edit: apparently Batterymon can tell you what kind of battery you have, so try that (free 30 day trial, $24 to purchase) if it doesn't, it should tell you your batteries wear level (fully charged / designed capacity)
the panasonic seems to start with a wear level of ~9% whereas the sanyo starts with a wear level <=5%
supposedly if you're still under warranty and experiencing high battery wear, you can contact Acer and they'll replace your battery with a sanyo
the battery in most notebooks is easy to remove.
the battery in your notebook is not (normally done to save space and provide a larger battery that may be oddly shaped).
edit: doing the following will void your warranty
most likely you'll have to remove multiple screws and then probably detach the screen to open the case, and then if you're really unlucky you might have to remove the keyboard (that would be kind of stupid design wise though).
http://broo2.blogspot.com/2011/07/acer-3830tg-6431-teardown.html
that post explains how to open your notebook up
http://forum.notebookreview.com/windows-os-software/40373-check-your-batterys-wear-leve.html
battery wear level thread