I suspect what we are talking about is not necessarily an issue with charging the battery because it's low, but moreso some extra built in logic in the computer that decides E-mode at this speed coupled with A/C often not a good idea because either:

* draws too much power
* less efficient that running ICE overall
* arbitrary limit set by Toyota engineers
* prevents something bad happening
* insert your own idea here...

Two climate control systems, one inside and the other at the tailpipe.

2007 Camry Hybrid (in service June 2006)
FE: 6.77L/100km (34.8 mpg) over 37750km (23450mi)
75% city - Ave trip 20 min - 2 Winters