Posted by maui on January 26, 2009, 12:13 am
I have 4 x 48 watt panels on my boat that were made in 12/89. I put
them on the boat in early 1990 when they were new. I am wondering
about their current output and if I should replace them. The panels
are marked 2.88 A optimum current and 16.7 V optimum voltage. Those
numbers produce 48.0 watts. Seems like I'd need a 5.8 ohm 50 watt
resistor? New panels give quoted Isc - short circuit current. How can
I test my panels with a multimeter to see if I should replace them?
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Posted by Blue Cat on January 26, 2009, 2:08 pm
Best way is to test the panels under load. I use a set of power resistors,
or a rheostat. As you approach the panel's maximum power, you will need a
resistor rated 50 watts.
Posted by Eeyore on January 27, 2009, 2:19 am
I can't fault your calculations but the nearest 'standard value' resistor
is 5.6 ohms. It shouldn't make much difference in practice. The resistor
will need to be rated at 50 *in free air* or it will need heatsinking.
You'll also need a 'calibrated day' to check their output. This may prove
more problematic. ;~)
New panels should also give optimum values. Suggest you shop elsewhere or
google the data.
Posted by Martin Riddle on January 27, 2009, 2:47 am
Easiest would be to check Open circuit voltage and short circuit
If its close to the original panel rating then your good to go.
Posted by BobG on January 27, 2009, 7:54 pm
DC clamp on ammeter, voltmeter, and a calculator?