# How long lifepo4 battery power a tv

#### mrel

Joined Jan 20, 2009
185
Have lifepo4 battery 100 ampere hour, 12 volts.
Questions
(1)Using power inverter 400 watts ,not pure sine wave inverter, connect inverter to battery plus and minus terminal.
(2) Television draw 120 volts ac using 25.75 watts, how long can use battery and the inverter before battery drain out?

#### Ya’akov

Joined Jan 27, 2019
8,973

#### Dodgydave

Joined Jun 22, 2012
11,236
Rough guess assuming the inverter is 90% efficient, would draw about 3amp from the battery, so that would be 30hrs..max!..

#### MisterBill2

Joined Jan 23, 2018
17,787
My cheap 400 watt inverter draws 10amps at 100 watts out with a 12.00 volt supply. But the current goes up rapidly as the input voltage drops. So the efficiency is less than 90%, closer to 85%. A 100 amp hour 12 volt battery thus holds 1200 watthours of power. At 100% efficiency that would be 1200WH/25.7W hours, but you may only get about 85% of that.
Unfortunately I did not measure the no load current draw of my cheap inverter.

#### crutschow

Joined Mar 14, 2008
34,028
But the current goes up rapidly as the input voltage drops
Did it go up proportionally more rapidly than the voltage dropped?

#### MisterBill2

Joined Jan 23, 2018
17,787
Did it go up proportionally more rapidly than the voltage dropped?
No, the output did not drop, but the current went from 10 amps to a bit over 11 amps as the supply dropped about half a volt. It might hsve been a constant power in=power out sort of relationship. I did not take it very far.

#### mrel

Joined Jan 20, 2009
185
Have lifepo4 battery 100 ampere hour, 12 volts.
(1)Using power inverter 400 watts ,not pure sine wave inverter, connect inverter to battery plus and minus terminal.
(2) Television draw 120 volts ac using 25.75 watts, how long can use battery and the inverter before battery drain out?
I am one that post this questions ,I did test ,using setup as i posted the battery power television for 32 Hours before Bms turn the television off.
mrel

#### Dodgydave

Joined Jun 22, 2012
11,236
Have lifepo4 battery 100 ampere hour, 12 volts.
(1)Using power inverter 400 watts ,not pure sine wave inverter, connect inverter to battery plus and minus terminal.
(2) Television draw 120 volts ac using 25.75 watts, how long can use battery and the inverter before battery drain out?
I am one that post this questions ,I did test ,using setup as i posted the battery power television for 32 Hours before Bms turn the television off.
mrel
So i wasn't too far off with my guess.

#### MisterBill2

Joined Jan 23, 2018
17,787
OK, drawing from a storage battery at a lower rate does allow more energy to be recovered. And the TS inverter may be more efficient than my cheap inverter. It would be useful to know the brand and model of the inverter that the TS was using.. My cheap inverter is a "cobra" brand, model CPI 480. \$5 at a yard sale, complete with no promise that it would work. But with a home-made lighter plug cord, about #18 wire, I could guess that the rest of the setup never had a chance to work.