In general the carbon monoxide detector doesn't draw enough to matter. Many of them run on their own battery.
Possible problem areas include:
- Propane detector
- In some cases, smoke or carbon monoxide detectors but most of these have their own batteries
- Fridge ignition circuit
- Water heater ignition circuit
- Antenna amplifier
- Stereo (easy to leave on and forget about if inside a locker as is the case in my rig)
- Reading lights dimmed down but not shut off
- Lights inside storage compartments (again easy to forget unless there's a door switch)
- Tank level sensors if left on
- Furnace if thermostat is turned down but not off and it runs some of the time
Most rigs have a battery disconnect to deal with this.
"I dare you to say that to my face!" - David