MrWizard wrote:
you guys think its a safety "derating" tell the consumer to use 3xx max panels
and he can't possibly hit the controller limit
Okay could be ..
BUT ??
other controllers some costing more some about the same
are built with heat sinks and current limiting, and simply clip any over current and pass thru the rated limit..these controllers are truely what they say they are
i dont think a user should have to buy a 45amp controller to control 30amps worth of panels
or a 30amp controller to control 22amps worth of panels
just build it for what it is supposed to do and price it accordingly
I have a 150W solar panel 12v kind. It is rated lsc of 8.8 amps. My RC charge meter has recorded a peak amperage out of that panel of 9.3 amps, on a 65% SOC battery. I'd have no problem putting 2 panels together, but there is no way I'd run the two through my 20 Amp Charge controller that I also use, too close for comfort. I probably would run a pair of 140W panels through the same 20 amp charge controller and not worry of the blue smoke syndrome.
For $33 for a 30 amp charge controller, even if it's 24 amps, derated, go try and build and sell what you want... I am sure there are some high roller RV'ers that will buy bling to show off to their RV buddies. There will also be the low budget travel trailer and camper folks looking to charge cheaply with a value priced charge controller. Pick your price point, and market accordingly.
My thought process it that by the time the sun is at it's 10 AM position, where the panel can make max amps, your batteries are probably at the point where the amp charge rate is dropping off as the voltage increases, if you designed a balanced proper battery pack, solar panel and charge controller system that is properly designed and integrated. That, in essence, lets the marketing people able to cheat a bit on the ratings, most of the recharging is done when the panels aren't aimed directly at the sun, so the panels aren't maxing out until later in the day... at that point the charging rate of the batteries is lower, they are chemically reducing the amount of amps accepted at that point and state of charge.
