Prius Prime 12 volt VOLTAGE

There are several threads on this issue. This is normal on the Prime - when you first start up it runs a pretty high voltage (14.7 if I recall) which quickly ramps down to mid 12's. The 12V battery doesn't carry much load - the DC-DC converter is carrying the vehicle loads and only has to put a bit of charge back in the 12V battery to restore it to full charge.

 

Trust me when I say there have been many many discussions about 12v battery fluctuations and what to do about it.

Unfortunately, I don't know of any solid answers to your inverter dilemma.

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If it were me:

I would buy an Odyssey PC680* and run it as a buffer battery, it would go between the OE 12v battery & your inverter. The great thing about Odyssey batteries is they are military grade and can be mounted in any possible position because they're 100% sealed & can Never leak or vent.

I would use at least 8 AWG wire as a bare minimum from the OE 12v to the buffer battery. Also, twist the wire going from the battery to the inverter with multiple twists, this cuts down on RF interference.

www.odysseybattery.com/Specs/ExtremeSeries


Rob43


* Or similar.

 

It’s by design, for energy efficiency. The operating principles are the same as on fourth-generation Prius cars, which I discussed in post #4 and post #18 of a previous thread.

You haven’t mentioned the duration or duty cycle, but I think it’s safe to say that Toyota didn’t design the low-voltage electrical system on the Prius or Prius Prime to supply an added load of this magnitude.

Keep in mind that the maximum output current of the DC-DC converter is 100 A, at 11.0 to 15.0 volts DC, according to New Car Features (more info). Toyota does offer a 1500 W inverter as an option in Japan, but it’s connected to the high-voltage system, usable only when the car is parked, and—most important of all—controlled by the Hybrid Vehicle ECU, as described in my May 2017 posting.

An added battery, as @Rob43 kindly suggests, wouldn’t help if the problem is long-term energy balance. The battery can temporarily provide additional current, but it can’t do that for long, and it must then be recharged. Over a long enough period of time, your inverter and the other electrical loads can’t take energy out of the system at a greater rate than the DC-DC converter is putting energy into it. That’s limited by its design and controlled by Toyota’s software, not easily modified.

 

^ Agreed, this is not a long term solution for hours of daily operation, it is a short term solution for daily use. The buffer battery would help as a short term stabilizer, but then would need to be recharged by the electrical system for the next event.

You certainly can't take more from the system than the system is supplying,.....and get away with it.


Rob43

 

Is the inverter's negative connection made upstream or downstream of the battery state sensor?

In other words, has it been wired to make sure the car is able to measure the added power consumption?