Question about low speed EV mode on hybrids
 

From what I understand, the Honda Insight doesn't have a pure electric mode like the Prius when driven around 25 mph. Is this correct ?

Also something I wonder about with the Prius is just how far that you can drive on pure EV mode.
If I am stuck in 30 miles of bumper to bumper traffic, how many miles of that would be pure EV if the speed never reached over 20 - 25 mph ?

True about the Insight.

Hi Cd,
The Prius has approximately 2 hp-hr battery capacity. If you start your crawl with the battery "full" and discharge down til the engine starts to recharge it you can use about 1.2 hp-hr. The Prius uses about 2 or 3 hp to maintain 25 mph. So the most optimistic estimate is at a constant speed you could go about 15 miles. But if it's stop & go, the accelerations and braking will reduce that considerably. Accessories too. High or low temperatures reduce battery capacity.

-mort

In ev mode you're lucky to go 1 mile. Unfortunately, 15 miles it totally unrealistic.

EV Mode, just over a mile... 2 kilometers tops (from a dead stop), and at a limited top speed. After that, you have to recharge. We tested it during an eco-run.

It's possible with the battery size of the Prius, you could go further, but the system limits it to preserve battery life.

Well this certainly changes my views on the Prius versus a traditional high mileage car.

So after a mile of stop and go traffic, a Prius fires up its engine and pollutes like the rest of us ?

Hmmm. No thanks.

Hi Daox,
I have a Ford Fusion Hybrid. My morning commute includes a stretch of about 4 miles, flat, no lights or signals. 40 MPH speed limit. Most mornings I get to beginning of this stretch with the battery at about 50%. I get up to 40 using the ICE and hit cruise. I make it to the next signal in EV with some battery to spare. So my FFH easily does 4 miles in EV starting with 50% soc.

-mort

The Prius merely exits EV mode and goes back to hybrid mode, meaning it pollutes under hard acceleration and doesn't pollute under gentle acceleration, when coasting, when stopped at a stoplight and when decelerating. Like I said, it seems the short range on EV mode is more to protect the battery than because that's all the charge there is.

If we count cruising while already at speed, the Prius can easily do a number of miles without using gasoline when the battery is topped off. The 2 kilometer limit we tested from a dead stop.

I use EV mode every day my Prius since I have a plugin kit. I've also used it without the plugin kit and I'm saying in normal driving you're lucky to get 1 mile. If I was already up to speed and just coasting along, yeah you can get more. I'm also not sure, but I'd guess the Fusion's pack is larger than the Prius' pack just because its a larger vehicle.

If you're looking at pollution, you aren't going to get much better than a Prius unless you go to an EV.

Hi Daox,
Wow, I thought this guy was doing about average, 5 miles in traffic.

Anyway, I noticed the OP's reply. It wouldn't matter if you could go EV mode for a hundred miles in a hybrid (non plugin). All the electrical energy comes from burning gasoline. And I agree, the Prius is about the lowest emission auto you can buy.

-mort

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.

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.

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. :(

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.

It will, if you get a plugin kit for it and don't need to exceed 34 mph.

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. :)