I've read most of the numerous install threads related to the subject but wanted to start my own:BI'm in the beginning planning stages and want to start with panel selection so I'll just start by asking some questions.How should I decide whether to use 12v or 24v panels?Any brands better than the others or is it just a "you get what you pay for" thing?Are there different "types" of panels that are best for RV use.Where is the best place to buy your panels?Is a tiltable bracket worth the extra expense?Is their a preferred off the shelf mounting system or can I buy most of the parts from my local Home Depot?That should be enough for now, thanks in advance.Kevin

What would you like to be able to do with your first solar set up, and your eventual complete set up?A lot of the answers you will get (from myself included) will tend to make implicit assumptions about that, so it is better to get what you know about what you may want to do out there early.I don't know yet is a valid answer, if you are just in the exploration stage.Jim

12V or 24V depends on how much roof space you have, how much solar you want and how much your budget is. As far as brands, IMO, solar is cheap enough that brand doesn't matter. Very few are going to exercise a particular panels warranty before selling their rigs. Being in CA, solarblvd.com in Norco is the "best" place to buy panels IMO. You are a ways away from there but you might still want to weigh the shipping costs vs driving down there and picking them up.

Renoman69's install compilation thread is a good one. Also, Jack and Dan Meyer's website has a lot of good information.I bought my module from Solarblvd.com and am happy with everything except the shipping cost, as Mena noted.Potential amount of solar charging power is hinged on battery capacity and daily use, for the most part. Living in sunny CA helps. If you haven't done an energy audit, this downloadable spreadsheet, posted by Pianotuna, is a really good way to estimate needs and battery capacity. I chose a 24v nominal 235w module and a Morningstar MPPT controller for my needs. The controller can set charging parameters through the optional PC software interface and also shows real-time data from the system. It is geeky as H&^%.

When solar panels where over $5 per rated watt, and a 90 watt system with controller, wiring and wiring diagrams cost $750, the extra $20 for tilt brackets was worth it to get the extra 15% in power IF you stay in one location more than a few nights. (going sightseeing with the RV each day meant that this was no longer a advantage).Now that you can buy solar panels for around $1 - $1.50 per rated watt, it is not worth it to tilt the panels. Just buy another 100 watts, and not worry about climbing onto the roof.I made my brackets with 2" angle aluminum. I cut it at 6" long and drilled 1 - 5/16" hole for the bolt into the panel frame, and 3- 3/16" holes for #10 screws into the RV roof with a lot of RV roof sealant.Tilt arms where made from 3/4" thin gauge aluminum about 18" long.I used 1/4-20 "Nutserts" that pop rivit into the solar panel frame. I used stainless steel tamper resistant bolts into the panels, to keep them from walking away.I used #10 - 2 UV resistant grey romex running down the refrigerator vent to the controller, it is good for about 15 amps each run. If you have more than 2 panels, run two wires. (Home Depot) If you have 4 panels that are identical, you can pick to run them at 24 volts IF you have a MPPT controller. MPPT controllers can take in up to 60 or some models 150 volts and convert it to 12 volt "Nominal" output. Then you will have less voltage loss through the wiring.I have my system set up with 12 volt nominal voltage - the panels put out about 21 VDC. This goes to a 50 amp controller that puts out 13.5 volts to recharge the battery. I have a pair of golf cart batteries. My first pair lasted 13 years and I gave them to a friend who kept using them. My second set only lasted 6 years, I forgot to add water a few times. SunElec.com has panels from $1 per rated watt. Look for 12 volt panels if you want to use PWM controller, or any voltage if you want to use a MPPT controller. I just bought a couple of 10 amp PWM controllers for $13 each. AliExpress.comSolarOnSale.com is where Ihad my Trace inverter repaired in 1999 and bought my pair of 120 watt panels. THey also do installations in Victorville CA.Fred.

What the Hitech said. Decide what you want from the system first. Some people need 5 times more a day, than others. You can't just "decide" between 12V and 24V. Small panels are mostly 12V, and larger ones, say, over 180W - 24V. It can be easier to mount a few panels under 120W each (and then they will be 12V, you won't have a choice of voltage here) - than one panel over 200W (which will be 24V or higher) but there are drawbacks to either scenario. It's too early to talk about this. You need to decide how much total wattage you want.

