RV Battery Dies Overnight? The Draw You Forgot

You went to bed with a full battery. You woke up cold, with the furnace off and the lights dim. On a fall night with no hookup, it happens to a lot of campers.

01The usual suspects

The furnace fan. A propane furnace still needs 12-volt power for its blower. On a cold night it can run a lot, and it's often the biggest drain.

Tank heaters. Several amps each when they're on. See RV tank heaters.

Always-on stuff ("parasitic draw"): - Propane/CO detector - Stereo and clocks - The fridge control board, even on propane - Water heater control board - USB chargers and anything plugged into an inverter - An inverter left on, even with nothing plugged in

Each is small. Together, over 12 hours, they add up.

An old battery. Lead-acid batteries lose capacity with age and can't hold a charge like they used to.

02How to find it

1. Turn everything off, then use a clamp meter or a battery monitor to see how many amps are still flowing.
2. Turn things on one at a time and watch the number climb.

A battery monitor (a shunt-based one) is the best tool here. It tells you exactly how much you're using and how much you have left.

03How to stretch it

• Charge it full before bed. Run the generator during allowed hours. See generator quiet hours.
• Turn the thermostat down at night and use a better sleeping bag.
• Turn off the inverter when you're not using it.
• Turn on tank heaters only when they're needed.
• Use a battery disconnect when the rig is parked.

04When it's time to upgrade

If you camp in the cold without hookups often, think about a bigger battery bank or lithium batteries (check their low-temperature charging limits), plus solar. See solar panel output on a short fall day.

A dead battery on a cold night means no furnace. Plan your power before the sun goes down.

Photo by Didgeman on Pixabay.

Related: Fall Camping: How to Stay Warm When Nights Drop Below 40