12v battery

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Fairly common, might need to upgrade the search skills or read a bit more in the forums.

No.

No, or very unlikely. You could put it on a charger or return it.

Yes. Do you have any OBD2 codes (DTCs) that you can share with us?

Sounds like a P0A93, and you may have a failed inverter coolant pump (or worse), when was it last replaced or inspected?

 

The prius is a HEV (hybrid electric vehicle) and the health of both (all) batteries is paramount for it to function properly.

GOOD LUCK!

 

Or certainly the inverter isn't doing it's job any more.
That device serves the function of an alternator in a conventional vehicle.
When it fails, the battery won't charge.

 

Have you had a chance to inspect or clean the HV battery fan near the 12v battery?

 

The battery isn't being charged. While driving, the car is using power from the battery, which steadily drains, until it can no longer power the car.

The DC/DC converter is what charges the battery. It clearly works sometimes (you would never see 14.2 or 14.9 without the converter online), but it is turning itself off for some reason, at which point you get dash lights and a beep to announce that it is a known problem.

It would be good to post all of the trouble codes retrieved when that happens; they will explain why it is shutting off.

 

I'm having the same temp measurements as you, and I swapped out a battery pack already and my 12V was warrantied by Toyota. If I were to hazard a guess, it's because of the ambient temp increase. Running the AC full blast and maxing out the blower fan helps a bit.

After looking and feeling the airflow setup in our gen Prius, then comparing it to other iterations of the car (3rd gen had blower directly on pack), I'm thinking there was a notable heat issue that was never dealt with. I planned to do some schematic work on adding a second blower to pull the air out of the pack, and to shroud it a bit better from when it "exits" the vehicle.

I say "exit" because if you watch and ready it in operation, it's using that little plastic interface and grill area to evacuate the heat, the only problem is that there is no exit shroud (at least mine didn't have one). I actually measured the air movement and since the top portion was not covered, it was dumping heat back into the compartment, thus raising the temp. Can't be good for the 12V, and will raise the temp of the exhaust from the fan as well.

I have a temp gun that I've been using to monitor the intake/exhaust for the battery cooling system. I may be overthinking it, yet I look at newer gens with newer blower/exhaust fan designs so maybe there's something to it. I did notice that my battery pack likes it at 100-115F for operation. Anything else and it's too warm.