It is good to know if there is still enough power left in the battery after watching TV and having had a few lights burning all night. You are not plugged in and you donít want to kill the battery. A digital 12 Voltmeter could tell you exactly the state of your battery and when it's time to start up your generator or towing vehicle to charge your battery. The how to install a digital 12 Voltmeter is explained in the link below.
Marlene and Benno's Odysseys on Land and Water: How much juice is in your 12 Volt Battery?