2011 Prius shuts down when brake pedal pressed to start, but...

What’s “it”?

Clarify “over the range”?

 

What do you mean the battery measures "over the range" when the car is turned off?

the 14.4 when READY is no surprise; you're not measuring the battery then, you're measuring the car's DC/DC converter output.

I suspect that when you step on the brake, the brake pressure pump is running and pulling the battery voltage down too low for the dash to light up, and you get the lights back when the pump shuts off.

The pump normally sounds like a little rattlesnake or joy buzzer and just runs a few seconds. But at much reduced voltage, it sounds more like a dying wind-up toy and takes a lot longer to shut off.

First guess is your 12 volt battery is ready for replacement, and if you're convinced it's a-ok, second guess is a lousy electrical connection, maybe at the battery or the nearby ground point.

 

The 14.4 volts is from the inverter, charging the battery.
Turn the car off, then measure the battery.
How old is the 12v battery? If it's 5 years or older, it's likely do to be replaced.
How much driving do you do? Around town? Highway? If you're taking short trips,
it's likely the 12v battery is not, and has not been getting a long enough charge, and has
slowly gotten weaker and weaker.
You could try a 4 amp or less charger on the battery for 12 hours, that should give it a
full charge. Then measure it. It should be up around 12.7 or so. If after charging it's only
around 12.3 or so, likely it's life has been used up.

 

Yeah your battery's got 12 and 14 volts respectively. It just has no AH behind that voltage Time for a 12 volt more than likely

 

my battery has been over the range for years. what's not to like?

 

♫Home over the range
where the vultures and bald eagles prey ♫

 

I don't believe there is a "low battery" icon for the 12v battery.

Don't forget to charge the new battery for 6-8 hours at 5 amps or less....
The dealership or parts stores do not charge them when they get them.
Because you want to start with a fully charged 12v battery.

I didn't suspect the 12V battery, which is 5-6 years old, because the low battery icon didn't light up.[/QUOTE]

 

That's good to hear!
There is NO drain on the disconnected battery, that's why it's reading high.
Put a brake like bulb across the terminals, or a head lamp bulb and it will go down....