nc8430 Extended Battery question

OK, so while I eagerly await the arrival of my nc8430 I figured I'd plan out what accessories (in addition to the adv. docking station that's already arrived and looking lonely) to buy.

I noticed while perusing the HP website that there are several different batteries listed for the nc8430.

So far I only will have one of the 8-cell primary batteries. Do the 8-cell extended life batteries attach to the laptop at the same time as the primary battery? (IE have 16 cells of batteries attached to my laptop at once) As far as I can tell that's what the 'Ultra capacity' battery does, the laptop basically docks on top of it (the 12-cell battery). Or is there some way to attach all three have have 38 cells at once?

 

Looking here, the extended life battery actually has lower Whr (total energy stored) rating than the 8-cell primary (52 Whr vs 69Whr) so I must assume that you do put both of them on the laptop at once (which lines up with the life HP expects out of each config (4 hrs with primary and 7.5 hrs with extended)

 

yes, the nc8430 has the capability to use two batteries. there is a port on the bottom of the notebook where you can hook up the second battery.