This is an interesting mod, and it’s unfortunate that we don’t have all that much documentation on it. The person who performed the mod did not take photos of the procedure, but only described it afterwards. But in the end, he got a 3,300 mAh battery into a Motorola Atrix HD body, without any extensions or custom battery covers. This nearly doubled the 1,780 mAh battery that is installed in the Atrix HD.
Note that this is a VERY dangerous procedure. It requires you to strip plastic out of the inside of your phone, after disassembling it. Do this at your own risk, and we are not responsible for any broken phones or severed fingers.
If you want to try this out, hit the source link. The only downside is that the phone doesn’t show a proper battery percentage due to not having voltage mapped to percentage correctly on the new battery. It isn’t broken by any means, it still shows a decent representation, but it could be off a bit. Otherwise, it lasts about twice as long. Adventurous? Go try it!