Guest Posted September 2, 2009 Share Posted September 2, 2009 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 Quote Link to comment Share on other sites More sharing options...
macey2kk Posted September 2, 2009 Share Posted September 2, 2009 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. Quote Link to comment Share on other sites More sharing options...
macey2kk Posted September 2, 2009 Share Posted September 2, 2009 also... if it is bulbs you are using... consider 12v bulbs.. or consider 240v low energy bulbs ie. the 10w flourescent type you get free from british gas! Quote Link to comment Share on other sites More sharing options...
Guest Posted September 2, 2009 Share Posted September 2, 2009 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 Quote Link to comment Share on other sites More sharing options...
Phil_P Posted September 2, 2009 Share Posted September 2, 2009 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 Quote Link to comment Share on other sites More sharing options...
Phil_P Posted September 2, 2009 Share Posted September 2, 2009 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. Quote Link to comment Share on other sites More sharing options...
Guest Posted September 3, 2009 Share Posted September 3, 2009 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 Quote Link to comment Share on other sites More sharing options...
togsie Posted September 3, 2009 Share Posted September 3, 2009 While on the subject of things electrical could someone tell me what a Dielectric is Regards. Togsie. Quote Link to comment Share on other sites More sharing options...
Phil_P Posted September 3, 2009 Share Posted September 3, 2009 (edited) 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) Edited September 3, 2009 by Guest Quote Link to comment Share on other sites More sharing options...
Phil_P Posted September 3, 2009 Share Posted September 3, 2009 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. Quote Link to comment Share on other sites More sharing options...
togsie Posted September 3, 2009 Share Posted September 3, 2009 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. Regards. Togsie. Quote Link to comment Share on other sites More sharing options...
alan_k Posted September 4, 2009 Share Posted September 4, 2009 Togsie go and hide under your stone. Made me laugh though Alan Quote Link to comment Share on other sites More sharing options...
Phil_P Posted September 4, 2009 Share Posted September 4, 2009 I'm not talking to him! Ever again! I refuse! No, no, 'sorry' won't wash this time! Quote Link to comment Share on other sites More sharing options...
alan_k Posted September 4, 2009 Share Posted September 4, 2009 It was a good answer of yours Phil. Alan Quote Link to comment Share on other sites More sharing options...
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