Battery capacity

Odsox

I'm hoping that someone with a few more brain cells than me can answer this.
If I have a 110Ah battery bank supplying 48v to a 95% efficient inverter, how long would it supply 220v at 500 watts per day ?
Assuming a limit of 50% discharge on the batteries of course.

Cheeble

Very roughly:

500 watts at 95% efficient means approx 11A at 48 volts, so your battery will reach 50% capacity after 5 hours.

If it's critical, I'd suggest a more detailed look.

Cheeble-eers

Odsox

Thank you.
That's refreshing as that's what I worked it out to.

The only difference is that I want to draw 500 watts TOTAL in a 24 hour day, so can I assume that would then be roughly 5 days supply ?

Cheeble

Glad we agree on the calculation

Watts are a measure of the rate of energy use (much like Km/h are a measure of the speed of a car), so it's not quite correct to talk about watts total in 24 hours (the equivalent would be that I want to drive a total of 60km/h in a day).

If you want to use 500W over 24 hours, then that would be a total of 12,000 Watt-hours or, more conventionally 12kWh (kilowatt-hours), but your battery would go flat half way through the day.

On the other hand, if you want to use 500 watt-hours over a 24 hour period, then that would be a rate of just under 21 Watts, and your battery would last nearly ten days.

If this doesn't help, tell us a little bit more about what you're trying to do, and I'll try to shed some more light on it.

Cheeble-eers

Odsox

Cheeble wrote: »

Glad we agree on the calculation
On the other hand, if you want to use 500 watt-hours over a 24 hour period, then that would be a rate of just under 21 Watts, and your battery would last nearly ten days.
Cheeble-eers

Nope, you lost me on this one

OK, what I'm doing is this.
I have 4 x 12v batteries @ 110 Ah feeding a 48v inverter and I want to know how long I can run my house lights before recharging (windless days on a turbine)
I have estimated how long individual lights would be on, so I have say one 20 watt bulb on for 4 hours a day, another 9 watt for 6 hours and so on.
The totals in watt hours is 414 which I was rounding up to 500 watt/hours

The way I worked it out (almost certainly wrongly) is the battery bank contains 110 x 48 = 5280 watt/hrs and therefore should run the lights for 10.56 days or 5 days to the 50% limit.

Cheeble

Hi, your method, and the calculation look ok to me.

I was only asking the question about watts and watt-hours for clarity.

Cheeble-eers