How to open Sharp Mobilon battery?

I finally got a color sharp Mobilon. I thought I had asked if the grayscale's AA battery holder fit on the color ones and I thought the answer was no, but it fits perfectly fine, the only difference is the contact is at a different place. I'll try to mod the AA holder from my defective grayscale Mobilon to work on the color one, that would be perfect having a color HPC that runs on AAs and theres no reason it wouldn't work.

In any case, how do you split open the rechargeable pack? I tried but was afraid the plastic would break at the wrong place, is there a trick or instructions somewhere?

By the way I finally found that the backlight button does on the color Mobilons, it simply toggles between two brightness levels, I had asked a few times before and no one seemed to know.

Thanks