First solar build in my camper

[JamesRich]

I've always been interested in solar but never built a system. I've decided to try a build in my camper first. It came with the generator prep so it has a large compartment in the front where a generator would go and a transfer switch already wired in. I've started with a Renogy 3000w inverter wired to the transfer switch running off of two deep cycle batteries setup as 12v and it's working great. I've ordered 4 LiTime 100 amp hour batteries to replace the deep cycles. That's as far as I've gotten. I'm planing on 8 100 watt Renogy flexible panels for the roof and 2 Renogy 40 amp MPPT charge controllers. I know a 48 volt system would be more efficient but I'm keeping the system 12 volt because everything in the camper runs on 12 volt. In the cooler months I won't need the inverter except for microwave or coffee pot etc. A question on wiring the controllers, Renogy states their 100 watt flexible panels have a operating voltage of 18.9. I'm planning to run 4 panels on each controller. would it be better to series all 4 for a input voltage of 75.6 or series pairs then parallel them for an input voltage of 37.8? Is there a loss from larger voltage differences like with inverters?
James

 

[Tomthumb62]

I've always been interested in solar but never built a system. I've decided to try a build in my camper first. It came with the generator prep so it has a large compartment in the front where a generator would go and a transfer switch already wired in. I've started with a Renogy 3000w inverter wired to the transfer switch running off of two deep cycle batteries setup as 12v and it's working great. I've ordered 4 LiTime 100 amp hour batteries to replace the deep cycles. That's as far as I've gotten. I'm planing on 8 100 watt Renogy flexible panels for the roof and 2 Renogy 40 amp MPPT charge controllers. I know a 48 volt system would be more efficient but I'm keeping the system 12 volt because everything in the camper runs on 12 volt. In the cooler months I won't need the inverter except for microwave or coffee pot etc. A question on wiring the controllers, Renogy states their 100 watt flexible panels have a operating voltage of 18.9. I'm planning to run 4 panels on each controller. would it be better to series all 4 for a input voltage of 75.6 or series pairs then parallel them for an input voltage of 37.8? Is there a loss from larger voltage differences like with inverters?
James

I’m sorry to hear you’ve ordered Renogy’s stuff. I wasted so much money on their junk. I just replaced the last renogy device and am glad to be done with it. They look sexy, nice price and specs are good on paper and they sometimes perform okay but I wish I had not wasted so much money. The good part is that the public has been duped into thinking Renogy is good quality and is paying good prices for used. So I will sell my final renogy device for at not much loss. They have an excellent marketing campaign.

That said, the one renogy item I still have that’s decent is the folding 200W suitcase with rigid panels.

For my money, I think the flexible 100W panels by Sunpower are much better than the flexible renogy ones, not too much more expensive.

That said, have you done an energy audit? That 3000W inverter might be overkill for your actual needs, depending. It has a large idle draw.

 

[Doggydogworld]

That said, have you done an energy audit? That 3000W inverter might be overkill for your actual needs, depending. It has a large idle draw.

It takes a lot to start one of those camper air conditioners, e.g. a Dometic 13.5k BTU rooftop unit.

 

[JamesRich]

Yes I was impressed with renogys adds but I also have their 2000 watt inverter in my service truck for two years now & it’s run everything I’ve needed on the truck even a microwave so I don’t have cold lunches when I’m out in the middle of nowhere! I’m a mobile heavy equipment mechanic. The 3000 watt I put in the camper already starts my main A/C with no troubles. It’s a dometic 15k. I put soft start caps in it a few years ago so I could run it on a small generator. The inverter and 4 batteries is all I’ve bought so far. I’ll check out sun powers panels. What do y’all suggest for charge controllers?
James

 

[MichaelK]

Well, I wanted to be the first to dissaude you from buying more Renogy, but TT62 beat me to it. Couple of suggestions. If you can, avoid buying more 100W/12V panels. If the roof-space will allow it, you'll bet more bang for your buck going with larger, high-voltage residential panels (grid-tie style).

Here is someone selling mostly 60-cell panels in the 50-60$ range. Take a look at their dimensions and see if you can make them work?

