Acumulative power for an electromangetic induction generator

[tkellylord]

Hi all,

i'm test rigging a generator I am designing. Based on theories of electromagnetic induction and harvests small amounts of energy over a long period to hopefully charge your phone (fingers crossed).

I've worked out that I gain approximatley 22mA every second with an average voltage of 1.5v. The device will charge for approx 6 hours.

I wanted to find roughly how much i could charge my phone. I've tried to work it out but not 100% this is write. If you have a second could you please check over this...



coulombs = amps X time(seconds)

And 1 ampere hour = 3600 coulombs

A phone battery that is 1400 mAh or 1.4A/h equates to 5040 coulombs. so in total it needs 5040 coulombs of electricty passing into the battery in order to charge it. That means for a 6 hour charge we need to have 5040 coulombs of electricity delivered in a 6 hour period, therefore we need 5040coulombs/the number of seconds in 6 hours

5040/(6 x 60 x 60) = 0.233 amps second.

so if the average current was to be 22mA or 0.022A then we could accumulate 0.022 x 6 x 60 x 60 coulombs = 475.2. Using the 1400mAh phone battery as a reference the the phone could operate at this capacity for 5.657 minutes.( 5040/60 = 84 coulombs/minute).

If the phone uses 5Watts of power at 3.7 volts, that gives 1.35 amps.................5.86 minutes of full use. ((3600 x 1.35)/60) = 81 and 475.2/81 = 5.86 minutes


thanks if you could check

Tom

 

[Resqueline]

Coloumbs & Ampere hours (or seconds) are not the correct units to use here. Joules and Watt hours are (they're the same btw.).

22mA * 1.5V = 33mW
1.4Ah * 3.6V = 5.04Wh
Time to charge: 5.04Wh / 33mW = 153 hours = 6.36 days (& nights)

Your estimation of the phone consumption seem a bit high. A 1.4Ah phone battery is pretty big, and most phones can usually be used to talk for hours with this capacity.

 

[barathbushan]

how are coloumbs and joules the same ?
am confused , please explain

 

[Resqueline]

Sorry my meaning got ambigous. I meant (3600) Joules = (1) Watt hours. Joules = Watt seconds. Never mind the Coloumbs.

 

[tkellylord]

Coloumbs & Ampere hours (or seconds) are not the correct units to use here. Joules and Watt hours are (they're the same btw.).

22mA * 1.5V = 33mW
1.4Ah * 3.6V = 5.04Wh
Time to charge: 5.04Wh / 33mW = 153 hours = 6.36 days (& nights)

Your estimation of the phone consumption seem a bit high. A 1.4Ah phone battery is pretty big, and most phones can usually be used to talk for hours with this capacity.

Yeah your right about the phone battery. Majority I found were around 0.9Ah. If we use that...

0.9Ah * 3.7V = 3.33Wh
time to charge = 3.33Wh / 0.033W = 101 hours

as it charges for 6 hours a day...

(6 / 101) * 100 = 5.9%

So one day of charging (6 hours) would charge the phone 6.9%

not a bad start. Although this doesn't take into consideration losses along the way.

Thanks for your help!