90 watt PV = 3.25amp output??

[VisualMonster]

So, I have my two 45 watt (HF) panels hooked up in parallel charging a 12v battery array.

The batteries are 6v and I have six of them total.

When I tested the current generated by the panels, it is showing 3.25 amps.  At the time, my battery was at 12.65 volts.  I figured 3.25 amps * 12.65v = 41.11 watts.  Seems a lot lower than I expected.  Both sets of panels were fully exposed to pretty good sunlight at the time.

I did a simple test to make sure both panels were properly hooked up.  I covered both with large towels and checked the charge controller.  The LED was OFF as expected.  I then uncovered part of the panel at a time (exposing only single panels at a time (each 45watt array consists of 15w smaller panels).  Each time I exposed a single panel, the LED was ON. So, all my panels must be properly connected.

Is 3.25 amps @ 12.65 volts normal output?  Maybe watts are calculated using open voltage?  If so, then it would be 3.25 amps * 23.57 volts = 76.6 watts.  That seems a bit closer, especially considering sun wasn't angled exactly perfectly (but it was pretty close).

thoughts?

[sk windpirate]

You are in the ball park. 90 Amps of pannel should give about 6 amps. "IF" all the stars are aligned right and the sun gods are on you your side.

you could try using some reflective material around your pannels. tilt them in toward the pannels. that will help some. make sure they are directly facing the sun. (both angles) that will help also.

the factory mesured amps are for the best of conditions. If you ever get it "record it" it won't happen often.

[Flux]

The 90W should be at the peak power point which is typically something like 18v.

It is measured at 1kW/M^2 insolation, which you may not see very often and at a temperature of 25degC. Most likely you will have the panels warmer than that if you do see that insolation level.

Also with some manufacturers this figure may have been obtained from the best of a batch.

Better manufacturers expect each panel to meet the spec.

On a very cold clear and sunny day, I see 5A from a 90W panel, it won't make that in the summer.

You are still a bit on the low side so check your wiring resistance and also watch it for a few days, you may not have the best sun conditions yet and you might not have the panels square on to the light.

Flux