Charging the 12V Battery??

Nope. When you charge the traction battery, it also charges the 12v. The traction battery also keeps the 12v charged when operational in EV or HV mode.


Unsupervised!

 

Yep. The battery is a little small for extended discharging. Being a lead-acid type (I know it’s an AGM) of battery, they don’t like being left in a discharged state for any length of time. Best to leave them charged at all times.


Unsupervised!

 

can you please post the section in the manual that recommends charging the 12v?

 

When I first started thinking about Prius, I'd notice Prius cabs (as I was walking to my morning train commute) sitting in cold parking lots, steam coming outa the back. I couldn't get my head around it: the world's most efficient car, sitting idling.

Anyway, a 30 grand, air conditioned iPod you sit in? Sure you can do it. As mentioned above, have the car fully on.

Don't mind me, I'm a curmudgeon, I know it, lol.

 

Are you sure? With my Prime off, the 12v battery read 12.4v. While charging, my 12v battery read 12.4v. When the Prime was in READY, the 12v battery read 13.9v. This made me think the Prime did not charge the 12v battery during a charge of the traction battery. The 2012-15 Plug-in was different.

 

interesting, i wonder why they would change it.

 

No car is going to charge an ailing battery that well. It'll keep a battery in good health at status quo, but that's about it I think. A 12 volt battery consistently sitting around 12.4 Volts will need a decent charger to get it up to snuff.

 

my pip shows higher when plugged in. that being said, 12.4 is awful low for a new car.

 

interesting, manual is not very specific about 12v battery charging, here is what I found relevant:


so clearly, 12v battery gets charged while vehicle is on.
Charging 12v battery while the system is plugged in and charging appears to be the case, but the last bullet is vague ...

 

Im working on a project with my Prime, and noticed that the 12-volt battery voltage does not STAY above 13.6 volts while the car is in READY mode. It shows >13.6 for a short while and drops lower even while driving. When in hybrid mode, when the ICE kicks on, sometimes that kicks it back to >13.6, but not always. Sometimes putting in park, sometimes pressing the brake, but none of these are consistent. I think its 100% normal tho, as nothing seems to be wrong. Lights don't dim or brighten. I just think its a software function of the inverter control that cycles different charge voltages into the 12 volt battery while READY. I need to monitor it more closely to see how low it actually drops and how high it actually climbs. The car is new.

 

i think others have reported this observation

 

Huh? Mine is a conventional flooded lead acid battery. It certain is not an absorbed glass mat lead acid battery. Periodically I remove the cell caps to check the level of the electrolyte and add distilled water if needed.

A so-called 12 volt lead acid battery is 100% charged at 12.7 volts. Of course it takes more voltage than that, 13+ volts, to force the charge into the battery. At 12.0 volts the battery is just over 40% charged.

 

with the quarantine, i've been driving my prime maybe once a week, and often on EV only mode. I let it sit with about 50% full gas tank and about 60-70% SOC. Do I need to worry about the 12v battery? Or anything else? I'm so used to driving 100miles+ every weekday that this is very different. Of course I factored the miles driven into the savings of owning a Prius, and the gas prices...but that's another story.

 

If you are driving once a week, I would not worry too much about it. My car is sitting on my driveway most of the time now, but I do drive at least once a week for about 30 miles HV mixed with EV. I have an almost full tank of gas and have been keeping the battery SOC at 35-45%. If you are not driving a longer period and worry about it, plugging in a maintainer may be a good idea. I have one but have not used it yet.

 

^
Put a volt meter on it & see what your exact voltage is.


Rob43

 

@mistermojorizin if your once a week drive is short, say under 10 miles, and this goes on a while, you might have problems. Either a smart charger hook up, or disconnecting the neg cable (if charging not possible) "might" be worthwhile.

Monitoring the voltage will give you some feedback.

 

when you say charging not possible, do you mean charging the traction battery? I can keep it plugged in in my garage, but I'd rather not mess with any other kind of charging.

 

He means the 12v battery.

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Rob43