Not charging enough?

The car spent has now spent over a week with the battery in and it works fine.

Over the 6 days when it was connected and not driven the voltage dropped was 12.7 to 12.4 volts.

It started perfectly, and terminal voltage was 14.3V at idle immediately after starting.

The car had a number of 30min+ drives on Saturday and Sunday, which I would have though was enough to fully charge the battery.

After I washed the car on Sunday I connected the battery charger, and it took about 1 hour to raise the voltage to 15v at which point it drops to a 13.6 holding voltage.

Does this mean the battery is only at 90% charge when the car is driven? If the battery is never becoming fully charged through driving this could be a potential cause of sulfation and battery failure. Although if it had sulfated, would it have recovered fully as it now seems to?

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