Boondocking with Air Conditioning
The goal for this build was full electrical power for all appliances, especially air conditioning, with no electrical hookups and the ability to run air conditioning, as needed, even with two days in a row of cloudy weather. As is often the case, the amount of available space on the roof constrains the amount of solar charging capacity and inefficient appliances lead to quick battery drain during periods of no sun. How did we solve this problem?
First, we needed to remedy the two largest consumers of electrical energy for this camper – the refrigerator and air conditioner. Typical 15k BTU roof-top air conditioners consume around 1,400 to 1,600 watts of power when running. That’s easily 20kWh of energy per day on hot days. A typical 6 cubic foot absorption refrigerator running on 120 volts AC consumes about 450 watts when running, or about 5kWh of energy per day. That’s 25kWh of energy per day just to stay cool. And to achieve the goal of running everything for two sunless days would mean at least 50kWh of battery capacity, which is not practical.
We replaced the existing fridge with a new 11 cu foot 12 volt DC compressor fridge that uses about 65 watts of power, or 85% less energy consumption. We installed a 12k BTU mini-split air conditioner that uses on average about 400 watts on the hottest days. Combined, the new air conditioner and fridge consume up to 10kWh of energy per day, or less than half required before.
Running existing air conditioning only occasionally is what most clients request or they use a generator when they need air conditioning. In this case, the owner did not want to use a generator to provide power for weekend trips.
Sizing the system
Another constraint was the space available inside the camper for the batteries and equipment. The owner wanted to preserve outside storage for outside items so the decision was made to install everything under the master bed. It was a tight squeeze, but we installed 15kWh of battery capacity, 1,600 watts of roof-top solar, and 3kVA of Victron Energy power generation equipment into the storage compartment. The client opted to keep the roof-top air conditioner in place for now. This provided the client with 1.5 days of sunless run time (only using battery power) in the hottest months with air conditioning. Removing the roof-top air conditioner will provide another 400 watts of solar power on the roof to charge the batteries even quicker. The combined 2,000 watts of roof-top solar will generate a small amount of power on cloudy days, and get the customer closer to their two cloudy day goal. An additional 300 watts of ground-mount solar panels that can be used as solar awnings over windows or propped on the ground round out this charging system. For extended trips, this client brings a 2,000 watt Honda generator – converted to run off the RV propane tanks – to charge the batteries if there are more than two cloudy days in peak Summer temperatures.