# not got much time left

• Aug 22nd 2013, 04:26 AM
fatherjack
not got much time left
if a battery has a capacity of 2510mAh and it draws a current of 1.53mA how long will it take before the battery either has be replaced or recharged answer in scientific notation please
• Aug 22nd 2013, 05:43 AM
HallsofIvy
Re: not got much time left
Do you mean "not much time left until the battery is discharged" or "not much time left until I have to turn this in"? If the former, why not just wait until it is discharged and see? If this is class work why have you not tried anything yourself? Do you not know what "mAh" and "mA" mean? If you do, what operation you need to do should be obvious!

(If you have to drive 100 miles and are averaging 50 miles per hour, how long will it take? Do you understand what arithmetic operation you need to do? Do you see how this is conntected to your problem?)
• Aug 23rd 2013, 05:48 AM
fatherjack
Re: not got much time left
thank you for your help I've been struggling on this and I've lost confidence in myself and just need to check my own answer that all thank you once again
• Aug 23rd 2013, 08:24 AM
Paze
Re: not got much time left
I would start by converting the mAh to Coulombs.

One Ah is 3600 C so one mAh is 3600/1000 = 3.6 C, correct?

So the battery has a capacity of 3.6 Coulombs.

Let's remind ourselves what an ampere actually IS. An Ampere is the equivalent to one Coulomb per second.

So what does 1.53 mA mean? If it were 1.53 A it would be 1.53 Coulombs per second. But it's mA so we divide by 1000. The battery draws 1.53/1000 or 0.00153 Coulombs per second.

So we have a battery with the capacity of 3.6 Coulombs and it draws a current of 0.00153 Coulombs per second. I'm sure you can figure out how many seconds the battery takes to draw to full (or empty?).
• Aug 23rd 2013, 08:45 AM
HallsofIvy
Re: not got much time left
Quote:

Originally Posted by fatherjack
thank you for your help I've been struggling on this and I've lost confidence in myself and just need to check my own answer that all thank you once again

Then tell us what answer you got!