Battery at 63°C (145°F)

My wife drove down the hill in B gear, AC on, battery was at full charge, then we stopped for dinner. Car was parked for an hour or so, outside temp was around 25°C (77°F). I then drove back up the hill and it sure felt strange, accelerator pedal input was non linear, car would not cooperate going up the hill like normal. I then ran Android app on my phone and nearly had a hart attack, battery temp was at 63°C and there was no meaningful power going from/to the battery. Battery fan was running at max level and when battery was bellow 50°C I got normal operation of around 8 kW from the battery.

I have newer experienced something like that, until now I was always under 50°C even when on full charge going down the steep hills.

One other thing about the battery, battery lines when charged from empty (2 bars) to 6 bars is then discharged in very linear fashion, but when the battery gets to full 8 bars, then when discharged and it gets to 4 bars it then jumps to 2 bars no matter what you do, even at steady speed with ICE ON and showing charge TO the battery.

Car will be 8 years old, I'm extending battery warranty with each service until the car is 10 years old (it's a EU thing). Now I'm hoping it dies within two years I will report back to this thread how this pans out.