[RE-wrenches] Sunpower modules

[Larry Crutcher, Starlight Solar]

Drake,

I have seen this often. The operating voltage drops as panels age.  
MPPT depends on a higher input voltage compared to the battery  
voltage. When you account for module temperature and age, the panel  
may not produce enough differential voltage for the controller to  
convert into power. If no boost takes place, the controller will act  
like a conventual PWM controller. Good news is that if the controller  
will handle the Voc, you can put the old modules in series and do a  
little better job of reaching the acceptance voltage.

Yes I have sold hundreds of Blue Sky products. The IPN Pro battery  
monitor is the best I have ever installed. Highly recommended.

Larry Crutcher

On Mar 20, 2009, at 9:25 AM, Drake Chamberlin wrote:

> At 09:46 AM 3/20/2009, you wrote:
>> The CTI-90, rated at 5.15 amps, will reach 7 amps here in Yuma with  
>> the Blue Sky 3024i.
>
> Do you use the Blue Sky metering, or have you checked the MPPT  
> output with independent metering?  I retrofitted a 12 V Blue Sky  
> charger on an old cabin system. The CC had no on-board metering.  My  
> measured result showed almost the same output and input on a cool,  
> sunny day.  The modules were ancient Arco units, but I still  
> expected some improvement.
>
> Drake Chamberlin
> Athens Electric
> OH License 44810
> CO License 3773
> 740-448-7328
> 740-856-9648
>
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