Is hypermiling killing the battery?

Would love to see a hybrid like the Tesla but make the battery say 1/2 the present size. Since the electric motor does all the propulsion you just need a very small yet efficient gas motor that only runs to recharge the battery say when it has 1/3 charge left and stops charging it say around 80%. Under normal driving conditions I wonder how often that ICE would have to kick in and how long/how much fuel it would take to recharge the battery? Figuring that into the equation I wonder what the mpg would be for such a system.

 

Would love to see a hybrid like the Tesla but make the battery say 1/2 the present size. Since the electric motor does all the propulsion you just need a very small yet efficient gas motor that only runs to recharge the battery say when it has 1/3 charge left and stops charging it say around 80%. Under normal driving conditions I wonder how often that ICE would have to kick in and how long/how much fuel it would take to recharge the battery? Figuring that into the equation I wonder what the mpg would be for such a system.

 

Trace the path of the energy! All that energy isn't equal, nor equally efficient. Putting 10% of the energy into the battery, is not the same as putting 50% of the energy into the battery, which is not the same as putting 100% of the energy into the battery. Do the actual math, assign an efficiency to each of the energy paths, and see if you can make it work out as you claim.

The Volt does (almost*) exactly that. You will note that its efficiency is less than a Prius if you discount electricity from plugging in.

* - The Volt couldn't get that to work, so needed another path where the ICE engine is driving the wheels.

 

ICE engines run around 30-40% efficient.
Gas contains about 32 kWh of energy per gallon (E-10).
A Tesla uses about 38 kWh per 100 miles.
The lowest level battery is 40 kWh.
I doubt you could add a generator and gas tank for the weight of 1/2 the battery pack.
The size of an ICE generator is related to output, so the smaller the engine, the greater its on-time percentage.

 

I disagree here. When cruising with the ICE, the majority of the propulsion power is going through the direct mechanical path through the HSD. Only a minority of the power takes the lossier path through MG1 / rectifiers / battery / Inverters / MG2. The torque split is 72% mechanical and 28% electrical, but differing RPMs of the spinning components makes the power split different and variable.

This is why cruising on the ICE is more efficient that EV at medium and higher speeds. EV is better at low speeds where the extra electrical path losses are less than the overhead needed to keep the ICE spinning fulltime. But Pulse & Glide can handily beat either.

This is also why the Honda Civic Hybrid can outperform the GenII Prius under certain highway conditions.

It sounds like you are describing the Chevy Volt, with slightly modified software, and without using the plug-in.

 

Corwin is correct. If you are using gasoline to make electricity to then run a motor then you are on the wrong end of an efficiency loss chain. The reason the EV's look so good is that they use energy from a utility, not gasoline. The plug-ins start with a battery full of cheaper energy which gives them a big advantage in mpg's for shorter trips. After they use the house energy, they are a hybrid just like the non-plugins.

 

The point our "experts" overlook is a hybrid captures energy that would be lost in a normal car. When you are in EV mode you are simply cashing in on that energy.

 

That is not being overlooked. Rather, many others are overestimating how much energy is typically harvested this way.

Normally, it isn't enough for lots of EV cruising.

 

I don't think the "experts" are overlooking that at all. The only way to look at hypermiling is to look at the entire system and consider all of the energy flows in the car the whole time, from gas pump to gas pump.

Yes, the hybrid is an energy recovery system a normal car doesn't have and yes that makes hypermiling a Prius a completely different thing to fuel efficient driving in a normal car.

The bottom line is that it's not "free energy"... it's just mitigation of energy loss... and whatever it is, hypermiling is all about how to best use all of the energy you have available to you.

 

My commute is less than 8 mi. and only for a short stretch, is over 35 or 40mph. I have one fairly long and severe "inverted" hill. More like going from flat to down into a valley then back up. I stay under the midway point on the ECO display area and am in EV over half the commute. I use that hill, normal coasting and stopping at stop signs to regen and have made all the way back home with the ICE never starting. I have been in stop and go traffic for miles before on EV only. I figure the car is doing what it's supposed to do. I'm getting the feeling I should be forcing the ICE on from reading all the comments.

