What does the 12V power when car is on?

To be more clear, are you talking about ON or READY mode? In the latter case, the READY light is on.

 

All of the usual accessories are running at 12 volts. (Lights, fans, power windows, engine electronics) It is way shorter to list what is not at 12 volts.

MG1
MG2
the A/C compressor
the HV Batery
and the inverter.

(The spark plugs are also not 12 volt, but they NEVER are in any car)

 

But the "12v" (about 14v) comes from the inverter, not the 12v battery (it is slowly being charged) when your Prius is in "Ready" or "ACC" mode.

JeffD

 

In other words, when running, your Prius powers the 12V battery, not the other way around.

Tom

 

you're right... the answer is nothing. when the car is on all it does it get charged. all 12v items are handled by the 12v inverter once in ready. i find that's the best time to mess with the battery since you won't lose presets and such.

so.. what does the 12v do? when not in ready mode it does everything.. when going into ready mode.. it switches on the relays that let the hybrid system turn on. compared to a conventional car that pulls a lot of wattage (thousands? i think it's less but don't remember) to turn over the engine, a prius uses about 80 or so watts to clip on it's relays. it's not much. i don't remember the exact draw, but i've done test in the past powering up the car with much smaller 12v batteries. i even powered up my car using a cordless drill power pack.. it was a higher voltage but the voltage was low, and in range for the car to use it.

 

It may, however, use the battery to help stabilize the 12V power a bit; for example, if a high-power 12V load (say the headlights) switches off or on quickly, having the battery may help keep the voltage relatively constant. The DC/DC converter may or may not be able to adapt quickly to changes in load.

That said, cars aren't really known for being electrically quiet, soooo....

 

I believe this isn't quite correct...

The "12V" system and everything that runs off it is really powered by the inverter (and the 12V battery is being kept charged) when in "Ready" mode.

In "ACC" mode the inverter is off, and the accessories run off the small 12V battery (except when using the remote A/C on the solar roof model, then the HV battery powers the A/C even though the car is not "Ready"). You should not run accessories for a long time, especially heavy power using ones like seat heaters, in ACC mode.

 

In the spirit of being pedantic, I believe this isn't quite correct...

Where you both refer to "inverter", I think you mean "DC/DC converter". The inverter takes the DC battery input and produces an AC output to the motors. The DC/DC converter takes the high-voltage DC battery input, and produces a low-voltage DC output.