Most decent way to run your 115V essentials out of Prius Prime

In Liftbacks, it is worse than that -- when in N, it can't even start the engine. So this inverter arrangement could simply keep draining the traction battery so low that it is unable to start the engine even when the operator later shifts to P.

This why a Liftback driver must not coast down steep hills in N with the engine not spinning. Above a certain speed, the engine must be spinning to prevent overspeed damage to MG1, but the engine can't be started up in N, as all the MG fields are disabled.

And this MG-disabling N mode is a safety feature for other reasons, so I don't expect it to go away.

It would be a bit of a bummer if there is no override of that auto-shutdown. Earlier LIftbacks can operate continuously as backup power sources, for days, no driving breaks required. Though with much smaller traction batteries, the engine must cycle On and Off much more frequently.

 

Well, I am currently testing my PRIME to see if such auto-shutdown feature exist. My 2020 PRIME LE has been parked for over two weeks now and I have not had chance to use the traction battery, but the 12v battery is continuing to drain. It would be a good opportunity to use the traction battery to charge-up the 12v battery without driving. So far, 2 hours, the car has not shut down. It is just sitting PARK enabled in READY. No A/C and no lights or radio. With minimal load on 12v battery the traction battery is nicely charging the 12v battery at 14.1v for the last 2 hours.

I am not sure why the OP's PRIME is shutting off after 30-40min on P in READY. It maybe due to heavy load on 12v from the inverter attached, but I honestly don't know.

 

Did something here change with the Prime's 2020 refresh? I seem to be vaguely remembering something related to this auto-shutdown, but not with enough detail to track it down.

Krzysiek has the original 2017, while Salamander has the refreshed 2020, so this might account for some differences.

 

Again, you're a few minutes ahead of me. LOL!
Do 2020 models have auto engine shut-off? | PriusChat

(Google search is much better than the forum software's search. )

 

While that thread is about auto engine shut-off, there is a relevant comment there for auto hybrid system shut off with a quote presumably from the manual. But I can't find this in either 2017 or 2020 PRIME manuals. So I don't know what vehicle this "Automatic hybrid system shut off feature" applies. I feeling is it only applies to 2020 Gen4 Prius AWDe.


Edit: OK, I downloaded 2019 and 2020 Prius owner's manuals. I found above quote ONLY in 2020 Prius owner's manual (this include AWDe, but applies to all models of non-plug-in Prius). There is no mentioning of "Automatic hybrid system shut off feature" in 2017 PRIME, 2020 PRIME and 2019 Prius owner's manual. So, this seems to be a new feature added to 2020 Prius models, but not to PRIME.

This makes so bizarre that OP's 2017 PRIME is somehow having this feature, but not my 2020 PRIME.

 

That might be the difference. Yes, PRIME will detect fob not being inside of the car and warning will come on the MID. Maybe without fob, it forces the undocumented automatic hybrid system shut off. I had my fob inside for my testing. I can try removing the fob and see what happens.

 

In a Gen3 Liftback, the power steering warn is an indirect indication that the gas tank has run dry, ICE has stopped, and the traction battery is getting too low. The Prime may have other or additional causes for this warning.
[WARNING] Running out of gas (Gen III) | PriusChat

I suggest that you be very careful about "N" gear, be damn sure that the electric range is never allowed to drop to 0 miles. Such cases are where "P" ought to be a better and safer mode than "N".

 

I have a feeling there is something going on with your car. Is your 12v battery healthy? After ~4 hours on P and Ready with a fob inside, I removed my fob. I get the warning on MID "Key not Detected Check Key Location". The car beeps when I exit from the driverside, but that's it. The car was on P and READY for another 3.5 hours without any other warning or the car shutting itself off. After 7.5 hours on P and READY, I turned it off. The traction SoC was reduced from 98% to 74%. But my 12v battery was charged up from 12.62v to 12.97v. The graph shows the 12v battery voltage monitored by the battery monitor. During the entire 7.5 hours, the DC-DC inverter was charging the 12v battery at ~14v, it never stopped at any time.

 

I now think there is definitely something wrong with your car. PRIME certainly charge 12v on P and READY. On the contrary, I have shown charging the traction battery by connecting to the EVSE does not charge the 12v battery. So, if your 12v battery was depleted while you had your car in P and READY, the first thing you have to do is to check your 12v battery and charge it with an external charger. Still, I think your 12v battery is not healthy. That may explain bizarre warnings and strange behavior you are seeing on your PRIME. If I were you I would not use the inverter until I know 12v battery is in good condition, regardless of shift position. But I would never try using any inverter on the "N" position in my car.

 

In other Prius models and generations, the 12V is charged all the time the car is "READY", regardless of gear mode. But while the ICE can charge the traction battery in "P" and all moving gears, it cannot charge that big battery when in "N", so there is a risk of running it very low.

It will eventually shut off the hybrid system to protect the traction battery from complete depletion, saving it from inverters tied to the 12V bus, but then the 12V gets drained. And the car will not protect itself from inverters tied directly to the traction battery, as certain users do (with different equipment) for higher power capacity.

I'm trying to follow what differences the Prime has from other models, and trying to think of how something might be odd about your setup.

 

Something weird is going on for sure. I have a volt meter plugged into the 12V outlet between the seats. When I start the car, it briefly displays a 12.X volt reading (maybe for a half second) until the DC/DC converter wakes up Then it jumps to 14.x. Car is still in park at this point and is obviously charging the 12V. As the charge level in the 12V increases, the displayed voltage will drop to a maintenance voltage just north or south of 13.0V. It's no longer charging the 12V because the 12V is already charged; it's just maintaining that voltage against the load placed on it by the car's systems. (Well, you could say it's letting it discharge a tiny bit and then very lightly charging it back up.)

It treats the 12V like that in D, B, R, P, and N. However, as repeatedly pointed out here & in the manual, the ICE does not charge the traction battery in N because that would require spinning one of the motor/generators to generate charge current and that would make the car move, which wouldn't be very Neutral.

So, looking at the voltage of the 12V won't be a reliable indication of whether the car is charging anything because it might not need charging at the moment. But looking at the gear position is a 100% reliable indication of whether the car will charge the traction battery if the traction battery needs to be charged. It's easy to verify by using up the EV range, leaving it in Neutral, and watching the energy flow monitor on either display. You'll see it leaving the traction battery and not flowing from the ICE to the battery.

 

Better get that thing to a dealer then. Here's my aux battery voltage with the car in Park:

This is to be expected. UNTIL the point where the EV range is gone and the engine starts. Then you will have issues because it won't charge the traction battery. Try it, but watch it carefully or it could get very expensive. Note: this is completely unrelated to the charging of the 12V aux battery.