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Converting a Vintage Camper to Solar Power 101

Many thanks to Adam Wiedmann for this information.

In a recent restoration of my '68 Serro Scotty camper I converted all my electrical to solar. Originally the Scotty had a combination of 110v AC "shore" power, a few 12v DC lights that ran off the tow vehicles harness or some added an onboard battery. There also was a propane gas light. I wasn't satisfied by this. I wanted all my power all the time where ever I was. I camp primarily in remote areas hunting and fishing where plugging in is not an option. So, I did my research and converted everything to 12v DC sourced by a single solar panel. My refrigerator runs on propane. My entire camper is unplugged and untethered now. The system is always on and there is no setup needed upon arriving at camp.

There are a few key things to know up front if this is something you are considering; you cannot run big items such as a refrigerator or microwave. Well you can but not for long. If you like always running a fan the electric consumption will need a large system and can get costly fast. But, if you want to run all of your lighting, water pump, occasional fan and small accessories solar is a great option.

There are three basic items that make a solar system; the solar panel to create power, the battery to store it and a charge controller to ensure the battery is protected from over charging and over draining. The controller will cut in/off in the 11-14v range depending on the unit. Most charge controllers also have fuses to protect everything from electrical shorts.

I converted all my lighting to LED bulbs. This drastically reduced my consumption for lighting by almost 90%. There are a multitude of 12v LED bulbs on the market with many different standard automotive bases. For example I used a dome light from Vintage Trailer Supply that was originally equipped with (2) 20w halogen bulbs. I found LED bulbs to replace them that had a warm incandescent light and reduced consumption from 40w to under 4w with no change in function.

I also converted all 110v AC fixtures to 12V DC. I found my base sockets for this at the auto supply store. I removed the old socket and rigged In the new 12v ones. I wasn't too concerned with the energy loss due to resistance, so I actually used the original 110v wires for many of my fixtures. I even ran a new wire and turned my gas Humphrey into an electric LED light, which is great.

This is a good time to point out this equation for figuring out consumption and production. Some things are rated in amps and others in watts. I preferred to use watts to rate everything. I used 12v as my converting number, as it is a likely average voltage for the system to run at.

amps = watts/voltage

So, once you've figured out what you would like to power, its time to work up an estimate on consumption over a 24hr period. It's as simple as looking at the ratings for all bulbs,fans, pumps and other devices and adding them up and multiplying them by hours of use. I ran my estimate for worst case scenario. I've been known to camp well into December, so at times I'd want all my lights up to 5 hours a day. With all my lights, 30 min of water pump and a 20% buffer, I figured my max consumption would be 100w in a 24hr period, at most. If you plan on using an inverter for 110v AC don't forget to factor in loss in the inverting process plus the consumption of the appliance etc. I stuck to all 12v.

Now you know your target for production from a solar panel. I can't say there was anything scientific about how I estimated how many watts I'd produce daily. I did however estimate again for worst case scenario. I estimated full charging hours I would get on an overcast day in northern Maine in December. By full charging hour I mean what would be an ideal full sun hour for maximum efficiency for charging. I used number of daylight hours and starting reducing due the factors above. I figured I'd get 30%-40% of the light that would be considered ideal. Worst case I figured I'd get 3.5 full charging hours in that scenario. I divided my consumption by full charging hours to figure out what size panel I'd need (100w/3.5 hours = 28.6w). I bought a 30w panel.

If I only camped during the summer I'd get more full hours of charging and need a smaller panel. Also, I could add another battery down the road and be able to run a vent fan during the summer due to more charging hours/production.

Next is storage. You'll need a battery capable of usable storage equal to your consumption. This amount isn't always clear with some battery companies. I say usable storage because the amps under 11.25v, or so, cannot be used, and should not be used. The charge controller will shut off power under 11.25v (depends on controller some are at 11 others at 11.5) to prevent battery damage from too much discharge. So, many batteries might be rated for X amp hours but only part of that amount will be usable as they might be rating the battery to dead (0v) rather than 11.25v. Generally usable amps are 40-45% of the batteries total amp hour rating. For example a 100ah battery will likely have 40-45 useable amps. This number reduces with battery life and cold temperatures (as low as 20% of the original total ah rating).

I used a large deep cycle marine battery from a boat that I happened to have. I lucked out and it works fine for my needs. I wasn't able to easily find the rating I was looking for so I just tested it in the camper by leaving the lights on overnight which was more than I figured it could do or I'd ever need. Batteries specifically made for solar systems are much more likely to give you the information needed. Deep cycle batteries will have a longer service life than a standard car battery. Golf cart batteries are another good option. Typically gel batteries have a larger amount of usable amps in them than lead acid and are safer because they are sealed. Do not forget that you will be sleeping with your batteries and they can release gases and go boom if not taken care of well. Overall I recommend deep cycle marine batteries. They are great for the job and are designed to take the pounding of a boat. Always use a plastic battery box to house your battery.

