Marcia and I recently vacationed on Cape Cod in Zack, a 2015 Advanced RV Ocean One. (Read Marcia’s blog about the trip.) While boondocking for seven days in hot weather, we ran tests to monitor battery voltage and coach and refrigerator temperatures.

For the majority of the trip, we had the camper closed-up and parked in a small town on Buzzard’s Bay, in partial sun. (We were sleeping in a house nearby.) Zack is equipped with solar panels and 400 amp hours of lithium batteries, but does not have Advanced RV’s latest battery cells, or battery and solar control and monitoring system. We did not plug in the entire trip; autocharge never kicked in. We used lights and MaxxFan and charged our computers, but we didn’t need air conditioning. The refrigerator was on, and at least partially full, the whole trip. When Zack was parked, we only opened the refrigerator door once or twice per day. Also, when parked, we installed insulating window covers on the cabin windshield and side driver and passenger windows.

Over the course of the trip, we were able to keep the motor home interior reasonably close to ambient temperature (within 7 degrees). For example, on the hottest day, at 5:30 p.m., the outside temperature was 92 degrees F. and inside temperature was 99 degrees.

As you’d expect, refrigerator and freezer temperatures followed temperatures inside the motor home, rising during the day and dropping at night. At the hottest reading, the refrigerator temperature was 48 degrees, and the freezer was 24 degrees. The average temperature in the refrigerator was 44.4 degrees; in the freezer, it was 14.4 degrees. FDA notes that bacteria can grow when food temperatures rise above 40 degrees for two hours. So we might have hit a danger zone, but hopefully it lasted for less than two hours.

As for battery usage, the solar panels kept the batteries in the coach between 13.1 and 14.2 V for the whole trip. Most days, the coach battery voltage was 13.3 V. The autogen, when enabled, comes on at 11.8 V. We were fortunate to not need AC, which would have put further demands on the batteries.

The trip taught us several important lessons about hot-weather boondocking in a Class B:

Remember the basic principles of refrigeration and air conditioning. The performance of both systems depends on outside temperatures, radiation from the sun, motor home and refrigerator insulation (from both radiated and conducted heat), and the number of times and how long doors are open.

Install reflective, insulating covers on the windshield and driver and passenger door windows whenever you’re stopped for more than a half hour in hot weather. If stopped longer, close all window curtains and install covers on the rest of the windows (if you have them). When uncovered, the windows act like a greenhouse, heating the inside of the coach well above outside temperatures.

Crack open a few vent windows and turn on the MaxxFan to draw in outside air and exhaust the hot, interior ceiling air. Like in a greenhouse, the air inside a motor home should circulate.

If you’re leaving pets or people in the coach, immediately install window covers and turn on the AC whenever you stop. If you’re on battery power, set the AC at a comfortable temperature before you leave, about 78 degrees. Don’t set the temperature much lower and leave. If you set the temperature lower than the system can achieve in a short time with the doors and windows closed, the AC won’t cycle. You’ll use much more battery than if you had set the AC to a higher temperature where the the system could cycle on and off as required to maintain the temperature.

Shut the doors, already! Minimize the amount of time the coach and refrijgerator doors are open. The less they’re open, the cooler it will stay in the motor home, and the less battery it will take to keep the coach and refrigerator cool.

When sleeping, open the windows on each side of the bed and turn on the MaxxFan. This setup is often more pleasant—and always quieter and more energy efficient—than using AC. The MaxxFan has a variable speed motor, so you can set the fan speed low enough to limit noise while still creating a breeze. We’ve found this arrangement makes for comfortable sleeping in outside temperatures up to 85 degrees.

Do you have experience overnighting in hot weather? We’d love to hear your feedback and tips, as we’re constantly looking to maximize the effectiveness of our cooling and refrigeration systems.

You can learn more about Advanced RV’s innovative systems here.

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