But remember that the number of electrons stored in the thing is actually determined by the raw size of the cell and area of the plates, not the number of cells that determines the voltage. Now if you connect the anode and cathode of a charge battery with an electric gadget, like a trolling motor, the electrons flow through the gadget at a rate proportional to the resistance of the gadget. An open circuit, which has almost infinite resistance, results in no flow and the battery stays charged .A short circuit, which has almost no resistance, results is a drastically rapid flow that can melt things. As the elctrons flow from anode to cathode the chemicals in the battery return to their uncharged state. If you double the voltage by using two cells you would double the flow of electrons assuming that the gadget's resistance is unchanged.
Amperage is a measure of how many electrons are flowing through the wire.
In fact one horsepower is about 750 watts, easy to remember. So if you could put an ammeter and a voltmeter in the circuit to measure the current and voltage of the the juice flowing through the gadget powered by the battery, you could know the power it is taking in. If you make the comparison to a gas engine, you might say the electric motor has a certain power and that the battery is like the gas tank. So the question is how much power is stored in the battery. It's is done by multiplying the amp-hours times the voltage.