Huh - to answer my own question - you remove it by pushing a thin rod through a hole on opposite side to LCD.I too got the new Hahnel with my IQ4 - but in that link you see a AA plate that is included - do the plates come out of the Phase version of the charger, so you can swap plates, and if so... how?!
A bit like when you remove cellphone SIM card. (image below). Pops out and up.
All other Hahnel's (for Canon, Sony, etc) come with an AA tray, but Phase does not supply it, and I can't see where to buy this alone, or other trays.
I still think the Watson/Prospec one is a superior solution. Wide range of light & small trays available, high-tech charging. Best if you have more than one type of battery to charge on a trip.