[RE-wrenches] Fw: Xantrex C-40 Drifting

[Ray Walters]

Hi Jarmo;

Early solar systems actually tried to use the principle of matching 
array Vmpp to battery voltage  in lieu of charge controllers.  The 
biggest issue is that when it is is hot the module voltage can drop 
below the battery voltage needed, and when its cold the voltage will 
still be too high.   Batteries were either over charged or never reached 
full charge depending on the conditions.
I've used the C40 successfully for decades, so I'm wondering if the 
circuitry changed recently, or if different tolerance components were 
substituted that may be causing the drift?

Thanks,

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 5/19/2015 10:31 AM, Jarmo.Venalainen at schneider-electric.com wrote:
> Hi:
>
> I didn't know that there were systems out there where a PWM charge 
> controller such as the C-40 was producing an unhealthy, high battery 
> voltage.  Since there are, I may have a possible explanation.
>
> The C-series and other PWM type charge controllers operate by PWM 
> whereby they very very quickly connect/disconnect the solar module to 
> the battery bank.  The amount of time which the module is connected to 
> the array is the PWM on-period.  These controllers do not have the 
> ability to "smooth out" the output voltage.  All they can do is apply 
> the full module voltage OR not a

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