Yet another Solar Install thread | Good Sam Community

37 Replies

Almot
Explorer III
Jun 28, 2013
full_mosey wrote:
The big problem is that those residential energy ratings are based on normal indoor air-conditioned 72F conditions

... and on proper ventilation space around the fridge, which isn't always the case with RV.
full_mosey
Explorer
Jun 28, 2013
The big problem is that those residential energy ratings are based on normal indoor air-conditioned 72F conditions.

If you are going to camp in cooler locations, then you could use those ratings to estimate energy use.

What will be the temp ranges that your fridge will experience? That will dictate your energy needs.

HTH;
John
Almot
Explorer III
Jun 28, 2013
It doesn't have to be tiltable if only occasional access is needed. There is very popular design with on 2" aluminum angles and 1/4" machine screw through the side frame of the panel. Can be with rivet nut in the frame or a locknut instead. Like Mr Wiz installation. You make the brackets 4x4 instead of 2x2, or drill the holes in the frame 1" from the corner. Then remove 2 screws on the side that you want to lift, and it will rotate on the remaining 2 screws just fine.

I think his is a motorhome, so you might want to look into it more. Fiberglass roof of motorhome is not the same mounting platform as a rubber-coated particle board of travel trailer.
mena661
Explorer
Jun 27, 2013
I find that 175W panels are not much smaller than a 235W panel. It seems that much over 140W and you might as well get the bigger panel. Roof space varies. I barely have space for two 235W panels on my MH (why I'm looking for one big panel like 280W or something currently). On my "old" 5er I had plenty of space for 3 235W panels.
Golden_HVAC
Explorer
Jun 27, 2013
McKenziek wrote:
Lot of good replies and much appreciated. My goal is to be able to run my 18 cu ft residential refer without having to use my propane generator and occasional use of the microwave. I have 2 Trojan T105's with plans to get two more. I will take a look at Pianotuna's load spreadsheet, that should do the trick.

That large of a load will take a lot of solar panels.

You can start out with 4 each in the 100 - 175 watt range. Larger than 175 watts, it is really not something that you can locate on a RV roof, and still be able to pass by it when cleaning the roof, or making repairs.

You really do want it tiltable, in case you need to tighten the wire connections, or repair the roof.

You really need to have it about 1" above the roof, so cooling air can get under it. Solar panels produce much less power when hot.

Fred.
Almot
Explorer III
Jun 25, 2013
McKenziek wrote:
I meant that the Motorhome is not at home so I cant check the power rating on the fridge

Not important. Mena is right, latest $$ 120V units can draw around 1KW=80AH a day (if it works as it should). Since you plan to have some genny time every day, it doesn't matter - too much - whether your frig draws 1 or 1.5KWH a day.
mena661
Explorer
Jun 25, 2013
Almot wrote:
L16 are very good batteries if you have a friend with a forklift ;)
I have one! Oh wait, that's me. :(
McKenziek
Explorer
Jun 25, 2013
Almot wrote:
McKenziek wrote:
I wont run the Micro on inverter. I dont have the unit nearby where I can see the load rating

+2,000W inverter will never be "nearby" - it has to be very close to the battery. Forget that voltage display on the inverter. For watching loads people use standalone watt-meters or battery monitor like Trimetric.

Agreed with other posters - 120V fridge is what makes generator-free life impossible. It draws less current than MW but for much longer time, over 24 hours it will consume more than all your other items. MW is bad only because it draws high current and therefore requires costly inverter.

I meant that the Motorhome is not at home so I cant check the power rating on the fridge
Almot
Explorer III
Jun 25, 2013
L16 are very good batteries if you have a friend with a forklift ;)
Almot
Explorer III
Jun 25, 2013
McKenziek wrote:
I wont run the Micro on inverter. I dont have the unit nearby where I can see the load rating

+2,000W inverter will never be "nearby" - it has to be very close to the battery. Forget that voltage display on the inverter. For watching loads people use standalone watt-meters or battery monitor like Trimetric.

Agreed with other posters - 120V fridge is what makes generator-free life impossible. It draws less current than MW but for much longer time, over 24 hours it will consume more than all your other items. MW is bad only because it draws high current and therefore requires costly inverter.