For charging a 12V RV battery bank via a Classic 150, I'm assuming that higher voltage panels (20V nominal) will be better at charging my battery bank than lower voltage (12V nominal) -- is that right?
I would say yes to the 20 V nominal panels. A bit higher voltage than the nominal battery voltage is almost always better than a lower, and possibly too low voltage of PV module.
A 12V nominal PV will, a lot of time, be too low if it gets hot. Then, there is the wire loss part of it all that can be made better by upping the input voltage a bit.
boB
Quote from: zulu on November 05, 2011, 06:20:41 PM
For charging a 12V RV battery bank via a Classic 150, I'm assuming that higher voltage panels (20V nominal) will be better at charging my battery bank than lower voltage (12V nominal) -- is that right?
Make sure your panels have air space below them. A slight tilt will allow convection to carry away the heat much better. If you run the panels in series your array will have a higher voltage, the Classic will do wonders with the amps going into your batteries. Another consideration is your wire. Running parallel wired panels means big wire unless you have only a couple of panels up. For an RV every watt/amp counts. We use #1/0 wire to everything. Sure it costs more to do that but solar in an RV isn't about saving money.
The numerical definition of high voltage depends on the context of the discussion. Two factors considered in the classification of a "high voltage" are the possibility of causing a spark in air and the danger of electric shock by contact or proximity. The definitions may refer to the voltage either between two conductors of a system or between any conductor and ground.
In electric power transmission engineering, high voltage is usually considered any voltage over approximately 35,000 volts. This is a classification based on the design of apparatus and insulation.
actually, the nec does consider anything over 50v to be high voltage and they handle it slightly different.
For my purposes, anything over 12V nominal is high voltage.
I would go for higher voltage for your Panel strings, will get less power loss (I^2R losses), being from OZ we have rules can work upto 120 volts DC being unlicenced, not sure of your NEC rules.
My 2.2kW array feeding a classic 150 as 3 190w panels in series by 4 strings
Regards
Frank
thanks for all these safety ideas... I think you should go for higher voltage for your Panel strings for better output.