You did it right. The module with only 6.4V has one of its internal cells permanently shorted. Unfortunately a shorted NiMH cell is a permanent failure. That module cannot be fixed or reconditioned. The “nominal” voltage of a single NiMH cell is roughly 1.25V. One Prius “module” contains 6 cells in series. Note that 6 x 1.25 = 7.5V. But with one cell shorted, then you get 5 x 1.25 = 6.25V. When one internal cell in a Prius HV pack shorts out like yours did, then the car will immediately have a P0A80 emergency code and change into “limp” mode where you can still drivevery slowly. Clearing the P0A80 won’t help because it will throw the same code again if one internal cell is actually shorted. For monitoring the state of your partially restored HV pack I recommend using the Torque Pro (Android app) along with a decent quality OBDII Bluetooth adaptor. I have these items and they have worked perfectly for me. -Greg
Did you see the Wiki section at the top of the priuschat screen? Check there for the Wiki I wrote/started on How To/ "Maintenance" under repairing the HV battery. Here's the link: Prius High Voltage Battery Reconditioning | PriusChat