Cigarette Lighter Temp/Current/Voltage Meter

Just be aware of what you're measuring. The voltage is the voltage at the charging port, which under heavy loads may be a little different from the battery voltage (depending on the details of the wiring of the RV), but should be more accurate than the four-LED bargraph display the RV probably came with. The current it's measuring is just the current used by the device plugged in and being charged—it's not in any way your overall battery current. The temperature, as you say, is just the temperature of the charger, and probably not even all that accurate for ambient temperatures since the charger warms up itself.

If you want a USB charger and a simple voltage monitor, it would probably be okay. Beyond that, I'd look at other units.

Hi,

There are some that read to xx.xx which may be better to know.