No-start condition. Seems like 12V, but dealer tested 'good.'

Hello,

I am currently having an intermittent no-start condition - well no-READY condition - when pushing the power button, and I wanted to get your thoughts.

Just talking 12V battery in the below, not the hybrid battery.

Long story short: car has run fine and suddenly wont go into 'ready' mode, with no other issues or faults. The same thing happened in 2024, and when I researched the issue then, I found a post recommending to check the 12V battery. In that instance, the battery turned out to be bad, and I replaced it with genuine Toyota.

This time around I checked the the battery, and it was showing 11.7 volts, so I took it to the dealer. They tested it and said it was good - much to my surprise!

They gave me a little ticket that states the following:

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GOOD BATTERY

Customer Complaint: Yes
Charging Required: Yep
Charging Completed: Oh yea
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Reserve Health: N/A

Cranking State of Health
----------------|---|-----------------
Replace_____________Good

(the formatting didnt come out great on this but its supposed to be a bar that shows the health state smack in-between Good and Replace)
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Voltage: 12.85 V
Rated: 325 CCA
Measured: 339 CCA
Ah Replaced: 42.5 Ah
Time to Decision: 00:51:55
Charge Time: 01:36:12
Temperature: 77 F
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This tells me that they had to charge it a fair bit to get it into normal range, and that after that the load test went well. Initially I was suspect that the DC converter wasnt charging the 12V battery properly, or that there was a parasitic drain.

When I got home, I put the battery back the in car, and it started normally - but a few moments later the red triangle came on. I plugged in the OBD reader and monitored voltages and temps. Everything seemed normal, also no fault codes, so I cleared the red triangle and drove around in the parking lot while keeping an eye on everything. The car drove normally and the inverter was delivering a rock-steady 14.0 volts to the 12V battery, so I drove on city streets for an hour. Everything seemed normal and the red triangle did not return. Hybrid battery was charging normally as well. I went home, parked, checked battery voltage, and then disconnected the battery from the rest of the car by unplugging the two positive harnesses at the battery - I wanted to check for parasitic drain. The battery was at 12.6V that evening, and the next morning, it was 12.4V. That seemed normal to me - to settle a little while resting, after being charged.

I plugged the positive battery harnesses back in, cranked it up, and it drove normally for the day. That was yesterday.

Well today I went to the grocery store, and on trying to leave, the 'no-start' condition came back. Checked voltage and the battery was showing 11.8V. Plugged in the jump starter and the car cranked. Drove home and monitored the inverter voltage while driving - it stayed at 14.0V the whole way. Parked and checked battery voltage again immediately - 12.0V resting, and when I try to put the car into 'Ready' mode, voltage drops to 11.3V!

My sense is that this is a 12V battery issue, but the dealer test is throwing me off.

What might I be missing?

- Ryan