a newbie's questions for RV solar setup

hsquared

I'm setting up a solar power system on my converted RV. I'm slowly learning about it from miscellaneous posts and forums. Here's the system I am considering:

After completing the energy use worksheets, I will need roughly 1200 Total Watt hours in an area with five hours of good sunlight.

Based on a kit sold by http://partsonsale.com/campers2.html, I will need:

[*]2-130 watt Kyocera panels
[*]MPPT250 250 Watt high efficiency Multi Power Point Tracking charge controller
[*]25 ft of sunlight resistant wiring,
[*]Two MC4-5 cables
[*]25 amp inline photovoltaic fuse

I currently have a 375 watt inverter (don't have too many appliances to run).

For batteries, I am thinking (2) Trojan T-105 6V 225Ah Flooded Lead Acid GC2 Deep Cycle Batteries. Is this overkill?

As far as the correct wire gauge to use, I am unsure. I will need 6-8 feet of wire from the solar panels to the batteries, so what gauge will I need for that?

What's a good monitor for this system?

If anyone has any suggestions for this setup, I'm all ears.

Thanks a bunch!!!!!!:D

mike95490

Re: a newbie's questions for RV solar setup

hsquared wrote: »

I'm setting up a solar power system on my converted RV. I'm slowly learning about it from miscellaneous posts and forums. Here's the system I am considering:

After completing the energy use worksheets, I will need roughly 1200 Total Watt hours in an area with five hours of good sunlight.

Not knowing how you calculated this, I'll assume you included 20% PV panel derate, 20% battery charge loss and 20% inverter losses, and that your 1200Wh means you consume 600Wh ?

1200 / 5 hours = 240W harvested per hour, and fed into the batteries.

To harvest that much, your chosen 2 panels will fall short, being flat on the roof, their 260W nameplate will at least fall to 208.

What is your LOAD consumption ? Double that, and that is what you have to harvest over the course of a day.

2, 6V batteries in series is a good choice, better than 2, 12V in parallel. Series solves some current sharing problems that exist in parallel systems.

niel

Re: a newbie's questions for RV solar setup

welcome hsquared,
one very bad thing on your list is a bz controller and they are junk. there are many other controllers to choose from.
http://store.solar-electric.com/chco.html
also, think about pricing some of the other stuff from our host.
http://store.solar-electric.com/
even some 2nds or blemished pvs are at sunelec.com
you have lots of choices, but that controller you should stay away from. be sure that you get a battery temperature sensor for whatever controller you buy.

BB.

Re: a newbie's questions for RV solar setup

A couple of suggestions... Stay away from any BZ charge controllers. They do not have a good design or history (at least others we have seen).

Get a name brand charge controller instead (PWM if you are trying to save some money. An MPPT if you are looking to gain ~10% power in cold weather charging--is great for larger installations with long wire runs between the panels and the controller--not so much needed for smaller systems with short wire runs). Also, get a charge controller that supports a remote battery temperature sensor (and get the sensor if it is optional). Will really improve your overall battery charging (and it pretty much required for some controllers for proper charging operations like the MorningStar MPPT 15 amp controller).

Are you up in British Columbia? If so, you can probably get some real improvements is power collection with your solar panels if you can tilt them up (especially in the winter for you).

From the PV Watts solar website... Assuming 260 watts of solar panels (I will enter 2.6kW and move the decimal point to the left one place--1kW is minimum for program). Assume 0.52 derating factor (for off grid with inverter) and flat vs tilt to latitude settings for panel for Vancouver BC:

[FONT=Fixedsys]Results for 49 degree tilt

Month
Solar Radiation(kWh/m2/day)
AC Energy (kWh) per month
Energy Value (Can$ @0.0862 Can$/kWh)

1      1.41          5.4     0.465 
2      2.69          9.9     [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]853 
3      3.44          13.9    [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]1198 
4      5.13          20.4    [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]1758 
5      5.43          22.0    [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]1896 
6      5.25          20.0    [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]1724 
7      6.03          23.6    [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]2034 
8      5.60          22.2    [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]1914 
9      5.04          19.7    [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]1698 
10     2.72          10.8    [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]931 
11     1.68          6.4     [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]552 
12     1.32          5.2     [/FONT][FONT=Fixedsys]0.[/FONT][FONT=Fixedsys]448 
======================================
Year   3.82          1797   $15.49 [/FONT]

Now the same thing with tilt=0 degrees (flat to roof)

[FONT=Fixedsys]Results for 0 degree tilt

Month
Solar Radiation(kWh/m2/day)
AC Energy (kWh) per month
Energy Value (Can$ @0.0862 Can$/kWh)

1      0.80          2.1     0.181 
2      1.58          5.0     0.431 
3      2.66          10.4     0.896 
4      4.57          18.2     0.1569 
5      5.62          23.1     0.1991 
6      5.98          23.3     0.2008 
7      6.56          26.1     0.2250 
8      5.30          21.1     0.1819 
9      3.89          14.9     0.1284 
10     1.77          6.3     0.543 
11     0.94          2.7     0.233 
12     0.64          1.5     0.129 
======================================
Year   3.37          154.6     $13.32[/FONT]

During the Summer, you will actually collect more power with the panels flat--but during hte winter, you will collect almost nothing with them flat. And tilting them near vertical will help them shed snow too (if snow camping and/or used to keep the batteries charged during the winter months).

Note that the monthy kWhr figures are PER MONTH. For per day, you will need to divide them by 30 days per month.

-Bill

mike95490

Re: a newbie's questions for RV solar setup

Don't forget to secure movable/tilted panels before you drive !