Is hypermiling killing the battery?

Completely disagree. The engine would be more efficient if it didn't have the drag of a battery generator (just as it operates more efficiently without the drag of belt-driven accessories/pumps/AC). It isn't obvious in a Prius, which hides what's going on, but in my Honda hybrid the generator acts like a brake when it's turned on & forces me to press harder on the pedal. That burns more gas.

Also: Mechanical (engine)-to-electrical-to-chemical-to-electrical-to-mechanical (motor) is clearly introducing conversion losses.

BTW the more you use a battery, the faster it will wear out (to answer the original subject's question).

 

Well you can disagree all you want but IF car makers could make a car that gets 50+ MPG (or even 40+) without all of the hybrid complications, don't you think that they all would be DOING THAT ???

The problem IS that you are only looking at one factor; there are several others that are significant.

One of the main points in the design of a "real" hybrid (which I'm not personally sure the Hondas ARE) is to run the engine whenever it does run at it's maximum efficiency, or very near it, and if all the energy produced isn't needed for propulsion, store the extra in the battery.
And then later, turn the engine off completely and use that stored energy.

This results on overall improvements in efficiency, as opposed to using a gas engine only and running it through most of it's time used in grossly INefficient speeds and modes.

 

That is a good guess of how a hybrid like a Prius works, but at least in the G2 Prius where adequate studies have been done, it is more wrong than right. Battery SOC is the major input in how the control logic decides whether and how much power the battery should charge or discharge.

The whys and hows of improving average ICE efficiency are myriad in a Prius. Below I list a few in somewhat ordered list of importance:

1. Downsized, Atkinson Engine. The traction battery supplies (when SOC available) extra power for high demand situations
2. ICE off when coasting below 41 - 45 mph (varies by model, saves about 1 - 2 kW)
3. ICE off at stop (when heater off and Cat warm).

Graham Davies wrote a very approachable and for my money, best monograph on the inner workings of the Prius. I cannot count the number of times I have read it, and I figure I understand a good half so far Highly, highly recommended.

 

Take a look at my signature & tell me the Honda is "not" a real hybrid. It seems to be doing just fine with the MPGs. "You cannae change the laws of physics" as a certain Scottish engineer might say. Conversions from one energy form to another create losses, and there's no way to avoid that limitation imposed by the universe. And yes there are nonhybrids that get over 50mpg. They are confined to Europe and Japan, but they definitely exist.

In the US we had a car called the Honda Insight with 1.0 liter engine, and some of the owners are still driving them even with the hybrid battery disabled. They report getting 60-70 mpg from their nonhybrid cars.

I want to repeat: I have said several times EV mode makes sense below about 20 miles/hour. That's one of those rare instances when using the gasoline indirectly (via battery) is more efficient than using gasoline directly (engine).

 

Better to P&G if traffic allows.

 

If you are braking often and for long stretches, when comvient, and coasting instead of gliding down hills, the ICE isn't having to come on to charge. I got 80.1mph on the way home today. Other than the quick ICE on then off in about 20 seconds at start up and the 2 slight grades I had to climb, I was running in EV for the last 5 miles. See a light up ahead, brake long and slow and get a pip. Go a little over the limit, coast down the hill and use EV and my momentum back up and it's a wash. Since the charge will not go below about 40% or above about 80%, I hardly think it's even possible to stress the battery. Maybe I'm just not of the current paradigm on this thing but doing this has increased my mpg by a consistant 4 without the Tourette's-like, speed up only to slow down and piss everyone off behind you, pulse and glide.

 

"Go a little over the limit, coast down the hill and use EV and my momentum back up and it's a wash."

- This is a violation of conservation of energy (achieving perpetual motion without losses). BTW how fast do you drive when you go home? It sounds like a rather slow pace, where EV would actually be better than running an engine.

 

Unfortunately, numbers in a signature do not mean much. The two things that contribute about 2/3's of the Prius' efficiency are the regeneration systems and the Synergy firmware. If you are not using pulse and glide, then you are not getting the best mileage possible. This means being in EV mode at speeds considerably above 20mph. Minimizing energy losses, whether from conversion or from tire friction is what we are all trying to do.

 

The computer does the EV mode @ 40-45 miles/hour without me even trying. The battery gets near-full, the engine turns off, and the computer cruises along in electric. And yeah I know pulse-and-glide is recommended for Priuses (and Honda hybrids too). Many hybrid drivers do it, but I just don't bother. My attention is on the MP3 book coming out my speakers.

On my first hybrid (insight) I maximized lean-burn as much as possible (that's a 1/25th fuel-to-air ratio instead of the standard 1/14th).

However it was a LOT of work to be constantly staring at the Instant MPG gauge and hold it near or above 100 mpg. And for what reason? To save a few pennies (about 50 cents/day)? I'd rather skip the afternoon snack. After I got rid of the insight I decided "no more". Now I just set my CC on my Civic and Prius to 40-45 miles/hour and try to enjoy my audiobook.

 

That is P&G, on hills.

 

I'm not actually going into glide. I'm totally letting off the accelerator to get a trickle is what I meant to say. Then keeping below the center line on the display so EV is always lit to keep up my speed. Maybe I am following informed opinion and don't even know it. I almost never hit the 2 purple pips when doing this. Maybe I'm just lucky with the terraine of my route, too. My more severe uphill route to work is during rush hour so going up the big hill is at a snails pace for about a mile with no ICE action at all. A normal drive here would have me in the PWR range just to get to the top at 35mph.

 

to post #60: if this were the case, they would design it to use the engine to charge the battery and drive ev all the time. oh wait, that's how the volt works after it runs out of wall charge, and it gets terrible mileage.

 

That's my argument and seems to be the current thinking with the Prius except we constantly charge and discharge. I'm rarely using the ICE to charge. I'm passively braking and coasting using kinetic energy to charge my potential energy. Instead of constant P&G, which just momentarily cranks the ICE then shuts everything off, over and over again, never utilizing the battery, I'm using the stored energy. If I did the P&G all the time, I might as well not even have a battery to begin with.

 

your case maybe different because of the mountainous terrain.

 

Thank you. I'm just saying what I'm doing seems to work and maybe there isn't a one size fits all approach.

 

Yeah, your terrain allows you to follow the intent behind P&G if not exactly the letter.

Think of the intent as ICE operating at best efficiency, or off completely.
I drive this way in hilly terrain too: ICE up the hill, EV mode down. It is equivalent to P(ulse) up the hill, and G(lide) down.

And by the way, EV mode (the EV light is lit) does not require that power be used; only that the ICE not spin.

 

The ICE still spins, it just expends no gas.

 

Only if a speed threshold is exceeded. This is why we say 'glide' and not 'coast.' In my Prius Vagon, if the 'EV' light is on the car is gliding.

 

Yes. I did know that above 41mph (?) the ICE spins but uses no fuel. When coming back down from above the midpoint line, I completely let off the accelerator and depress it again and the EV indicator usually comes back on. I'm also finding I'm more comfortable driving in normal mode than ECO and still get about the same mpg's. I know it's psychological but the car doesn't seem as squishy to me. More responsive.

 

The threshold speed for no ICE spin in the G3 Prius series depends whether you reach it from a higher or lower speed. Assuming the battery SOC is in its happy area,

From above glide starts at about 43 mph, and from below 45-46 mph. I've always guessed that the differences are due to hysteresis, but that mostly reflects my not really understanding what hysteresis *is*