High voltage across my main battery pack

I've replaced my main battery once over the 170k miles on my gen II Prius. I recently had a cell go bad so I bought a used one on eBay.. all seemed good, however, I noticed a few things that seemed puzzling. 1. After dissembling the battery pack and removing the one bad battery, I noticed the voltage seemed to increase across all the batteries. They were sitting at the 7.4 mark at the time of removing the onc bad cell, but after a day of sitting on the bench, I went back and checked the voltage and they all were sitting at 8.2 - 8.4 volts. I'm not sure if I should discharge them, or is this pack just running high - and that's okay. Any thoughts?