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Watts and stuff!!!???!!!


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OK, I have a 130Ah battery, wired to a 100W 240v invertor

Lets say for the ease of my brain, that I have a 100w light bulb on.

How long will the battery last, and is there a simple way to calculate this. ??

SW :D

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saw this and thought it may help.....

it relates to different ah battery / bulbs,,,, but the logic and calcs are there..

happy calculating!

it really depends on the efficiency of your inverter.

eg if you presume the inverter is 75% efficient ..

85ah battery. 120watt lights.

v*a = w

250 * 0.5 = 125 so approx 1/2 amp

so approx 170 hours if you were to fully drain the battery and the inverter was 100% efficient - But if 75% then 120 hours .. ish.

Also you should only really drain the battery to 50% so half the time ..

so approx 60 hours.

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100 watts is roughly 1 amp

battery will use 10 amps for every 1 amp converted to AC

so a 130 amp battery will last with a 100 watt light bulb 13 hours, give or take a little depending on the reserve on ya battery .

something like that lol :P

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The watts being used on the light side will be approximately equal to the watts being supplied on the battery side, less a fairly hefty slice of inefficiency.

So, if you are using 100 Watts, you might need to supply 150 Watts

Watts = Volts x Amps, so Amps = Watts/Volts

Current demand therefore = 150/12

= 12.5 Amps (seems blinking high, have I done something wrong?)

Call it 13 Amps to make the sums easy

130 Amp/hour battery will supply 13 Amps for 10 hours (13 x 10)

My inefficiency factor might be a bit high, but the battery will probably drop below the voltage threshold to drive the inverter sooner rather than later, so I'd guess that it's about right on swings and roundabouts.

Phil

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saw this and thought it may help.....

it relates to different ah battery / bulbs,,,, but the logic and calcs are there..

happy calculating!

it really depends on the efficiency of your inverter.

eg if you presume the inverter is 75% efficient ..

85ah battery. 120watt lights.

v*a = w

250 * 0.5 = 125 so approx 1/2 amp

.

The error in this calculation is that 1/2 an amp at 250 volts, require 10ish Amps at 12 volts. Power consumption remains a constant (less any losses) not current drawn.

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yes this is how i figured it phil , inverters are ok if really needed but if you can avoid and use 12 volts is far more efficient

Where mains voltages will score though is when you are having to use long extension leads. The lower current of the 240 volts means less resistive loses in cables.

To run a long extension for 12 volts at 10 Amps would require hefty cable, and would still have appreciable loss.

This is why electricity is distributed around the country at up to 120 thousand volts.

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A dielectric is an insulator between two conductors. It is often used to describe the insulator used in capacitors, between the two charged plates, or the insulator in coaxial cable (antenna wire)

Phil, I feel slightly guilty now that you've taken the time to post such a comprehensive answer, BUT the correct answer is in fact... A Welsh electrician. Boom Boom. :lol:

Regards.

Togsie.

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