At about 20°C, there has been a situation that the OEM battery in my '08 Jetta was not capable of starting the car at all (virtually no movement of the starter at all), after being used for at least an hour to charge a cell phone and open/close the power windows with the engine not running.
However, leaving it alone for some 15 to 30 minutes, and the car started just fine.
Why does this happen? I thought the surface charge is generally only something that is positive compared to the overall condition of the battery.