• johnsmith12345
In summary, the capacity of a AAA battery can vary greatly depending on the discharge current. At a low current of a few mA, a AAA alkaline battery can deliver around 1200mAh, but at a higher current of 1A, the capacity will be significantly lower. This is why alkaline batteries are not ideal for high-powered devices like digital cameras. NiMH batteries, like eneloops, have a more consistent capacity at different discharge currents. However, measuring the true open circuit emf of a battery can be difficult without opening the circuit, so it may be more practical to periodically measure the no-load voltage while maintaining a constant load current. Overall, the open circuit emf is not typically used in discharge curves, but it
johnsmith12345
I am trying to find the capacity of a AAA battery by discharging it. How would I be able to discharge the battery at a 1A current so that I don't have to wait for a long period of time?

How would I be able to discharge the battery at a 1A current so that I don't have to wait for a long period of time?
... pick a low capacity battery.

I was actually inquiring more about the constant 1A current discharge bit.

Ah - not the time part.
Use Ohm's law and pick an appropriate resistor.

You realize that the discharge current affects the capacity?
If it's discharged at just a few mA, a AAA alkaline battery can deliver around 1200mAh. However at a current of 400mA the capacity is only 400mAh and at 1A it will be even much less than that. That's why alkaline batteries are really bad for digital cameras.
http://data.energizer.com/PDFs/l92.pdf

DrZoidberg said:
You realize that the discharge current affects the capacity?
If it's discharged at just a few mA, a AAA alkaline battery can deliver around 1200mAh. However at a current of 400mA the capacity is only 400mAh and at 1A it will be even much less than that. That's why alkaline batteries are really bad for digital cameras.
http://data.energizer.com/PDFs/l92.pdf

Well I'm actually using a NiMH battery. It happens to be one of those eneloops so looking from the data sheets on their website, the capacity doesn't decrease a lot with an increase in the discharge current.

The only problem I am facing now is that I can't measure the true emf acrosss the battery at the same time I am discharging it. Does anyone have a solution?

What do you mean by "true" emf?

Simon Bridge said:
What do you mean by "true" emf?

The emf of the battery without connecting it to any resistors.

Well, there is no way to measure the open circuit emf without opening the circuit.
You could just throw a switch.

What do you need to know that for though?
You may want to see how the internal resistance varies as the battery loses energy.

Well I need it so that I can get enough data about the open circuit emf to plot a discharge curve.

http://www.powerstream.com/AA-tests.htm
http://www.mpoweruk.com/performance.htm
... I don't see anyone using open-circuit voltage for the discharge curves - but you can just open the circuit periodically to measure it. If the internal resistance is fairly constant, you can calculate the open-circuit voltage from the closed circuit one. You'll want to keep the battery at a reasonably constant temperature though.

johnsmith12345 said:
Well I need it so that I can get enough data about the open circuit emf to plot a discharge curve.
I think you'll find that the open circuit emf is generally not of much interest. (Though maybe you have a niche application where it is.) You should check that you are required to plot the no-load voltage, as that would be unusual. Most common would be a plot of load voltage vs. time while the load current is maintained at some specified constant level.

I think for common types the no-load voltage changes very little, once past the initial drop.
Immediately after the cell has its load removed the voltage takes some time to rise and reach a steady value. Do you intend allowing your cell time to recover before measuring your no-load voltage?

## 1. What is the purpose of an experiment about discharging batteries?

The purpose of this experiment is to study the process of discharging batteries and how it affects their performance and overall lifespan.

## 2. What materials are needed for an experiment about discharging batteries?

The materials needed for this experiment include batteries (of the same type and brand), a battery tester or voltmeter, wires, a resistor, and a stopwatch or timer.

## 3. How do you set up an experiment about discharging batteries?

To set up the experiment, connect the battery to the resistor and voltmeter in series. Start the timer and record the voltage readings at regular intervals until the battery is fully discharged. Make sure to use the same type of battery for each trial and repeat the experiment multiple times for accurate results.

## 4. What are some possible outcomes from an experiment about discharging batteries?

Some possible outcomes from this experiment include a decrease in voltage over time, a shorter runtime for the battery, and a decrease in overall battery capacity. These results can vary based on the type of battery and the discharge rate.

## 5. What are the potential applications of the findings from an experiment about discharging batteries?

The findings from this experiment can provide valuable information for battery manufacturers to improve their products and for consumers to better understand the performance and lifespan of different types of batteries. It can also be used to optimize battery usage in various devices and applications.

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