Full Time RV solar and shade

[RollinMadhse]

This is an issue I have yet to work out and I'm curious how others may have solved it. We full time in our TT and I received some solar equipment in exchange for some work. I have 6 120 watt panels @ 17.9 volts for a 12 v system along with a Morningstar controller. (all new in the box) I've had this stuff for 6 months and have yet to install anything because of one issue.

I always see solar installs with the panels on top of the TT or MH and most deal with the losses of flat mounting but nobody talks about not being able to park in the shade. If we park where our TT is in the shade in the afternoons, our ac usage is almost nothing. If we have to park in the sun however, it runs all day. How do you balance the two?

I can see if you had just a could of panels and mounting them so you could place them out in the sun, but even then there are security issues. But with 6 panels how would this even be possible?

Any thoughts?

- Mike

[WheelingIt]

We do it the simple way. We mounted them on our roof and use solar power all winter and fall (where we can comfortably park in the sun) and rely on hookups or shade+generator during the hot months. No way to balance solar and need for AC...the panels simply can't keep up with such a big load.

I've seen folks with less panels (one or two) just leave them outside on the ground and manually rotate/tilt them around to face the sun, but that's not really practical with 6 panels.

[halfwright]

I have 4 150 watt panels flat mounted on my roof. There is about 1 1/2 inches between them and the roof. Last summer, we did not use the AC at all. This summer, we are volunteering and have a free site with all hookups provided, so we have run the AC some in the afternoon€when it was 85+. We are in direct sunlight. I think with air flow under the panels, it acts like a shade and does not get too hot.
I really like our Morningstar converter with the remote readout.

This opinion is worth what you paid for it.

[mgscott4]

I solved the problem by going overkill on the panels. 735 Watts installed in parallel , so if I park partially shaded I still get 200-400 watts peak and 50 -100 watts off peak to charge the batteries back to full charge by afternoon, while still using 140-200 watts for part of the day.

My RV walls get hot from the sun during the afternoon, so I try to park with my right side SW so the awning can help keep the sun off the sidewall.

[RollinMadhse]

I think I'll end up doing the overkill method as well as adding the ability to tilt the panels manually. (although I'm sure I'll McGyver an automated version eventually). I contacted the place the solar panels came from and they will ship me four more from Southern CA to Oklahoma for $720. That will give me 1.2Kw on the roof but will also require a second charge controller. Now the issue is where to put the batteries.

[Shadowcatche]

I went a different route, through ignorance, I mistakenly bought a high voltage panel meant for a grid tie system, this required an MPPT controller. The outcome is that even in shaded sites and from dawn to dusk I am getting usable current. Our trailer is set up to use very little current and we spent eight days in a shaded site on the north shore of Lake Superior and our 150AH battery at the end of eight days was at 65% SOC.

[vsheetz]

I have six 100w panels on the roof, and two portable 100w panels that I set out as needed. Morningstar TS-65 PWM controller.

Here is a write-up I did regarding my choices, installation, etc.

[harleylip]

Originally Posted by vsheetz

I have six 100w panels on the roof, and two portable 100w panels that I set out as needed. Morningstar TS-65 PWM controller.

Here is a write-up I did regarding my choices, installation, etc.

You say you have 6 panels. How many batteries? Zamp solar told me I can not put more than 3 panels, total 450 watts. Or I will burn up batteries ?

[WheelingIt]

Originally Posted by harleylip

You say you have 6 panels. How many batteries? Zamp solar told me I can not put more than 3 panels, total 450 watts. Or I will burn up batteries ?

Errr no. You can put as many panels as you like on the roof regardless of # of batteries. As long as you have a good 3-stage solar charger correctly sized for the # of panels you will be fine. The chrger will charge the batteries until they are full and then no more.

Generally speaking the only thing you "risk" with too many panels is not utilizing them fully. If your power needs are low, then having a bunch of panels might be considered overkill, and if you don't have a lot of battery amps to store the generated charge, then you just kind of waste all that fine potential solar energy. Most people say you should target around 100 watts of solar per 100 amp hours of battery.

That said, I'm of the opinion you can never have too much solar. It helps to have "excess" on cloudy days or with partial shade. We have 440 amphours of battery and 600 watts of solar. It's more solar than we need (we're oversized for our batteries, if you want to look at it that way) but we like it that way. Our batteries get charged fast and we have enough to run everything we want all day long (TV, internet, computers). We never run the generator while boondocking and we do boondock most of winter.

[worleybyrd]

what about the solar panels from harbor fright and can i hook the charger controller right to the batteries that i have in the rv now?

[vsheetz]

Originally Posted by harleylip

You say you have 6 panels. How many batteries? Zamp solar told me I can not put more than 3 panels, total 450 watts. Or I will burn up batteries ?

I have four Trojan 105 batteries - 6 volts each. You can have as many solar panels as you have physical space for them and Your charge controller capacity will handle. This regardless of the number of batteries. With more panels the batteries charger quicker and you have overhead to help mitigate for shaded locations and cloudy days.

For Zamp I think you will find the panel limitation is their charge controller capacity.

[kellylipp]

V & S,

Nice write up and very nice install.

As for the overkill stuff: yes. If you have the real estate on the roof put more up there than you need (within reason). As the serious full timers indicate 600 watts and four T105s is overkill (except when it isn't!). I have 735W and the same battery setup and I'm typically charged before noon in the summers as by mid afternoon in the winter. And we don't do a particularly good job of conserving though we are careful.

Generally you will have some areas of sun and shade on the roof based on where you park. In my case most of my panels "lean" one way so I try to park so they get max sun. But one can't always do that so you get what you get. 1.2KW seems like an awful lot (I wouldn't have had the real estate) but you should never have to worry! You can hook up all those panels to the TriStar and it will simply "clip" the excess amps so the most you will ever get is 60. Or have two charge controllers as you state. That just adds some cost.

For more examples of installs I've got write ups similar to V & S's on my blog:

Kelly's RV Solar Blog | All the Electricity we need and then some!

Thanks,

Kelly

[elkhornsun]

Shading makes it important to wire the panels in parallel and not in series. With series wiring a panel in the shade will block power from all the panels upstream in the array.

What is often overlooked is that if your RV is consuming 50 amp hours of electricity and you have 5 panels with each producing 5 amps it will take only a couple hours to recharge the battery bank. Lots of systems are overbuilt for the RV and it really matters not at all what the output is so long as the batteries are fully charged by the end of the day.

Starting with a good digital charge metering device like the Trimetric will enable the creation of an energy budget with accurate knowledge of how much power is going out and how much is going in at any point of time.

If you are in a situation where the battery bank is not going to be fully recharged each day but only partially recharged before being discharged during the night it helps to have flooded lead acid type batteries as they can better withstand this "abuse" than AGM or gel batteries.

[vsheetz]

For shading mitigation: multiple panels of ~100w wired in parallel and physically spread across the roof.

Tilt-able roof mounts also are typically not rotatable 360 degrees, so consider how often you are going to be able to orient the RV to the south take full advantage of the tilt.

For charge controller sizing laying the panels flat does reduce the realized output from max specification so you can take this into consideration. For my 100w panels optimally angled on a good sun day in an optimal month at my home location I can measure a panel at ~6a to 7a, then laid flat on the roof the best I see is around ~5a. You can do some modeling with PVwatts to see the tilted to flat orientation difference.