Used SOLAR PANELS, $50 to $75.... - materials - by owner - sale - craigslist

Lookin' for some cheap solar power? Got em! Full semi-load of used residential-size solar panels, from 210 watt up to 305 watts, several different manufacturers including REC, LG, Yingli, Trina...

nashville.craigslist.org

Here is a voltage drop calculator to determine how much power you'll lose going from one wiring configuration to another. Keep in mind that you'll need factor in cold-temperature compensation for determining what your voltage string will be. I'd guess in Tennessee, you'd need to use at least a 1.18X conversion factor, which I think is for ~zero degrees? That means an array putting out 75V at room temperature will be putting out 88.5V in zero-degree weather.

Really, I consider a 12V, 3000W inverter to be a scam product. You will NEVER see that inverter actually produce 3000W! One potential option is to go with a higher system voltage to just power the inverter, but leave it off most of the time, and run your 12V stuff on 24V to 12V converters.

 

[JamesRich]

I’d rather the flexible panels so I don’t have to drill holes in my roof. I’m planning to run the wires down the refrigerator vent. I switched to a 12 volt fridge already so the vent isn’t doing anything.
This will be my first solar install but I’ve installed inverters before. Here’s my service truck with the 2000watt inverter. It powers my microwave, battery chargers for my Milwaukee tools, corded tools, even a 24 volt battery charger to jump heavy equipment. Also ran power in the cab to charge my laptop. I could run these things off the welder but it’s less trouble to use the inverter.

 

[chrisski]

I'm planning to run 4 panels on each controller. would it be better to series all 4 for an input voltage of 75.6 or series pairs then parallel them for an input voltage of 37.8? Is there a loss from larger voltage differences like with inverters?

IMO for a camper, as many on the roof in parallel as possible. Often parking is partially shaded, and a single panel shaded can bring the string down by 75%.

 

[Tomthumb62]

Flexible panels get little love on this forum, because yes rigid is better. And a lot of forum members aren’t mobile and don’t see the upsides of flexible panels.

Unless you go for the military grade $800-per-100W-panel, the Sunpower ones are the best out there for the money.

We bought from Sunpoweredyachts.com and used coupon code “RVwithtito” for 10% off. Free shipping. Comes to about $160 after tax.

Also, have you seen RVwithtito’s YouTube channel? Good videos for the rv crowd and solar. I highly recommend watching and using his latest no drill flexible panel install method:

This adds needed cooling for flexible panels and provides a secure way to mount them. There’s some added expense with the rails and corrugated plastic, but it’s worth it if you don’t want to drill. Eternabond and other strong adhesives can be removed by scraping and goo gone.

 

[chrisski]

Flexible panels get little love on this forum, because yes rigid is better. And a lot of forum members aren’t mobile and don’t see the upsides of flexible panels.

Unless you go for the military grade $800-per-100W-panel, the Sunpower ones are the best out there for the money.

We bought from Sunpoweredyachts.com and used coupon code “RVwithtito” for 10% off. Free shipping. Comes to about $160 after tax.

Also, have you seen RVwithtito’s YouTube channel? Good videos for the rv crowd and solar. I highly recommend watching and using his latest no drill flexible panel install method:

This adds needed cooling for flexible panels and provides a secure way to mount them. There’s some added expense with the rails and corrugated plastic, but it’s worth it if you don’t want to drill. Eternabond and other strong adhesives can be removed by scraping and goo gone.

I don't recommend this install.

I Did this very same install on a rubber roof. After a couple of months, the tape started to peel the rubber off the roof, making a sort of bubbling. Wind must get under those and vibrate them.

Now, when I install these flexible panels, I tape all four sides completely down with no gaps. I now have 1150 watts of flexible panels on my roof.

 

[Tomthumb62]

I don't recommend this install.

I Did this very same install on a rubber roof. After a couple of months, the tape started to peel the rubber off the roof, making a sort of bubbling. Wind must get under those and vibrate them.

Now, when I install these flexible panels, I tape all four sides completely down with no gaps. I now have 1150 watts of flexible panels on my roof.

Good to know. We’re going to use a similar install but will screw down the metal rails. Currently they’re screwed down with a fender washer and lock washer at each grommet point. And a strip of gorilla tape at the front. Wind vibrations have loosened two of the rear screws, and the washers have gone A wall as a result. All the other screws were tight and unaffected. This happened after less than 2500 miles. And gorilla tape isn’t good for more than about 500 miles.

 

[JamesRich]

I don't recommend this install.

I Did this very same install on a rubber roof. After a couple of months, the tape started to peel the rubber off the roof, making a sort of bubbling. Wind must get under those and vibrate them.

