That's weird, I don't recall what the first set of batteries that were in the one I sent back, but I popped my open earlier due to this discussion and their Li-Ions rated the same 2450 mah! Maybe the low cost one in Amazon does use NiMh's and the more expensive doesn't? Either that or Phillips is having different sources build to different specs, or perhaps Phillips decided to use a cheaper costing battery because mine is 2 years old? but they never changed their website read this: http://www.mea.philips.com/c/bicycle...specifications. But regardless the NiMh is rated for the same 2 hour/8 hour run time.