Is the battery pack used in the iLiad changeable by the user? Which battery is used?

No it is not user changeable...it is apparently a custom battery, not a generic model like the one the Hanlin deivces use.

Henrycat answered this a while ago. iRex was then still pondering how they should handle broken batteries.

Mhm... Bad news especially for us early adopters without finished power management...

Well, it would have been a very smart thing, to include an easy way to change the battery. Even bettery, to use some existing battery format and use that. But i do not know, how much energy is stored in the batteries used now in the iLiad, anyone knows?