's were only 3 to 5kW but just started shipping 6kW units (Yay). It used to be that as panels became more and more powerful, big gaps in the possible array sizes formed as had to be even number of panels and satisfy the restrictive Vmin and Voc range. Now, with dual MPPT, you can do any size array with odd numbers of panels, different size strings, multiple roof angles, and even add more later as you want to do. Now we just need inverters with built-in 4 hours of magic battery storage and grid stabilization!
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