Replacing a battery from another tablet

ASUS t300 chi

I'm into sort of an idea where at least replacing a battery in your tablet by the same brand could work (sounds more promising).

By some research (ASUS forums & battery vendors) on the web, the main problems that would turn up is:

- Battery wont charge after replacement

- The control system in the device monitoring the output would probably disagree

- Physical size of the battery

Why this question arrises is because I just bought the ASUS T300 Chi since the battery time on this device is only about 4 hours. At the same time I got my >~ 1 year old ASUS T100ta that I really liked, though it has felt quite slow. By specs I have so far found out that:

T300 Chi - ~4000 mAh, 33 kwh, 7.9 V (assumes that they mean 2 cells in series since Li pol. only operates at 3.3 or 3.7 < 4.2 V)

T100ta - ~8000 mAh (!!!), 33 kwh, 3.8 V (sounds more likely!), 2 cells

This is why replacing the battery in the T300 Chi with my old T100ta (150 of 500 recomm. cycles used up so far) is of great interest.

So any ideas?