Having just completed my camper van conversion I ran an interesting test today heating hot water off of battery power. Battery is a nearly new 8D East Penn Deka AGM about 230 amp hours, inverter is a Xantrex sine wave 1000, water heater is an Isotemp 4 gallon with a 750 watt element. Battery is monitored by inverter which shows voltage and current, and I have a separate voltmeter on my DC switch panel. There was no battery charger running during test. Additional non-inverter load on the battery was a couple of amps for two Maxxair fans at half speed and 8 LED lights.
I had just filled water tank and heater and I guess the water temperature was about 70 degrees F. coming from the underground pipe. Very quickly after start the battery voltage dropped from full charge 12.8 to 11.9 and the DC current jumped around 79 to 81 amps all during the test. After 30 minutes the water was very hot and usable for any hot water purpose. After 42 minutes the heater thermostat was satisfied and shut off. Water was very, very hot at least 120 degrees F.
The battery instantly recovered to 12.3 and within 10 minutes recovered to 12.5. this seems about right as some 50 plus amp hours had been taken from the battery.
I had just filled water tank and heater and I guess the water temperature was about 70 degrees F. coming from the underground pipe. Very quickly after start the battery voltage dropped from full charge 12.8 to 11.9 and the DC current jumped around 79 to 81 amps all during the test. After 30 minutes the water was very hot and usable for any hot water purpose. After 42 minutes the heater thermostat was satisfied and shut off. Water was very, very hot at least 120 degrees F.
The battery instantly recovered to 12.3 and within 10 minutes recovered to 12.5. this seems about right as some 50 plus amp hours had been taken from the battery.