Just so I understand 12v charging

No but people who don't know how to interpret the readings DO.
Maybe not intentionally.

 

Perfect.
Thank you.

 

Thank you for the additional explanation.
That's what I was getting at.

 

I would answer no for Prime and yes for Plugin (2012-2015). When I put a voltmeter on my Prime’s 12 volt battery, the reading when everything was off was the same as when it was charging the traction battery, leading me to believe the Prime did not charge the 12 volt while charging the traction battery. When I put the Prime in READY, the voltage on the 12 volt went up so I believe it was charging.

My Plugin was different, as the voltage on the 12 volt went up during charging of the traction battery.

I suppose it is possible the Prime charges the 12 volt during traction charging IF the 12 volt is at a low state of charge, but I have not seen this.

 

see post #9

 

I think on the prime it does because the main battery is heated or cooled by the 12V battery during the Charge cycle.

 

there wouldn't be enough power for that. it is heated or cooled by the hybrid battery itself, delaying charging.

 

You could turn the headlights on for a few minutes prior to doing the charging test.

 

There is a DC to DC transformer that steps down the voltage from the traction battery for powering 12V accessories. So something being 12V doesn't mean powered by the starter battery.

 

Just editorial: which battery do you mean by "starter battery"?

 

In my Prius Prime 2018 sold in Canada, the manual says, and while I can't find the spot here, I am pretty sure it says the heating is done by the 12v, and that is why if it is plugged in for more than 3 days, the heater auto stops. But I am probably wrong lol.

■ Hybrid battery (traction battery) warming control (Alaska and Canada only) This control operates after the charging cable remains connected to the vehicle for 3 days and “Traction Battery Heater” automatically stops. It automatically insulates the hybrid battery (traction battery) in extremely low temperatures. ● This control stops 31 days after the charging cable is connected, even if it is still connected to the vehicle. ● When this control operates, timer charging settings are ignored and charging starts immediately.


●“Traction Battery Cooler” uses the power of the hybrid battery (traction battery) and external power source. • While “Traction Battery Cooler” is operating, the amount of the remaining charge of the hybrid battery (traction battery) increases and decreases in a certain range, and does not increase as in normal charging.

 

There is no such thing as a DC to DC transformer.
And there is no "starter battery" in a Prius.
It is the accessory battery........and the accessories and computers are sometimes powered by the battery and sometimes by the inverter.

 

agreed, i'm not exactly sure what they are saying there about the 'heating' and 'insulating'. would love to know the details.

 

Your post was oh so helpful

I used the wrong specific term for a specific type of power converter. Electric power conversion - Wikipedia
Is providing a correction too heavy a lift for you? (It is a converter, not transformer, for those interested.)

People commonly use starter when referring to a car's 12 volt regardless of whether it actually turns a starter motor, or just boot up the computers. How many posts have you corrected for using charger when the person meant EVSE today?

 

Good.
Yours certainly was not.
Either of them.

 

There is no need to charge the 12v battery while charging the traction battery just because the fans are running. If the 12v battery is up to voltage the charging system and traction battery will deliver power to the fans while the battery just floats on the line.

 

That's true but the REST of the story is:
The 12 V battery is almost NEVER completely "up to voltage" so any time the charging system is active some charging of the battery is likely to be taking place.

 

agreed, it's keeping the battery from discharging, just not enough to register on your typical volt meter.

 

Interesting find WeberAuto on Youtube:

Apparently the charger assembly on the Prius Prime tops off the 12v battery when plugged in.

(timestamp 20:18)

 

Yes, but not very effectively. It only maintains at ~12.7v most of the time, and occasionally tops off at ~13.5v. And this only happens while the traction battery is actively being charged. Once the traction battery charging is completed, keeping the charging cord plugged in will not maintain the 12v battery but rather drain it faster.

See this thread for more information:
Hopefully, ultimate 12v battery charging system discussion on PP | PriusChat