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

Jerry Shafer jerrysgarage01 at gmail.com
Fri Jun 24 19:35:32 PDT 2016


Wrenches
One thing to consider is that a good charge controller will cost more then
a few modules so in most cases now with the current pricing is to remove
and replace with new, I would like to keep the old ones in play with what
ever is controlling them but build the new array, stack them up with a FM
80 and forget about it. if you customer is looking long term, I bet that
they would understand and go for it.
Jerry

On Thu, Jun 23, 2016 at 3:04 AM, Jesse Dahl <dahlsolar at gmail.com> wrote:

> 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
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