# Stored Charge in a Battery

1. Jan 15, 2012

### Lildon

1. The problem statement, all variables and given/known data
Which of the following batteries has the most stored charge? Their ratings are shown below. Explain your answer.
a) 12V, 500mAh
b) 1.2V, 1200uAh
c) 6V, 3.14159x10e17 electrons
d) 6V, 0.01MAh

2. The attempt at a solution
I think the answer is d because 0.01MAh = 10,000Ah. I'm not sure if this is even right or how to explain it. I haven't really been taught anything about this and all of my experience is from searching the internet for information.

Last edited: Jan 15, 2012
2. Jan 15, 2012

### sandy.bridge

Hint: the higher the ampere-hour, the longer the battery will last.

3. Jan 15, 2012

### technician

The question asks which battery has the most charge.
Ah means Amps x hours which means (coulombs/sec) x hours
which gives charge = (coulombs/sec) x hours x 60 x 60

4. Jan 15, 2012

### Lildon

That means the answer would be D because it has the highest Amp-hours. So the amount of volts has no affect on stored charge?

5. Jan 15, 2012

### Staff: Mentor

There are a few things about this question. First, electrochemical cells don't store charge, they store energy in the form of chemical energy. But I know what they mean.
Second, it is obvious here (I think), but often ratings are printed carelessly, and M may sometimes stand for milli-, you can't always assume manufacturers mean mega-. To manufacture a battery rated at 10,000 Ah would make it a colossal size. Maybe something from a submarine?

Volts is not a measure of the current you can draw, in the way it's meant here. So it is only amp-hour capacity that you need to consider.

6. Jan 16, 2012

### technician

I agree.....voltage has nothing to do with the amount of charge that can be obtained.
Ah tell you how many coulombs of charge are available.
Voltage tells you how much ENERGY can be obtained per coulomb