
After installing a 12 volt outlet inside my camper, I use a battery monitor that plugs into the cigarette lighter style power receptacle. This allows me to conveniently monitor available battery charge without crawling under the slide-out bunk, opening the battery box, and checking the battery directly with a multimeter.
Voltage | Charge |
---|---|
12.6+ | 100% |
12.5 | 90% |
12.42 | 80% |
12.32 | 70% |
12.20 | 60% |
12.06 | 50% |
11.9 | 40% |
11.75 | 30% |
11.58 | 20% |
11.31 | 10% |
10.5 | 0% |
The chart above shows how much charge you have left for a given voltage reading. That’s right – a 12 volt battery is actually dead at 10.5 volts and fully charged at 12.6+ volts. And to prolong battery life, you don’t want to go below 50%.
You’ll want to take readings after the battery has had a chance to sit dormant for a while. Measurements taken while a device is drawing from the battery can be wildly inaccurate. For me, this means measuring after having been out of the camper all afternoon on a hike.
Extra Credit
Some RV owners will use more elaborate solutions like the Tri-Metric, monitoring not just battery percentage but also charging and discharging amps. This device truly is amazing and I encourage you to also check it out to determine what is best for your use.
Personally, I get by just fine with the simpler and cheaper cigarette lighter electric meter option. I simply plug it in to check the voltage and then unplug to a

Scott
I've been camping regularly since I was a kid, from quick Cub/Boy Scout trips to week-long backpacking trips and everything else in-between. We got a popup camper when our kids were 1 and 3 years old to enjoy more time outdoors together alongside a few conveniences like heat and running water. Since then, we've spent over 75 nights together as a family in our popup camper. I've learned a lot about the intricacies of a popup tent camper during this time and love to share those lessons here for the benefit of others.
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