About those hybrids...

[Bowser]

This morning's commute to work: 92.1 mpg.

I'll probably surpass 90 mpg only a few times this summer, but getting in the 80s is pretty standard this time of year for me.

It is possible only on trips where I do not, or at least only rarely, have to apply the brake pedal. The idea that hybrids get their best mileage in the city as a result of regenerative brakes is absolutely false as a generalization. It depends on the model's technology. Like the Toyota Prius. I have the Honda Insight which does decidedly better on country road or highway driving than stop & go. Regenerative braking gets back some of the lost power in the Insight, but not all of it.

After three years, my overall average is 63 mpg.

You have to choose the right hybrid for your driving situation, and you have to relearn how to drive. There are internet discussion groups which help with that.

 

[ceptimus]

The problem with regenerative braking is that presently available batteries are unable to absorb energy that fast.

Applying the brakes only moderately hard can easily generate 60KW or more of power. Try to dump that into the batteries and the batteries will fry.

 

[Ladewig]

I have finally met someone I am jealous of. I get closer to 65 mpg on the highway, but that is the result of my going 65 mph. If I drop down to 55mph and am very careful, I can get it up to 80 mpg. Another drop in my fuel efficiency is that when leaving toll booths, I test my 0-60 accelleration time (9-10 seconds).

My only real complaint is the battery's losing charge during a significant temperature change. Although the charge often returns within a half-hour.

 

[Bowser]

"Another drop in my fuel efficiency is that when leaving toll booths, I test my 0-60 accelleration time (9-10 seconds)."

hehe. The Insight has done very well at the Lebanon, New York drag strip, so acceleration doesn't seem to be a problem. It still has plenty of pep.

 

[Walter Wayne]

Accelerated hard dropping fuel efficiency? When I was looking at the various insight websites, I was under the impression the best fuel economy is when one accelerates hard (so you use the battery) and brake slowly (so only regenerative braking is used).

If you drive like a little old lady the insight doesn't use the electric engine much, and one just has a gas car (although a fairly efficient one).

Walt

 

[Bowser]

Walt, it is true that you do want to be using the alternate battery, and if it is always fully charged it means you are probably missing out.

On starting up the recommendation is to go from 1st to 2nd then straight to your last gear, which might be 5th. That suggests fairly hard acceleration, although I have never really come to a conclusion about how hard (I assume the discussion forums may have reached a consensus about this by now).

Regenerative braking only works if you are in gear, so you don't want to go to neutral any sooner than necessary.

I can activate autostop (if it didn't come on by itself) by fully depressing the clutch pedal at a stop, although not until the engine is warmed up.

There were improvements made to the engine, so it runs better than the average 3-cylinder. Your comment, I believe, is geared more towards the Prius, or at least the model from a couple years ago.

Lots of little things that add up, but you need to be aware of them.

 

[garys_2k]

All this depends on the energy strategy the engineers programmed into the vehicle's powertrain controller. Does it prioritize battery state of charge, minimize fuel use, thermal control? Most likely all of these under different circumstances.

 

[Ladewig]

Accelerated hard dropping fuel efficiency?

The only way one is going to get from 0-60 in ten seconds is if the three-cylinder engine and the electric motor are both putting out a bunch of power. The instantaneous mileage during that burst is very, very low (according to my instantaneous mileagometer in the dash).

 

[Walter Wayne]

The only way one is going to get from 0-60 in ten seconds is if the three-cylinder engine and the electric motor are both putting out a bunch of power. The instantaneous mileage during that burst is very, very low (according to my instantaneous mileagometer in the dash).

But what about averaged over distance.

Compare getting slightly lower than average milage acceralting to 55 over a long distance, to getting really bad mileage accelerating hard to 55 over a short distance and then cruising (good mileage) the rest of the distance.

Walt

 

[Walter Wayne]

Bowser, I am not sure where you disagree with my post. We both seem to agree accelerating hard good, and the other things you mentioned seem similar to when I was looking at the Insight quite a while ago.

Walt

 

[Bowser]

Walt, we probably agree. I just never reached a conclusion about how hard was the most efficient.

 

[Ranb]

............I was under the impression the best fuel economy is when one accelerates hard (so you use the battery) and brake slowly (so only regenerative braking is used).

Walt

Hard acceleration requires that the battery be charged while the engine is running to replace the charge lost will speeding up. No free lunch here. Without the battery, the car is just a very low powered and efficient little toy.

Ranb

 

[Walter Wayne]

Hard acceleration requires that the battery be charged while the engine is running to replace the charge lost will speeding up. No free lunch here. Without the battery, the car is just a very low powered and efficient little toy.

Ranb

Braking in gear charges the battery by simply changing the motor to a generator. So the cars kinetic energy charges the battery. So no it is not a free lunch, but in the standard car braking is a pure loss of energy. This is part of what makes the system more efficient, getting back some of the energy you put in.

The caveat is that hard braking reduces kinetic energy faster than it can be stuffed into the battery as chemical energy, so the best M.O. is to reduce speed slowly.

If one accelerates without use of the electric motor, then braking doesn't build up charge (the battery is full) and you waste all that kinetic energy you built up accelerating. If one accelerates hard enough that the battery charge is reduced, there is space for it to be charged with regenerative braking and you can transform some of the kinetic energy you built up back into usable energy.

Walt

 

[Ladewig]

If one accelerates hard enough that the battery charge is reduced, there is space for it to be charged with regenerative braking and you can transform some of the kinetic energy you built up back into usable energy.

If one accelerates slowly enough, one can use the gasoline engine's excess power to recharge the battery. This direct engine to battery transfer also occurs while maintaining a steady speed on a highway (barring usual factors such as headwinds, excessive speeds, poor pavement conditions).

 

[Bowser]

This morning's commute: 93.5 mpg.

 

[diddidit]

If one accelerates slowly enough, one can use the gasoline engine's excess power to recharge the battery. This direct engine to battery transfer also occurs while maintaining a steady speed on a highway (barring usual factors such as headwinds, excessive speeds, poor pavement conditions).

I don't believe the Honda hybrids (Insight and Civic) work that way - they cannot use engine power to recharge, and rely only on regenerative braking. I suppose they could, but that would negate some of the efficiency gain as with a full battery it would be impossible to recapture any kinetic energy when braking.

The Toyota system, used in the Prius and the Ford Escape Hybrid, can do both. It is a much more complex system than the Honda - the Toyota system "Hybrid Synergy Drive" or something like that) can operate on battery power alone or battery+gas, depending on conditions.

did

 

[bignickel]

I don't believe the Honda hybrids (Insight and Civic) work that way - they cannot use engine power to recharge, and rely only on regenerative braking. I suppose they could, but that would negate some of the efficiency gain as with a full battery it would be impossible to recapture any kinetic energy when braking.

If you were correct, then I would be in deep trouble on a very hot or very cold day, when my Insight's battery has dropped down to practically nothing.

As it stands, my car recharges just fine on the highway - sans braking.

10 minutes of highway driving, and my battery is almost to half capacity.