I’ve always like to compare camping to a video game. In a typical role playing video game your character is some unlikely hero without weapons, armor, or magic. Your hero gathers items and abilities throughout the course of the game. Most of us start our camping in a similar fashion. We have a sleeping bag and a tent. Over time we gather more sophisticated gear to make our adventures easier and much like the characters in a typical role playing video game we are quickly divided in to different character classes. Our major character classes in camping are the backpackers, car campers, small RV campers, and large RV campers.
No matter what type of camper you are a solar panel will be useful. The scale and sophistication of your solar setup will vary dramatically depending on whether you are an ultra light backpacker or an owner of a 40 foot RV.
We camp in a tent trailer. We are a class of camper, akin to pop up campers, belonging somewhere between those who tent camp outside their car and those who have hard sided RV’s who have a roof on which to mount a solar panel.
No matter what type of camper you are you should have a fundamental understanding of electricity to plan your solar setup. If you’re getting worried… don’t. I should have failed Electricity and Magnetism in school. This isn’t going to get very complicated. You only need to know two things for now:
First Thing: Watts = Volts x Amps
Second Thing: 1 Amp Hour will power a 1 Amp device for 1 hour.
Inverters to run AC (household electric) devices from a battery are very inefficient and if you are thinking of running air conditioners or even televisions from your DC power they may consume alot more power than you expect. Feel free to do the math to see how many Amp Hours at 12v would be consumed by your 110v walk in refrigerator but you should probably just save time and accept your new 12 Volt life.
Once you have accepted your new 12v life try to estimate the size of your electrical needs in amp hours from the devices you will run such as phones, lights, fans, water pumps, etc. Look up how many amp hours the battery in your phone holds. Expect to consume that from your RV battery every night when you recharge from empty. How many amps does each device use? Multiple that by your estimated usage hours. If all this is too much math and you’re better with your hands just put an ammeter between your battery and it’s connection to your RV to see how much is consumed when everything is turned on. That should give you a good estimate of consumption. For our family we have two phones, a couple lights, and a demand pump for water from our aquatainer jug.
Our estimate goes like this:
- two phones estimated at 6ah (3ah each per night)
- two lighting/fan devices at 5.2ah each per day (1.3a * 4 hours)
- water pump at 5ah (5a * 1 hour)
By this math we should need 16.2ah per day. The battery should be sized to run a couple days in case you can’t recharge due to cloudy weather or other circumstances depending how seriously off grid you are you might plan more. We won’t suffer much if we can’t charge our phones, use a flashlight, or need to do dishes in without a sink. We need about 35ah.
We chose a small and light 35 Amp Hour Relion Lithium battery because the capacity should meet our needs and we are towing with a small car. Weight is important to us.
The solar charging capacity for a day should be multiples of the battery capacity because solar panels are rated for ideal conditions that will never occur. If the batteries can’t charge for a day the panels should be able to recoup two days of capacity in one day. We selected a Renogy 100W solar suit case. If you’re paying attention, 100W at 12V is 8.3 amps. If we had 4 hours of perfect ideal conditions we might be able to put 33.2 amps in our 35 am hour battery. In reality those conditions never occur and even the solar charge controller that came with the suit case has energy losses. The best reading I saw during our first trip with this panel was 5.6A.
If we draw down 16.2 Amps each evening we can hope to fully recoup that in under three hours of bright sun each morning. After testing this it was really nice to see the solar charge controller read full during the mornings of our trip as expected..
Even with this small RV electrical with one battery, a solar charge controller, and a panel I was a little intimidated in designing it to size. I’m happy it seems to be working out. Let me know what you are planning and what you thought about this setup in the comments below.