Water heater battery drain

[Bohemian]

I once had a total battery drain during 10 days of spring time storage. Only thing I failed to turn off was the water heater. Lost the fridge contents.

I figured it only drew power to light the flame, a few times a day. Not thinking that way now.

I checked voltage with a 100'ths reading meter, stable no use overnight. Then I flicked on the water heater. Dropped about a 10th. Stayed low while it heated. Hmm. That's not just sparking the flame.

When does the LP water heater use how much DC power?

[Splitrock]

Which water heater?

[bryanl]

Lost fridge contents?

Start with that appliance. It runs at about 10 watts (~0.9A at 12v) or 240 watt hours per day. For a week that'd add up to almost 1.7 kWh. A 2 battery bank of 120 pounds has about 1.4 kWh as a 'most you'd want to use' target. Toss in Peukert and a discharge to bring the voltage down to 11.5 to kill the fridge and you'd maybe get up to 3 kWh available. That means the fridge alone is enough to give your batteries a hard time on a ten day stretch.

The water heater control board might use an equivalent amount and the various alarms would also use another 10 watts or so. It all adds up.

[idroba]

My DSI water heater takes about 1.2 amps when lighting and .7 amps while the burner is on. The gas valve is electric and the control system takes power. There is more draw than just the circuit to light the burner. Mine takes nothing when the burner is not in operation.

[Bohemian]

Originally Posted by Splitrock

Which water heater?

It's an Atwood 6A-8E, 6 gal.

[Splitrock]

Wouldn't it be easy to switch the power supply to the water heater? I'd be wondering if maybe the refrigerator would be more of a 12 volt draw if left running on gas. My trailer is still in construction mode. My storage spot has a 30 amp 120 volt outlet for my future enjoyment.

Good luck with your maintenance and travels.