In a message dated 22/06/05 15:26:09 GMT Daylight Time, [EMAIL PROTECTED] 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 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
