I have a question and hope that you can help me.

There are these battery adapters that take e.g. three smaller cells (e.g. AA) and form a battery of a larger format.

Like that one:

The batteries can be parallel or in series.

For the parallel kind, what happens if the batteries inserted have very different voltages, e.g. two are full and one is empty?

Or what happens when using rechargable batteries with different sizes, e.g. 1.2 V 1300 mAh and 2000 mAh and the smaller one is depleted earlier?

Or if you combine a 1.5 V non-rechargable with a 1.2 V rechargable one?

There are battery adapters that take e.g. three smaller cells (e.g. AA) and form a battery of a larger format.

Like that one:

The batteries can be parallel or in series.

For the parallel kind, what happens if the batteries inserted have very different voltages, e.g. two are full and one is empty?

Or what happens when using rechargeable batteries of different sizes, e.g. 1.2 V 1300 mAh and 2000 mAh, and the smaller one is depleted earlier?

Or if you combine a 1.5 V non-rechargable with a 1.2 V rechargable one?