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Anonymous Poster

capacity calculation

11/03/2008 8:04 AM

how to calculate ampere hour of a 24 volt battery connected to a motor of input power 4 KW to run 2 hours?
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PWSlack
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#1

Re: capacity calculation

11/03/2008 8:22 AM

4kW times 2 hours, divide by a thousand is <tap, tap, tap>, er, so-many watt-hours, which is <tap, tap, tap>, that, then divide by 24 volts is, er, <tap, tap> so-many amp-hours. Eureka!

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rakesh_semwal
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#2

Re: capacity calculation

11/03/2008 9:35 AM

It depends on what discharge level you choose. Lets say you operate 24 Volts battery between 20 to 24volts,

Max current your Motor will draw is 4000/24=166.666

So the amount of charge required to run motor for 2hrs = I x T= 167 x 2 x 60 x 60

= 1202400 Coulomb.

Min discharge level =20 Volts

%Age coulombs available for motor ={(24-20)/24} x100= 16.66%

So the total amount of charge required inside the battery

= 1202400 / 0.1666=7214688 coulomb

Total Amp-Hr required = 7214688 /3600 = 2004 Amp-Hr (1amp hr = 3600 Coulomb)
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mark
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#3
In reply to #2

Re: capacity calculation

11/03/2008 10:15 AM

Good learning for me, My GA.
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Bill
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#4
In reply to #3

Re: capacity calculation

11/03/2008 2:19 PM

And 1 Coulomb = 6.241 509 629 152 65×1018 electrons . . .

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ganapa
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#6
In reply to #2

Re: capacity calculation

03/03/2009 3:29 AM

thanks Rakesh, all these days I though calculation of AH is to just multiply the current drawn with the no. of hours.

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MultiTech
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#5

Re: capacity calculation

11/15/2008 3:03 AM

well done guys, it is a good learning for me too,

normally I'll just multiply the current by the time and get the AH ( ampere hour )

Thanks

William Tan

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