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Old 11-22-2011, 01:59 AM   #11 (permalink)
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It's important to remember that the hybrid battery is meant to assist the engine and not mean as the sole propulsion for the vehicle except to move out of the garage or to a nearby parking spot. The Atkinson cycle engine in most hybrids is very efficient but lacks power. This is where the battery and motors come in to play. They boost performance and drivability.

The HV battery is mainly charged by the engine which is fueled with gasoline so if you are using the HV battery exclusively you are actually less efficient than running one engine power. The laws of thermodynamics are unforgiving. So don't try driving around in EV mode or your mpg will drop.

As for pollution, the OP needs to do more research on how hybrids work. They are not meant to be driven in EV mode for extended periods nor will they pollute as much as non- hybrids in the same class (generally speaking). You simply will not find a more fuel efficient clean burning vehicle in North America than the Prius.

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Old 11-22-2011, 11:12 AM   #12 (permalink)
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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.
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Old 11-22-2011, 11:27 AM   #13 (permalink)
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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.
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Old 11-22-2011, 12:15 PM   #14 (permalink)
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TWith 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.
Not to mention that if you warm up the engine quickly, you'll be getting cabin heat for free.

One of the several reasons that I don't really like the Prius design is the fact that it has a pure EV mode at all. As others have said, it's not really efficient to drive in EV mode, then recharge the battery from the motor. With the Insight + MIMA, virtually all my battery charging comes from braking or going down hills, so it's "free" energy that'd otherwise be wasted as braking heat.
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Old 11-22-2011, 12:21 PM   #15 (permalink)
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Not to mention that if you warm up the engine quickly, you'll be getting cabin heat for free.

One of the several reasons that I don't really like the Prius design is the fact that it has a pure EV mode at all. As others have said, it's not really efficient to drive in EV mode, then recharge the battery from the motor. With the Insight + MIMA, virtually all my battery charging comes from braking or going down hills, so it's "free" energy that'd otherwise be wasted as braking heat.

The Prius used regenerative braking as well but it doesn't supply as much energy as the engine does. The Civic IMA system doesn't either. On my commute I have a 1,200ft. elevation change so my battery charges to full if I choose to let it regen. Normally I just glide for the long downhill section as this is more efficient.

I wish Honda would have set up a better system for keeping the battery cells leveled off. As it sits we have a ton of Civic owners with useless or barely useful batteries because of this. There is a device being built which can fix the situation and it's only about $500. I hope it comes out soon so the Civic guys can regain their lost MPG.
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Old 11-22-2011, 08:58 PM   #16 (permalink)
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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.
I guess its my EV that has to run during the winter, I plan on moving back to about 1.5 miles from work, during the freezing time of year sloshing through snow I think a prius might make it there and back on electricity if I could prevent the engine from starting, ah well.
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Old 11-22-2011, 10:45 PM   #17 (permalink)
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It will, if you get a plugin kit for it and don't need to exceed 34 mph.
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Old 11-23-2011, 04:33 AM   #18 (permalink)
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I guess its my EV that has to run during the winter, I plan on moving back to about 1.5 miles from work, during the freezing time of year sloshing through snow I think a prius might make it there and back on electricity if I could prevent the engine from starting, ah well.
Yeah, the Prius might make part of the trip but it would eventually start the engine to recharge or warm up. Below a certain temperature the vehicle will start no matter what. Like Daox stated, you could buy a plugin kit but they are still expensive or require a lot of tweaking.

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