None of my numbers were exact and my estimates were always done on the conservative side. If you go bigger than you think you'll need, the odds are when you finally test it all out you will not be disappointed, or sitting in the dark. But, testing it out will be the only way to know for sure. I haven't camped in a shady site during a week of overcast skies yet, for example.

A common and tempting misconception is that during the day one has more power available to use because they are making power from the panel. This is only true once the battery is fully charged. Otherwise the power being made is going towards charging. Consumption over a 24hr period has to equal production. Think of the panel as a trickling water faucet, the battery as a bucket and your consumption is the amount of water you use daily from the bucket. There's no gain in volume by using the water directly from the faucet until the bucket is full.

I mounted my panel flat on the roof. These newer panels don't need to be aimed at sun like the ones of old. They don't need to even be in direct sunlight. Their efficiency is pretty good in many scenarios. I've found mine actually charges well into dusk and even with a good moon. It's not much charge but its impressive it gets any at all. I put my battery in my closet, the panel is located above it. It really doesn't matter where you put these items because you can run longer wires to accommodate.

I have considered running a hot feed wire off my 7 pin as a backup for charging, but haven't needed it. I once had a charge lead fall off the battery (alligator clip) while on a trip. I removed the battery and used jumper cables to charge the battery off of my truck while it was running. I got rid of the alligator clips to solve the issue but am satisfied with the jumper cable backup if something else failed. I did add a small LED voltmeter display to be able to monitor the battery's level to avoid any future nonsense or know when to conserve if ever needed.

Bottom line for most people a 25-30w system with one larger 70-100ah battery will work fine. A 50-100w system with 2 batteries will take care of those that like their electric conveniences. It's pretty great to be able to pull up anywhere and have all the power you need w/o worrying about plugs, cords or any setup, be it; rest area, a friends house or camp site.



None of my numbers were exact and my estimates were always done on the conservative side. If you go bigger than you think you'll need, the odds are when you finally test it all out you will not be disappointed, or sitting in the dark. But, testing it out will be the only way to know for sure. I haven't camped in a shady site during a week of overcast skies yet, for example.

A common and tempting misconception is that during the day one can run all the power they want because they are making power from the panel. This is only true once the battery is fully charged. Otherwise the power being made is going towards charging. Consumption over a 24hr period has to equal production. Think of the panel as a trickling water faucet, the battery as a bucket and your consumption is the amount of water you use daily from the bucket. There's no gain in volume by using the water directly from the faucet until the bucket is full.

I mounted my panel flat on the roof. These newer panels don't need to be aimed at sun like the ones of old. They don't need to even be in direct sunlight. Their efficiency is pretty good in many scenarios. I've found mine actually charges well into dusk and even with a good moon. It's not much charge but its impressive it gets any at all. I put my battery in my closet, the panel is located above it. It really doesn't matter where you put these items because you can run longer wires to accommodate. 



I have considered running a hot feed wire off my 7 pin as a backup for charging, but haven't needed it. I once had a charge lead fall off the battery (alligator clip) while on a trip. I removed the battery and used jumper cables to charge the battery off of my truck while it was running. I got rid of the alligator clips to solve the issue but am satisfied with the jumper cable backup if something else failed. I did add a small LED voltmeter display to be able to monitor the battery's level to avoid any future nonsense or know when to conserve if ever needed.

Bottom line for most people a 25-30w system with one larger battery will work fine. A 50-100w system with 2 batteries will take care of those that like their electric conveniences. It's pretty great to be  able to pull up anywhere and have all the power you need w/o worrying about plugs and cords, be it rest area, a friends house or camp site.

Adding a photo controlled switch (thanks Adam)

I recently installed a photo controlled switch so my camper lights go on and off, dusk to dawn. My camper runs on solar and I put the sensor/switch in the closet with my battery. The light from the small window there is enough to actuate it. I put in an override so I ca use power during the day if I like. It is nice to look out the window at night and see my Scotty all lit up, and is a security bonus to have the lights come on while camping even if I am not there. I set up the switch to control all of the power leaving my charge controller so anything I have left turned on will come on at dusk, which right now is the porch light and one interior light. $10 and 30 minutes to install.

 

National Serro Scotty Organization | Delton, Michigan 49046