[Elecraft] Using the KX1 on Solar Power

[G3VVT at aol.com]

In a message dated 22/06/05 15:26:09 GMT Daylight Time, DolfinDon at msn.com  
writes:

You can  test the output current by connecting a 10 ohm 5 watt resistor 
across the  panel and measuring the output voltage


Reply: .....................................................
 
In practice you do not even need to do that.
 
During some commissioning of a large solar powered microwave system I was  
involved with about 5 years back that used up to 15kW of solar power  at each 
site (200 x 75W 12V solar panels), the contractors who installed the  system 
tested the output by connecting an ammeter effectively directly across  the solar 
panel output terminals. When I raised the question would this not  cause 
damage? They came back quite rightly, no, the current will limit at what  the 
solar panels are capable of providing. In these installations  the total array was 
divided into 12 banks of 48V sections with panels in series  and parallel to 
make up the arrangement. As the current involved was  considerable the method 
involved was to place a heavy gauge piece of wire after  the solar panel 
breaker and when the bank was activated measure the  resulting current through the 
piece of wire with a calibrated AC/DC clamp type  current sensor and a DVM.
 
With the type of solar panels normally used by hams, probably a  DVM on a 
suitable current range direct across the solar panel terminals would do  the job. 
You have to take care that the panel being tested is isolated from all  other 
power sources such as batteries, but at the end of the day the panel will  
not supply any more than what it is rated to give.
 
Don, KD5NDB was very correct on the need for a blocking diode to be  inserted 
in series with each solar panel when multiple panels are in use,  otherwise a 
panel in shade where the other(s) are in illumination, could  absorb the 
power being generated by back feeding into this panel.
 
Larger sized panels normally have the blocking diode included inside the  
panel assembly or terminal box. In addition they have  internally what I believe 
are called bypass diodes to prevent the  panel limiting the voltage within 
itself when part of the panel is in  shade where the rest is illuminated.
 
Bob, G3VVT