tecnodave's thoughts on tiltable panels, over-paneling and use of the Midnite Solar "Kid" MPPT solar charge controller vs PWM controller (incl soon to be released "Brat") in an rv:
"Over paneling depends on many factors, in my case I have enough to make it through several days of fog without running a generator to top batteries. A kid at 24 volts can safely handle 800 watts but I have seen 942 watts from one kid on my motorhome with 1020 watts of panel. It was maxing out at 30 amps. That is a bit over paneled. To be more conservative of my equipment now I am using two kids to power motorhome. 1020 watts on two kids is very conservative but I can run on one alone if need be. I have installed extra breakers so system can be two separate controllers or bully mode or follow me mode.
The main panel racks for the motorhome covers the entire roof except the cab over area. The rack is built from awning arms mounted to the roof so that they can tilt to left or right. they are 7' X 8' each and mount three Sharp 170 watt poly panels in top row in portrait orientation and four Siemens 55 watt mono panels for the 12 volt system in landscape orientation on each half.
I have a total of 1460 watts on the roof and an additional set of Suntech 280 watt panels 560 watts total on a ground mount for a total of 2020 watts in.
This motorhome is not used on the highway........it lives in the country as a mobile house....maybe moved twice yearly. This is not a huge motorhome....it's a Tioga Class C 24 foot on a Chevy van C-30 chassis. Main battery set is 500 pounds and standby is 250 pounds.
I just love the kid controller, in the past I had used a MPPT controller that could not be set to match the battery set. That caused me to have to top off the batteries with the generator set which is the most wasteful time to use the gen but the non adjustable controllers just cannot top off anything but the most common batteries. I almost ruined a good set of L-16's using non adjustable controllers and at this point if I cannot set every value to fit my system then I don't want to mess with it. The Brat comes from good lineage but it is limited in that it is not adjustable. I'm sure that it will have a better charge profile than the competition which is Chinese or the Chinese Morningstar.
I'm using an old standard PWM controller on my 12 volt system rather than newer MPPT controller because the old Trace C-40 can be set to the voltage I need and my much newer and more efficient Chinese Tracer MPPT controllers can not be set. They leave the battery at 1.220 s.g.... To me that is dead! I want to see 1.265 s.g.
I am a technologist and I need to control my entire system to the nth degree....I need a lot from it
I demand a lot from it.....I built it!
I think that if I had a retail Kid with 600 watts of panels on a 12 volt system that I would be sure that the Kid has plenty of ventilation and maybe set the current limit down to maybe 25 amps or so unless you really need all that power, in that case two kids teaming together would be way more conservative design and would be more reliable in the long run as you would not be running at max all the time.
If the panels are flat on the roof then 600 watts panels corrected for angle would be more like 400 watts output max so one kid can handle that without a problem. I don't like the idea of running at max power for extended lengths of time, it does not lead to longevity.
td"
from:
http://midniteforum.com/index.php?topic=2108.15