Electric AmpHour Question

[ScottishGasMan]

Hey all

I know its not domestic electics but thought this would be the best place to ask.

Ive got a battery, with an inverter for a car, like a power pack. It can supply 300w max 240v AC, and its a 20ah battery.

is there any way of working out how long this will run for on full charge. like if i say i use it to power a 100wbulb or 300 watt TV, how long before it runs out?

cheers guys
SGM

 

[Adam_151]

A 20ah battery means it can supply 20A for one hour, or 1A for 20 hours, etc (well almost, it'll be rated at a certain current draw and for others the figures might not quite add up... but roughly it works)


Your 300w inverter running at max will mean you have 300/240 = 1.25A of available current on the LV output side, and will draw 300/12=25A on the ELV input side, its the wattage that stays the same on both sides (actually thats not totally true, its not 100% efficent, it'll need more than 300w in to 300w out!)

Your 100w lamp.... the ELV input side of inverter will be drawing say (100*1.2)/12 = 10A, so your 20Ah battery will last 2 hours. (the 1.2 is a figure I pulled out the air to represent the inverter is not 100% effcient)