I suspect the answer to this question - "Is it possible to make up some sort of circuit that would allow you to vary the Ah provided by a battery?" - is "NO, Not Possible" but here goes.
I want to test a device with varying Amp Hours from a rechargeable battery.
For example, I have a fully charged 4.5Ah battery but I want to make it look like it only has 2Ah or 1.5Ah or some other value under 4.5Ah - is that even possible? I'd recharge the battery before each test.
In effect, I want to limit the time the device would operate before the battery was exhausted by altering the Ah of the battery.
This is sort of like using a timer to control the time but that does not meet my requirements. I want the device to operate until the battery is exhausted and I'd like to determine times vs Ah so that I can substitute a battery with an appropriate Ah rating for the approximate time I want the device to operate.
If this is possible, can you give me at least an idea of the circuit needed?
Or - Can a power supply be constructed on which you could not only set the voltage but also the Ah it would provide before shutting off power output? That would be another way I could do what I want to do.
It would not actually emulate a battery in that it would produce a constant voltage where as a battery's voltage would decrease with use but it would be a way to at least approximate what I want to do - if my first idea of varying the Ah of a battery is not possible.
Perhaps a device to measure the amperage draw and time and calculate the Ah and shutoff power to the device at a set Ah value??
This is all probably quite impossible. I may have to get batteries of the correct voltage with different Ah and just time how long the device operates with each battery.