P3020 Battery block 10 gets weak

Working on a friends 2012. He bought this car with a bad ABS unit and it took us several months to replace it. Prior to the ABS repair the car had no battery codes and would operate in EV mode, now it constantly runs and won't go into EV mode. Now that we finally replaced the ABS unit, scanning shows:

Current P3020 Battery Block 10 gets weak

Pending P0A7F Deterioration of hybrid battery pack

Pending P0A80 Replacement of hybrid battery pack

The ABS/VSC/TRAC shows:

Current C1259 Regenerative malfunction of HV control system

Current C1310 Malfunction of HV system

I think this car ultimately needs a battery replacement, but I was wondering what should I do/check before he goes and shells out a bunch more money for a battery.

I'm thinking I should check for corrosion/damage in the voltage sensor ECU. Check for corrosion on the bus bars. And maybe try to equalize the cell voltage??? I can do all that for little to no cost. But, I don't know if its worth spending money on multichannel hobby chargers to try and fully recondition an old battery. Maybe I should also check and see if there is a date on the battery to see if its ever been replaced?

Any opinions, tips or advice is appreciated.