[RE-wrenches] Re-configuring expanded array

Fri Sep 30 08:11:12 PDT 2011

Hi Holt,

Ditto what Allan said....Or, If you must have the extra power, add a separate charge controller to operate those two PV modules. 

I assume that the modules are already owned since you would not design a system with mixed modules. Mixing different PV modules will always cause a loss of potential power when using MPPT controllers. However, you don't have much choice from an economic standpoint. Just try to match the Vmp between the strings.

Larry Crutcher
Starlight Solar Power Systems

On Sep 30, 2011, at 7:23 AM, Allan Sindelar wrote:

> Holt,
> The string of two will contribute nothing to the charging, as the combined input voltage will be above Voc for the string of two. Better off storing the last two for spares.
> Allan
> 
> Allan Sindelar
> Allan at positiveenergysolar.com
> NABCEP Certified Photovoltaic Installer
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Positive Energy, Inc.
> 3201 Calle Marie
> Santa Fe, New Mexico 87507
> 505 424-1112
> www.positiveenergysolar.com
> 
> 
> 
> 
> On 9/30/2011 7:55 AM, holtek at sbcglobal.net wrote:
>> 
>> Battery based grid tie system
>>  
>> Current array: 20 modules - 5 strings of 4
>> Proposed array: 32 modules - 10 strings of 3, 1 string of 2 - all to MNPV12 combiner
>>  
>> changing charge controller (long story) and expanding system to 2 CC's. voltage limits me to 3 max in string.
>>  
>> Question: is the 3-2 mix of strings an issue? Also - would modules of slightly different voltages in the same string be an issue?
>>  
>> Think I know the answer - that's why I'm asking others.....just want to be sure
>>  
>> Holt E. Kelly
>> Holtek Fireplace & Solar Products
>> 500 Jewell Dr.
>> Waco TX. 76712
>> 254-751-9111
>> www.holteksolar.com

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