Well, maybe some EE guy can help more with that, but a search for your model number pelt turned up a few interesting threads, I only skimmed but in the OC one it is suggested that ~7 volts may be the peak efficiency for thermochill enterprises pelts?
http://www.ocforums.com/showthread.php?t=373496
http://www.xtremesystems.org/forums/...d.php?p=944104