The Chevy Volt has batteries that split down (without a headache) into 7x 12s3p packs and 2x 6s3p packs. Lvl1 hackerspace, In Theory Racing, and Lazy gecko, to name a few, have raced with Volt batteries before.

here is a link to a Lazy Gecko tear-down of a 12s pack to the cell-level: http://forum.teamlazygecko.com/viewtopic.php?f=15&t=44

MakerFX Makerspace Chevy Volt Battery Documentation: http://wiki.makerfx.org/Chevy_Volt_Battery_Documentation