[COLVERT]

Analogy for some clarity about battery capacity.

Two tanks of water side by side.
Both a metre in depth.
One tank a metre in diameter and the other ten metres in diameter.
Let the depth be the voltage ( 12 ) and the diameter be the capacity. ( Amps. )

Obviously the larger tank has the greater capacity but the depths ( voltages, are identical. )

It's possible to have two batteries with very similar voltages but, as the tanks described above, to have totally different capacities.

It's the capacity that's needed to do the work.

The starter motor is 12 volts but needs something like 150 amps to spin it. As a battery ages it loses capacity until it reaches the stage where it can't do what you want it to do.





PS. At my age I have intimate understanding of that feeling and it makes my wife very happy to keep telling me so.--