[RE-wrenches] Building strings of modules with variable voltages?

[Dan Fink]

Dan; rough-and-tumble world indeed here off the grid! My understanding is
that Voc will still be additive, minus degradation over the years, but that
the larger Pmax modules will be current limited for Imp by the smaller
ones. So your 245w modules could only do 100w in the scenario you give.

My solution has always been just stick with PWM controllers in these
situations.
On Jun 22, 2016 10:37 AM, "Daniel Tittmann" <daniel at greenwired.com> wrote:

> In the rough and tumble world of off grid system management for people who
> have been piecing together systems for years it is not uncommon for our
> company to come to a project and find many different types of solar
> modules.  In most cases these modules are working fine and producing power
> but often have different output profiles.   In an effort to upgrade systems
> and increase production I have often had the idea of building string of
> these different modules and feeding them into an MPPT controller.
>
> Can anyone out there explain if this would be a good idea or a bad one?
>
> Let say we have
> 4 x 100 watt 17.5 Vmp modules
> 2 x 245 watt 30.5 Vmp modules
>
> what would be the outcome of 2 strings of modules
> both with: 2 x 100 watt + 1 x 245 watt
> would this cause issues with the MPPT controller (say OB FM60) or the
> modules? Obviously you need to build strings that will fit the profile of
> the controller and not over to the series string rating and voltage
> tolerance of the modules but from a production standpoint where does this
> land?
>
> thanks for your advice
> Cheers-
> Daniel
>
>
>
> Daniel Tittmann
> CTO
> Greenwired
> www.greenwired.com
> daniel at greenwired.com
> 707-923-2001 (office)
> 707-206-5088 (Cell)
>
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