New Hybrid Battery gone bad?

You need data to show them... If you do a load test on all 28 modules you'll be able to identify the one that's causing the problem. All you need is a timer, a multi-tester and the headlamp bulb. Here's how to do it: Prolong® Battery Module Load Tester User Guide – Hybrid Automotive You can also use the resistance and voltage readings via the Torque app via OBD2 Bluetooth reader.

For them to say the car has to throw codes to do a warranty is BS. If you spend $2000 on a part that is showing signs of being defective and they refuse, go direct to Toyota customer service and keep escalating to manager, supervisor, etc until you get results. At the very least you need to document all the signs of early failure, so when it does throw a code you can prove the problem started before the one-year warranty expired.

 

I would try to find someone, e.g. a dealer or someone else, who has the TechStream diagnosis software from Toyota and is able and willing to check the HV-battery ideally under heavy load, e.g. in EV-mode driving. Differences in voltage between modules can then be identified easily.

 

who installed it? dealer installation includes 3 year warranty.

of course, anything is possible, but extremely unlikely. how is it behaving with the new 12v, and did you charge the 12v before installing?

the hybrid battery charges the 12v, but not while the car is off. it should not be dropping 5 bars overnight.
that said, how are your mpg's?

 

The likelihood of a NEW battery failing within a year is very, very small.

 

If 2 dealers have checked your car and determined the HV battery to be in good health, then you probably don't have any problems.

If it's really hot out and you're blasting the AC, your car's battery State of Charge will go down much faster than normal. That does not mean there's something wrong with the car, just that it's hot and it's using up energy faster

 

I read the starting post again:
Turning off the car with a "normal" State-of-charge" (SOC), e.g. 5-6 bars, and startting it again next day with only 2-3 is quite normal if you have used EV-mode or AC before turning the car off. SOC is a calculated value and sometimes the calculation is too slow to show the real charge level in time. In this case I would not worry at all.