Solar Panels 'flat' on roof??

Hello Signman,

for a solar panel mounted on a vehicle which constantly changes directions, it's a no brainer to put it flat on the roof.

The only way to improve the solar output in such a situation is to have the panel mounted on a 1 or 2 axis solar tracker.

But the power gain from the panel when doing this will most likely be gobbled up by the added wind drag of a tilted panel, and by the tracker motor(s).

So keep it flat while travelling, and tilt it at latitude angle and make it facing north when stationary.

Best regards, Peter

Signman ,

Yep correct the 3 hours around midday would be the max - after that the input would drop off rapidly until sunset when almost nil.....

I have a 140 watt mounted flat on the Jeeps roof rails and it runs a 100 aH AGM which in turn runs my Waeco 50 - If I get 4 cloudy days in a row I need to get to 240v pretty quick to top up the battery - If its sunny days then no problems --
I don't have a dual battery setup yet and so far ( touch wood ) haven't really needed one ... However the Kimberley trip next year will cause me to fit one before leaving I think...

Cheers

Steve

There is a formula for the losses from flat as against angled. It is much cheaper to add more panel watts than make angular from my enquirers.
I have mine flat and no problem. just need to work it out before you start.

Neil

I know a bloke that had solar panels mounted on an aluminium rack on his car. The rack sat flat, but with the pull of 2 spring loaded latches the panels would lean forward to 15 deg or whatever the optimum is. He had gas struts set to get the right angle. He also had an in-car compass to ensure he could park facing North.
He had a battery in the van & a couple in the back of his ute & a fair length of lead to join the solar panels & bank in the car to the van.
It is one of the best set-ups I have seen. But wasn't cheap

Why worry about Solar Charging when you're driving - a Panel puts out 5 amps - your Alternator can put out 50 amps at least !

Hi I have mine flat on the roof. They are also hinged so I can raise them to 45deg if I need to catch more sun in the PM when stopped. I also plug the
Engel's into the car when travelling.
Brian

Whilst panels may loose quite a bit of output at midday when lying flat as compared to the correct angle, you can not use this to calculate the efficiency drop over the whole day. In the morning and afternoon flat mounted panels will put out more than they do when elevated in the optimal position (particularly when the sun is below the east/west line.) Thus they do not loose as much output when mounted flat as they appear to if you only look at the midday results.

As suggested previously in this thread - just increase the size of your panel(s) a little. That will be cheaper and less fiddly than providing moveable mountings or trackers.

I have 2*80 watt panels mounted on a tripod with a suntracker system. They are rated at 4.5 amps delivery each, with the tracker I can get 9.3 amps from both all day while the sun is out and if the sky is overcast and thin it will lock onto the brighter areas and still produce up to 3.5amps. Its a bit difficult to use on the move but if you have about 40_60 amps from the alternator you don't need solar. Barnray

signman,
It depends on the performance characteristics of the panels, some will work much better in low light conditions than some others and therefore they also start delivering current into the battery much earlier than the less efficient panels, this gives you much better battery charging overall.

My system gives 100% of it’s rated output before 11.30am even when laying horizontal on the roofrack.

Maîneÿ . . .