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Old 11-22-2011, 11:27 AM   #13 (permalink)
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F8L's 2012 Prius - '12 Toyota Prius Three with Solar Roof
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Originally Posted by rmay635703 View Post
The real question is how do you bypass the prius EV mode limitations?

AKA I am told if you do actually charge the HV batpack before leaving the motor runs constantly until the battery is in the 80% and under area wasting energy.

Not sure how we could make the most use of the Prius battery as many of us have relatively short distances to traverse especially in winter that would be best in EV mode.
The engine does not run, in the traditional sense, when trying to dissipate energy. Once the HV battery is over approx. 77% State of Charge (SOC) the motor will spin the engine to act as an air pump and dissipate additional energy. There is no fuel pumped during this situation and although RPM will raise to over 3000 no fuel is used and the car does not accelerate on its own. It still drives like normal just with a bit more noise due to higher RPM. It's a pretty smart system.

Short trips are going to kill your mpg no matter what you do. Driving on the HV battery is not going to help you. You will simply have to recharge the HV battery via gasoline at some point and therefore you take a double hit to mpg. Using gasoline to charge the battery then using that energy to move the car is not very efficient. With very cold temperatures it is best to get your engine warmed up as quickly as possible to reduce the warm-up phase mpg impact which all vehicles have to deal with. Most people use an engine block heater to assist in warm up time and grille blocking techniques. Short trips (first 5 miles) may only get you 25-35mpg but after that the engine warms up and goes into closed loop mode and your MPG goes back to normal (44-55mpg) or more depending on your speed, driving style, conditions etc.. Imagine what you are getting in a conventional car while it's warming up.

Keep in mind that if you deplete the HV battery you will have to recharge is via gasoline and during that time your mpg will be reduced compared to driving with a full battery. The reason is because the engine has to work harder to maintain your desired speed AND recharge the battery while getting no additional HP/TQ from the battery. So your 110-134hp car is now down 76hp because the battery cannot assist. My numbers are a bit off but you get the point.
2012 Prius Three with Solar Roof - Blizzard Pearl w/dark gray interior: Prius Plug-In 15" Wheels | Michelin Energy Saver A/S 195/65/15 tires | TRD Lowering Springs | WeatherTech FloorLiners | Scangauge II | Morimoto/DDM HIDs 5000K | Clazzio Leather Seat Covers | Best Tank: 71.7mpg@702miles | Best Trip: 95.9mpg@233miles
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