hey guys, my guess is they are using a DC->DC convertor to get a bipolar output from the 4.2 battery, as such there is very little difference in the battery. a 4.2v 4800mAh is equal to a 8.4v 2400mAh, then some losses for the DC convertor and there is very little difference. the batteries will be practically the same size so it wont be bigger.
the opa627 and buf634 would not survive on 4.2v/2 (+/-2.1v) so there is a charge pump or DC-DC convertor there somewhere. truth be told even +/-4.2v is marginal; particularly as all of these battery voltages are nominal voltages, so they will be higher fully charged and considerably lower at the end of charge.
Edited by qusp - 8/22/12 at 8:54pm