The biggest problem when upgrading the T3 battery to even higher capacity, however, is that there is limited space within the handheld shell for a larger battery. Hence, modification typically requires some crushing of the replacement battery to make it fit and/or irreversible modification to the internal components of the shell (for example the stylus holder). Another problem is that Lithium-Ion batteries require a regulator circuit to regulate battery charge preventing damage, and so replacement batteries either require a built-in one or a grafted regulator circuit added.