Replaced hv battery and still get vsc , check engine and red triangle light

Good evening to all. I am reaching out to someone for desperate help. I have a 2009 Toyota Prius with 170k miles on it. Recently as I was driving the red triangle of death came on as well as the check engine and vsc lights. Went to oriley to get it scanned and the guy that worked there told me it was due to the hv battery failure. Looked on YouTube to see how to find out which cell/cells went bad and how to replace them. Checked all the cells they all red 8.0 except one of them red 6.7. In the video they say if it’s below 7.0 it needs to be replaced. I got a used cell from a junkyard for $65 and when I tested it it was 7.6. I then put it in and the car ran good until an hour later all the lights came on and the started losing power. I then cleared the lights and the car was running fine again. The Next morning I turned on the car and the lights were back on then the battery went completely dead. What’s causing the battery to drain? What did I do wrong? I know all the cells are good. I filled up the coolant because it seemed a little low. My only other theory is that the coolant adverter pump is out but how can I know that? And if I do decide to replace the pump what if the lights turn on again. One more question. Since the battery drained again does this mean atleast one or more cell went bad again?

 

Thank you for the help. I was talking about the hybrid battery went completely dead. Also I did make sure I did the 3rd step by clicking the orange switch down. Today I replaced the hv battery ecu and the red triangle and other lights came back. It’s driving me crazy. I don’t know what’s causing the red triangle to come back. I tested the overall volts for the battery and it was 222 volts. Do you know if that’s enough to keep the car going?

 

I’m in the Bay Area. I did feel for the pump and felt vibration