Car sat for 18 months. Dead cells in battery?

is the 12v okay? where did you get the new cells? 18 months is a long time to sit

 

Inspect the HV battery 'voltage sense harness' for tab/wire corrosion, and the HV battery ECU socket for pin corrosion.

Take pictures and post them here if unsure. How far from Columbia SC are you?

FYI : You're moderated until you've posted 5 times.

 

It's very likely those modules are dead due to corrosion in the ecu socket where the voltage sensing harness plugs in.
Unfortunately, it's not uncommon for batteries that have sat for long periods. I see it in quite a few core batteries that have sat at a salvage yard for extended periods.

 

I'm seeing a similar Dr. Prius output where all of the voltages were fluctuating wildly on a car that had probably sat for a similar length of time to yours. However, after replacing the 12V battery that could not keep a charge, it did allow me to drive the car for a few months, even with fluctuating voltages. After the temperature dipped below 60 degrees this winter, the car would no longer get to READY. I took my HV battery out and the modules all measured 7.88-7.89 V. I did discover that my #1 voltage sensing wire had completely snapped, but I couldn't be certain if that happened during the disassembly. I have not put it back into the car yet, but I'm hopeful resoldering the voltage sensing connector and replacing busbars will help things.

I would also recommend examining the voltage sensing harness and the ecu socket for your battery.

 

Test individual cells w dig meter. Clean bus bars if corroded. Recharge cells w charger if needed

 

You don't have to replace the bus bars so come in clear vinegar and baking soda and scrub with a nylon brush