Calculation of Vocmax

There are many PV modules available on the market. One of their parameters is probably more important than the others - open circuit voltage. When module is not loaded by electricity, its output voltage is higher than if loaded. Each equipment is designed for certain maximum input voltage and higher voltage may activate its overvoltage protection or damage it. So called "open circuit voltage" of PV modules is besides power tolerance influenced by temperature coefficient that describes how voltage of modules increases with decreased temperature. It moves usually around 1/3% for a temperature degree and so decrease of temperature by three degrees generates 1% higher voltage. Modules are measured in their production at +25°C and so at severe frosts (-20°C) can have even 15% higher output voltage! Hard frosts are usually observed at clear sky and so this property shouldn't be disregarded.

Fill in the table using data from the technical datasheet of modules intended for your installation to determine if those modules meet the requirements.

*Reloading this page will delete entered data and retrieve the template again.

 

Number of modules - number of the same modules connected into the series.
Voc (Open Circuit Voltage) - according to the datasheet (measured at +25°C)
Temperature Coefficient Voc - given in %/°C or %/K, optionally also in mV/°C or mV/K (see the datasheet of PV module). Fill into the correct column, will be shown below in the respective column).
Power Tolerance - usually positive or given as range +/-. Enter only positive value. 
Lowest calculated temperature - (enter lowest temperature reached in the place of  installation)

Vocmax - open circuit voltage of serial combination of modules including all influenced factors. This voltage must be lower than upper limits given for Solar Kerberos units.

OK - calculated value of Vocmax complies with limits of input voltage of Solar Kerberos
Not OK - calculated value of Vocmax is either higher than maximum approved value of input voltage for given type of Solar Kerberos, or is too low for the system to work effectively.