Yes, but only if the power supply design of the laptop allows it, because the charge controls are dependent on the battery. Ask the manufacturer first.
The number that you refer to is the ampacity of the battery. The higher the number the longer the battery will operate in the device. As long as the voltage output of the two batteries are the same it will not ruin your laptop.
Yes. The larger capacity means that it will deliver charge for (very slightly) longer than the other one.
Not really. 6000 mah means the battery has a capacity of 750 (6000 / 8) ma for 8 hours, while 7800 mah means the battery has a capacity of 975 (7800 / 8) ma for 8 hours.
to boost your ;laptop use registry cleaner reg in out
! kw = 1000 watts 7800 kw = 7800 x 1000 watts = 7800 000 watts
It usually means an upgrade to a 9 cell battery with (theoretically) double the usage time, but that obviously isn't an exact science, but it is a decent rough guide
7800
21% Divide 1640 by 7800 to get to the answer → 0.2102564102564103 1640/7800=0.2102564102564103
7800
7800
7800
7800 / 2 is equal to 3,900.