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

[Jesse Dahl]

Attached are two photos. One shows the IV curve of two dissimilar modules
in series and the other shoes them in parallel.

On Wed, Jun 22, 2016 at 12:37 PM, 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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-- 
Jesse Dahl

RE-Power LLC
NABCEP - PV Installation Professional
NABCEP -  PV Technical Sales
MREA - PV Site Assessor
Solar PV Instructor - Hibbing Community College
IBEW Local 292
218-235-0167
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