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How low should I allow the battery go on an inverter &/or before running the generator


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I have just purchased a Fleetwood Bounder and and learning how to manage power. During the walk through when I picked the Bounder up at the dealership both the engine and house batteries registered at 16.6 volts. Tech told me that a battery was effectively dead at 12.00 volts. Can someone tell me a threshold battery voltage reading upon which I need to turn off the inverter and/or run the generator in order to avoid draining the batteries?


Thanks from a newbie.


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Nope, there is no specific voltage where the inverter needs to turn off, it is more complicated than that. Voltage from a battery depends on both the state of charge and the current being drawn so a voltage that would be fine under a heavy draw would be dangerously low under only a light load. A common inverter automatic shutdown voltage is 10.5 volts, that voltage from a resting battery means it is likely damaged, from a battery supplying 50 amps of current it is probably safely above danger. However if you are just running a small TV it is likely in or near the danger zone.


If you are cheap, you can make yourself a cheat sheet by using a resting battery voltage chart and comparing your battery under load and then after a rest to it.


Make sure your battery is fully charged, over 12.7 volts.

Run your inverter under your normal load for an hour.

Check the battery voltage with your load present and chart it.

Remove as much of the battery load as possible and wait 30 minutes.

Check the resting battery voltage and put it on your hand made chart along with the matching percentage from the chart below.


The chart(s) you make will be very different if you are watching TV or microwaving something due to the different battery currents.






An alternative is to go out and check the specific gravity with a good calibrated float hydrometer with temperature correction but that is a pain.


Second option is a good battery capacity meter that reads in amps used and percentages, it is more expensive than hydrometer but far less work while being far more accurate than the voltage estimates. I'd vote for this option!

First rule of computer consulting:

Sell a customer a Linux computer and you'll eat for a day.

Sell a customer a Windows computer and you'll eat for a lifetime.

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