Why the internal resistance of battery is greater than internal resistance of car's accumulator?
Size.

The surface area of a car's battery / accumulator is many, many times that of a AA battery. This, along with the chemistry lowers the internal resistance of the battery.

In addition, the car's battery is designed to have low resistance to enable it to deliver high currents for the engine starter motor.


  In my opinion it is caused by the fact that the battery is not as accurate as car accumulator.


I think there is a language problem here. Batteries are not "accurate". The output voltage is a function of the chemistry, size and design.