slightly different solar qx
Am looking at solar on a small class A. I currently have 3 group 27 batteries (rv/marine) for the house. (prior owners had just installed 2 new, and I had one from a trolling motor setup) they will...
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A note on PWM. Vmp and Imp have no meaning except for the panel's rating in watts. Your Voc and Isc are what matters.
If the panel is 22 Voc and 6.3 Isc, you set it out in the sun and the panel heats up, losing voltage, so you might see 20 Voc if you took a reading. If you took the Isc reading that will be the amps you see out of the controller given decent wiring. That amps figure will vary all day as the sun rises and falls. You can see 6.3 amps at high noon, eg.
The lower voltage in the heat does not matter with PWM so it is fairly meaningless too. However, the lower voltage in the heat does matter with MPPT, where it is all about Watts.
Your 325w panel will lose about 10% of its watts with the panel about 25C above 25C at 50C. See the spec showing about 44C panel temp. You can't use the 325w rating for anything in most cases, because that is for 25C panel temp, which means it must be near freezing ambient.
If you have an IR gun and the panel is tilted up, you can check its temp on the back side of it. Use the spec they give for how much voltage it loses per heat, and you can then compare that with the input watts displayed on the controller. ( but only if you get the urge :) )
If the panel is 22 Voc and 6.3 Isc, you set it out in the sun and the panel heats up, losing voltage, so you might see 20 Voc if you took a reading. If you took the Isc reading that will be the amps you see out of the controller given decent wiring. That amps figure will vary all day as the sun rises and falls. You can see 6.3 amps at high noon, eg.
The lower voltage in the heat does not matter with PWM so it is fairly meaningless too. However, the lower voltage in the heat does matter with MPPT, where it is all about Watts.
Your 325w panel will lose about 10% of its watts with the panel about 25C above 25C at 50C. See the spec showing about 44C panel temp. You can't use the 325w rating for anything in most cases, because that is for 25C panel temp, which means it must be near freezing ambient.
If you have an IR gun and the panel is tilted up, you can check its temp on the back side of it. Use the spec they give for how much voltage it loses per heat, and you can then compare that with the input watts displayed on the controller. ( but only if you get the urge :) )