Now, when I install these flexible panels, I tape all four sides completely down with no gaps. I now have 1150 watts of flexible panels on my roof.

My camper has a pvc roof which is stiffer than the rubber roofs. I've seen campers rolling down the highway with the roof puffed up! Not good! I also have the advantage over a RV since my camper is a fifth wheel that is higher in the front, then slopes down to the back. If I mount the panels after the start of the slope they should get less wind.
James

 

[JamesRich]

Ok guys I did a test over the weekend. Made sure my batteries were fully charged & ran the main A/C until the batteries were too low & the inverter shut off. I got 4 hours of run time so even if the panels I add keep the batteries hot all day I won’t make it through a hot night with the 4 batteries I have. Got me thinking about higher voltage. Would a 24 volt system run longer with the same amount of batteries? I looked up budget inverters, is a gaindel inverter decent? I may pick one up & reconfiguring my batteries & run the test again.

 

[chrisski]

Would a 24 volt system run longer with the same amount of batteries?

No. the batteries has the same watt hours No matter if set up in series or parallel. Need more batteries to get more power.

What is the watt hour requirement For this overnight run?

 

[JamesRich]

Not sure just want to make sure I’ve got enough power for an 8 hour night. If I need more batteries I’ll buy more.

 

[Tomthumb62]

Not sure just want to make sure I’ve got enough power for an 8 hour night. If I need more batteries I’ll buy more.

If you can add more insulation to your RV, that can go a long ways to reducing your energy needs. But it’s usually not exactly an easy fix without heavy remodeling.

If you add more batteries, you want to add more panels and more/larger MPPT since you’ll need more charging power.

 

[Zwy]

Not sure just want to make sure I’ve got enough power for an 8 hour night. If I need more batteries I’ll buy more.

Install an inverter heat pump and throw the RV ac away or sell it. I'm in the process of finishing heat pump installation.

 

[JamesRich]

Install an inverter heat pump and throw the RV ac away or sell it. I'm in the process of finishing heat pump installation.

A friend at work keeps after me to swap to 12 volt A/Cs, claims they are a lot more efficient. I'm sure they are but right now I'd rather buy more batteries! If my current units crap out I'll get a 12 volt unit like I did with the refrigerator. I just looked them up, a 12k 12 volt unit is $2400! Says it draws from 22 to 55 amps which seems like a lot. I'll have to check amp draw from the inverter with my unit running.

 

[chrisski]

A friend at work keeps after me to swap to 12 volt A/Cs, claims they are a lot more efficient.

Does your friend have one? Also, what size is his camper? Also yours?

I have a fifth wheel and a 12 volt AC would be impractical for 250 square feet. I’d need a 15k btu AC which if I could find an 12 volt inverter AC would probably pull 120 amps.

 

[Zwy]

A friend at work keeps after me to swap to 12 volt A/Cs, claims they are a lot more efficient. I'm sure they are but right now I'd rather buy more batteries! If my current units crap out I'll get a 12 volt unit like I did with the refrigerator. I just looked them up, a 12k 12 volt unit is $2400! Says it draws from 22 to 55 amps which seems like a lot. I'll have to check amp draw from the inverter with my unit running.

Forget the 12V AC unit. The COP and SEER ratings are not very high compared to an inverter mini split. 48V DC might get you some decent COP and SEER ratings.

The last 2 years we have had discussions about the DC powered HVAC units for RV's and trucks. I have yet to see any decent COP and SEER ratings, if they even publish the ratings as RV units are exempt from ratings. One can use a calculator to determine COP and SEER if you have the actual data.

 

[Tomthumb62]

A friend at work keeps after me to swap to 12 volt A/Cs, claims they are a lot more efficient. I'm sure they are but right now I'd rather buy more batteries! If my current units crap out I'll get a 12 volt unit like I did with the refrigerator. I just looked them up, a 12k 12 volt unit is $2400! Says it draws from 22 to 55 amps which seems like a lot. I'll have to check amp draw from the inverter with my unit running.

12v appliances are at worst, only 9% more efficient than 120v ones. But they’re WAY more expensive, as you know.

An efficient 120v heat pump can be had for like $600, installed in an afternoon (even diy via YouTube) and you only need professional help to hook up the coolant lines and energize the system. There are some good YouTube videos of van lifers who have done this exact thing. If someone can make it work for a van, then any other kind of camper can make it work.