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I had read that you can run a Prius II AC on HV (elect) only if you set it to the lowest setting.

Isn't the Prius II AC based on controlling a certian temperature?

How do you set it to the lowest setting to keep the ICE from firing up?

I don't yet own a Prius but was still curious.
 

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2004-? Prius has the AC compressor run off of the HV battery. If the HV battery gets too low, the gasoline engine will come on to recharge the HV battery. the fans are run off of the 12v accessory battery (which is charged off of the HV battery). Heat is still the conventional way - "waste" heat from the gasoline engine, so it is possible that the engine will run just to provide you with more heat. You cannot force the gasoline engine from not turning on for recharging or heat reasons, unless you only keep your Prius in the IG-ON mode or turn off the Prius.
 

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But then, Ig-On won't get the compressor going either.
You can keep the engine from fireing up in Neutral. Eventually though, the HV battery will drain to an uacceptable level, and the car will shut off or go to Ig-On to protect the battery. Not sure which as I've never actually done this
 

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2004- Prii employ electric air conditioning; true. This system is high voltage which means it runs off the HV circuit on the vehicle, which includes the battery, buck/boost converter and motor generators.

The auto climate control system is just like a home thermostat. You set the temp you want and the vehicle works toward keeping the cabin at that set point. It does this by managing outside air, inside air, heater core and air conditioning compressor. This fall I have moved my A/C down to a set point of 70 degrees. This summer I had it at about 74 degrees. This means that in the morning the vehicle is heating the cabin and in the afternoon when driving home it is cooling the cabin.

The efficiency of the a/c system is a combination of many factors. Automated use of recirculated air. Recirculation of air in the footwell, but not the air sent to dash vents. Combining outside and inside air in ways that maintain more inside temperature without making the cabin stale, and so forth. But the compressor also is variable speed, thus allowing the auto climate system to run the compressor at a more efficient lower speed if the cabin is close to the set point or the vehicle is working to maintain the set point.

Because the air conditioning compressor runs off electricity, it will run at stop lights or when idle when the ICE is not running. The battery is like a buffer. Since the car generates a good deal of electricity through regenerative braking, and since at cruise the engine is usually turning MG1 and generating power, the HV battery is not heavily affected by the use of A/C Most people say they only loose a couple miles to the gallon when it is very hot out and they use the A/C the most.

You really don't have much control over ICE startup. If the state of charge on the battery is such that the system wants to top off the battery the ICE will run. But the ICE will also run when it would usually not during the winter to provide heat to the cabin.
 

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DanMan32 said:
But then, Ig-On won't get the compressor going either.
You can keep the engine from fireing up in Neutral. Eventually though, the HV battery will drain to an uacceptable level, and the car will shut off or go to Ig-On to protect the battery. Not sure which as I've never actually done this
I don't use IG-ON often enough to notice that. Other than the fan going I don't know when the compressor is on...

But in Neutral, you can force the engine to come on - floor the accelerator pedal. Makes lots of noise, but that's about it.
 

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I'll have to try that. ICE should not be able to turn on in N as the MGs are supposed to be disabled. The car needs MG1 to start ICE, with MG2, parking pawl or brakes holding the car (and thus the ring gear) in place. But if ICE is already running, even at low RPMs to be nearly unpercevable, then hitting the accelerator will make it rev faster.
 
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