A bit more:

[Resulting from Endeavour's planned refit, STS-118 will mark the debut of an upgraded power distribution module, the Station-Shuttle Power Transfer System (SSPTS). SSPTS allows Endeavour to operate from ISS power supply, converting up to 8 kiloWatts (8kW) of electrical power from 120-Volt Direct Current (120VDC) ISS main voltage to the 28VDC system used by the Shuttle Orbiter. SSPTS was outfitted to the ISS Pressurized Mating Adapter 2 (PMA2) during STS-116. These upgrades should allow the Orbiter to remain docked at the station for an additional 3-4 days each mission.[1][2][3]

Answers.com

Let's just hope that there won't be any computer problems next time or the orbiter will have assume similar duties (attitude control...) as with STS 117.