 

completely unnecessary. comments are from ignorance and fear. spell that fud.

 

Letting the car do what it's supposed to do, is more than half the battle.

The rest is knowing what the car is supposed to do, and using your knowledge that it doesn't have, to fine tune things.

When you do your commute without the ICE coming on, the battery is in a lower charge state then before the trip. That charge can only come from running the ICE. So you haven't prevented it, merely postponed it. Which can be fine. You want the ICE to come on only at the most advantageous times. Perhaps there is no such time in your commute, and your charging should be done when you go shopping. Hard to judge from here.

 

Every one of these arguments stem from people not specifying whether they are using (much or any) power when they're in EV mode. We see the same argument over and over, with the same miscommunication.

To sum up what people should take from this:

#1- No, you should not draw serious power (bringing the ECO score power bar up to just below the first line, for example) on your battery over distance to attempt to get better mpg. The ICE will simply have to recharge the battery, and that is an extra energy transfer that is inefficient. It's not good for the battery to drain it down as much as possible, either.

#2- However, GLIDING- shutting the engine off (going into EV mode) and using no EV POWER, or at most, very little, just to maintain speed below 43 mph- is extremely efficient and is where one gets the huge mpg in the Prius. THE EFFICIENCY IS IN SHUTTING THE ENGINE OFF WHILE STILL GAINING DISTANCE, NOT USING ELECTRIC POWER TO PROPEL THE CAR INSTEAD. The battery will still drain a little while gliding, but the energy lost will be more than made up for in the distance gained without the engine on.

 

Ok, just left my nephews house from giving him some tips on tiling his kitchen. He's an EE with an company that is currently working on converting plastics to liquid fuel as sort of a side project. Their current delima is same as ours. It's taking more energy to convert it than comes out of the end product. His take on it is this. You can run the battery and save on fuel or run on both. "Gliding" buys us time and distance between charge and discharge. If we didn't have a battery it would be a waste not to use it when possible or it's just a novelty. No matter which energy source we use, it's still going to have to be replenished.

He drive it back from the "Home" store and threw this in at the end. "I see no one is taking into account the energy you expend by driving it the way we are in order to mitigate the losses.

 

Think of it this way: When you are in EV mode you are still burning gasoline, but less efficiently. You are converting the engine's mechanical movement-to-electrical energy-to-chemical energy (in the battery) then back to electrical energy & a final conversion to mechanical (to spin the wheels). So 4 conversions which induce losses.

It is FAR more efficient to just draw the energy directly from the engine's mechanical movement to the wheels w/o any conversions.

The only time EV mode is more efficient is when the engine is idling or near-idling, and burning gasoline but not producing much motive force (running inefficiently). So basically any speed below ~20.

IMHO.

 

I like simplified explanations......but I think that is a little TOO simple.

If your first statement were 100% true, then what's the point of having a hybrid at all ??

And.....is it really "EV mode" if the engine is running ? I don't think so.

 

I wonder the same thing in my Honda where I achieve high MPG by Not using the battery (except to have faster 0-40 takeoffs). So basically I use the hybridization for power, not economy.

The Toyota's EV mode is also good for under 20 driving when the engine is running inefficiently.

 

Totally agree. After 4 months of ownership, the constant "pulse and glide" is just too spastic a way to drive a car and probably the reason I don't get the disrespect others report. You have 2 energy sources. Whichever one used is eventually going to have to be refilled. I run on EV as much as possible, coast and use my brakes to regen. I've easily gone 10 or 15 miles before completely on EV under 40mph and finished up with 3-5 pips on the battery and 99.9mpg showing on the display. It's like bragging about how long the batteries last your cell phone simply because you keep it plugged into the wall.

 

My nephew who is an EE says the same thing. Being a Hybrid would simply be academic.