Solar panel questions

[Mex-Busnut]

Dear Friends:

I am always asking a trillion questions. I certainly appreciate all of your input!

I am checking into solar panels for our bus and am wondering what is better (These are the types available down here in Mexico.):

1. Mono cristaline

2. Mono cristaline

3. Has anybody used a PWM brand controller for your solar system?

http://articulo.mercadolibre.com.mx/MLM-422487598-controlador-regulador-de-carga-solar-30amp-panel-1224v-_JM

Thanks in advance!

Steve

[Uglydog56]

I am not an expert.  I haven't even finished my install yet.  I've just read lots of stuff.

Mono vs poly crystalline (I think that's what you meant).  Mono is supposed to be a little better, but more expensive.  Just buy what you get the best dollars/watt deal on.

If you use 12v panels (which are actually 17v panels) on a 12v system, or 24v (35v) panels on a 24v system, a PWM controller is supposed to be just fine.  I didn't look at your link.  They can actually be more efficient than an MPPT controller when input/output voltages are matched.  If you want to run your panels in series, or use higher voltage panels like I did (I'm using 35v panels on 12v system), then you need an MPPT controller.  Bigger systems should probably use an MPPT controller.

[Uglydog56]

This guy writes fairly clearly, and has lots of information.

http://www.jackdanmayer.com/

This guy was not an english major, but it's still worth reading.

http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/

[bobofthenorth]

Do a lot of reading before you start buying.  I think there are a lot of good reasons to use an MPPT controller but my reasoning has nothing to do with differences in efficiency between MPPT and PWM controllers.  With an MPPT controller if you use identical panels and wire them in series on your roof then you can use smaller gauge wiring to get down into the bays.  That can be a big saving on wire cost and more importantly it is much easier to snake smaller gauge wires down from the roof.  MPPT also lets you use higher voltage panels.  For the installation I just completed on the boat I used 3 x 230 watt panels which are open circuit 36 volts each.  Under normal operating conditions I see input voltages running from 100 to 120 volts and on the rare sunny day in BC I'll see a little over 30 amps into a 12 volt battery bank.