How to calculate the AH capacity of a battery?

[Stephenk53]

Summary

I made a vinegar battery that appears to only output .001A of current. I made it very quickly because I had to change my design for a project last minute due to my inability to get a voltage regulator in time. So it is so bad I doubt I could have made a worse battery. Anyway, the project was a rechargeable flashlight and it has already been graded which is why I am not putting this in a homework forum. So how would I find out its mAH rating? I would like to know for knowings sake rather than actual need so if I have to fully discharge the battery to do so that is fine.

Questions
How to calculate the AH
How would I lower the resistance in the battery?

 

[NascentOxygen]

Hi Stephenk53.

If you connect your battery to a load, and include your mA meter in the circuit, then record the meter's reading at regular intervals and plot a graph: mA versus time (in hours). The area under your curve will have units of ...?

What are your thoughts on how you might go about reducing the cell's resistance?

It still belongs in the homework subforum because it resembles typical homework.

 

[Stephenk53]

To reduce the resistance I thought I could move the cathode and anodes of the cells closer together within each cell, although that would reduce voltage but I could change that by increasing surface area of the cathodes and anodes. I could try adding something that is a powdered conductor such as salt into the vinegar or metal powder of a different material as the cathodes and anodes. But if I add a conductor of some kind I would think that would affect the voltage in some way.

As for recording the mA I think I would have some sort of camera record a constant reading from the mA meter to keep track of possible spikes in the readings.

 

[NascentOxygen]

To reduce the resistance I thought I could move the cathode and anodes of the cells closer together within each cell

That is a reasonable thing to try.

although that would reduce voltage

Why do you think that might happen?

but I could change that by increasing surface area of the cathodes and anodes.

That is another change you could investigate, it may achieve what you are hoping. As might a different electrolyte, or maybe just a more concentrated version of the electrolyte you are using.

If your setup is not disturbed, there should not be any abrupt changes in current, just a gradual reduction as your battery goes flat.

 

[David Lewis]

The less current you draw, the more capacity the cell will have. Note that AH (or more properly A-hr) is a unit of measure. Charge capacity is the corresponding physical quantity.

 

[Stephenk53]

Why do you think that might happen?

I think it would happen because that is what appeared to occur when I had moved the cathode and anodes when I was resealing one of the batteries that had a leak

 

[NascentOxygen]

I think it would happen because that is what appeared to occur when I had moved the cathode and anodes when I was resealing one of the batteries that had a leak

It may have been a loose lead. Movement of electrical connections is the cause of a lot of problems.