Battery upgrade?

I recently bought my first laptop, to be able to travel. It is an Aspire 7551G.
I will use it maily for mail, notes and watching movies and vids that I have on a separate 2TB drive. The laptop runs quite cool, close to 50 degrees C, but I also have a cooling pad should I need it.
I am getting about 2 hours to 2 hrs 15 minutes before my warning comes up to plug in.
My question is: I have seen replacement battteries for this machine that have 9 and 12 cells. The voltage and mA ratings are slightly higher. They are offered as direct replacement for the six cell currently installed.
1) Is there any reason not to use one of these, in terms of computer damage? and
2) Can I expect any significant improvement in my between charge times?
Sorry if this is a really basic question, but unwilling to spend more if it will not be an improvement.
thanks,
m.

 

Hi,

in theory, a battery with twice the capacity (in Wh) should give you double battery life.

The problem: With aftermarket batteries, you don't know what you get, quality wise.

Michael

 

All Acer machines to my knowledge can take high voltage batteries that fit in the battery bay.

Some times it can be a bit odd.

I had a battery (high voltage) that worked perfectly well in a 5935G that came with the low voltage battery. However when placed in this 7738G it would not charge it, it ran off it fine, but would just stay on not charging, even though this machine ships with the high voltage battery :/