Thanks, that's what I thought.

No not if the"Y" lead means both packs are in paralegal, ie if the output voltage from the Y lead is the same whether one or 2 packs connected. The charger can't determine which pack is full or not. if in series it's fine, however you'd need a charger capable charging the total Vols across both packs. For example 2x 7.2v packs in series needs a charger capable of 14.4v or as they usually state 12cells. Not sure they would charge any quicker like this. Better having more than 1 charger if lack of time is the issue. I have 2 multi, 1 gell and a dedicated lipo charger.

Short answer no you can't charge in parallel , which is what you are proposing with a y lead ....but if they are the same capacity (Mah) you can charge them is series....all to do with the resistance in each cell.
Some more here....http://www.rcgroups.com/forums/showthread.php?t=2102404

hope that helps.