Do Hybrids Really Make Sense?

[niky]

I'm pretty sure sometime before those twelve years are up, oil prices will swing back up past $80 a barrel. Perhaps even by next year. At that point, you could probably lop off a year or two... or three... from the calculations.

But still... it makes more financial sense to downsize than to keep going for a big car with a hybrid motor. Which, I think, is reflected in the way hybrid sales are starting to lag in growth compared to regular car sales.

Then again, that could simply be the fickle buyers talking. Look at how they're running back to trucks now that gas is cheap again.

The EV market is still growing, but it will eventually find market saturation once the niche is filled. I doubt it will end up anywhere beyond 1% of the total market, however. Things will depend on what the next administration and other government do with those EV incentives in the years to come.

[Xist]

How would a hybrid be optimized for highway, would that impair its city driving, and how true is it that when a traction battery pack dies, it is usually just one cell, which can be replaced for a fraction of the price of a new pack, although with proportional results?

[redpoint5]

Originally Posted by niky

But still... it makes more financial sense to downsize than to keep going for a big car with a hybrid motor. Which, I think, is reflected in the way hybrid sales are starting to lag in growth compared to regular car sales...

The EV market is still growing, but it will eventually find market saturation once the niche is filled. I doubt it will end up anywhere beyond 1% of the total market, however.

I see hybrids as an intermediate technology. It's certainly not ideal because having 2 power trains in a single vehicle is crazy.

EV sales will go way beyond 1% at some point. Basically every family that has 2 or more vehicles is a good candidate for purchasing at least 1 EV.

Originally Posted by Xist

How would a hybrid be optimized for highway, would that impair its city driving, and how true is it that when a traction battery pack dies, it is usually just one cell, which can be replaced for a fraction of the price of a new pack, although with proportional results?

I think the Prius is optimized for highway travel. I get over 50 mpg at 70 mph, and the engine load is at 83%. That said, the same thing should be possible with a regular car with a CVT.

As far as reviving a failing battery pack, I think that very rarely the pack can be restored to good health with a single cell or group. Usually when a cell dies, the others are not too far behind. While you might be able to get things working again by replacing the weak cells, my guess is that further replacement would be necessary in the near future.

[oldtamiyaphile]

Originally Posted by redpoint5

I just ran the numbers on a new base model Ford Fusion vs the base model Ford Fusion hybrid and found the break even point is around 11 years of ownership at current fuel prices. I also ran the numbers on a base model Honda Accord w/CVT vs a base Honda Accord Hybrid and found the break even point is 12 years. This assumes 12,000 miles per year.

Are you using EPA numbers?

Since this is a hypermiler forum, I think that's a mistake. Most of us can beat the EPA by 30-50% with a regular petrol car, looking at the garage hybrids beat the EPA by 10-15%.

Just today I did my commute (15km of city driving, 20 sets of lights) at a recorded 5.7l/100km (41.3MPG), in my petrol van (roof racks, ladder on the roof, tow bar and full of tools). I followed this up with a 5.4 later in the day that's 80% over NEDC (9.7).

I'll compare to the 'big' Prius the V with an official 4.2 minus 15% for hypermiling that's 3.6 (65MPG).

Lets go with a peak fuel price from the last few years of $1.50/litre, and my 15,000km a year.

My van would cost $19,200 to fuel for 15 years
A Prius V would cost $12,200, so $7K saved over 15 years

How much does hybrid add to the cost of a vehicle? In the case of the Camry it's $5K over the equivalent petrol. If you're financing, that extra $5K becomes more than $7k, and if you're a cash buyer that $5 will become a lot more than $7k sitting in the bank. So even at 15 years, and assuming the hybrid battery lasts that long, it's still really hard to make the numbers work. That's before getting into the extra insurance of a more expensive car.

In short, hybrids make sense if you can only manage to match the EPA figures, and only long term. If you can get 50%+ over EPA out of your petrol manual it seems a hybrid is going to be a tough sell.

PS I tried to use your spreadsheet, but while I can view it online, I've been unable to download it. Looks good though

PPS I realise my comparison is a bit convoluted, the V is the closest hybrid I could get to my daily. It happens to cost double though

[RedDevil]

Looking at the garage the average hybrid beats the average gasoline car by a wide margin.
The hybrid in the middle of the hybrid list gets 51 mpg.
The car in the middle of the gasoline list gets only 32 mpg.
Only one hybrid in the entire list gets a lower mpg than that - a Toyota 4x4 Highlander...

Of course the average hybrid may have been designed more with economy in mind than the average gas car on the list.
Indeed the median over EPA % is just 4 for the hybrids and 15 for the gas cars.
Not that big a difference, but it is there.
That is only logical, as we are a hypermiling crowd, and hybrids do some of the hypermiling for us - giving us less remaining opportunities for improvement.
That difference is caused by hypermiling.

Yet in absolute terms the hybrids still beat the gas cars by more than 50%.
Makes sense?

[cowmeat]

Indeed the median over EPA % is just 4 for the hybrids and 15 for the gas cars.
Not that big a difference, but it is there.

Depends on the driver, lol!

[redpoint5]

Originally Posted by oldtamiyaphile

Are you using EPA numbers?

Since this is a hypermiler forum, I think that's a mistake. Most of us can beat the EPA by 30-50% with a regular petrol car, looking at the garage hybrids beat the EPA by 10-15%.

PS I tried to use your spreadsheet, but while I can view it online, I've been unable to download it. Looks good though

Very good points. I am using EPA numbers, but that is because the average driver outside of this forum only achieves EPA efficiency. It's not fair to compare a hypermiler that has made substantial aero improvements to their vehicle, with a typical hybrid owner.

Part of the disagreement in this discussion is that the question "do hybrids make sense" doesn't address the question of who does it make sense to. Does it make sense to a new car buyer? Does it make sense to a hypermiler? Does it make sense to someone whose commute is 98% steady freeway cruising? Does it make sense for someone that only wants 2 seats and no utility?

All I can do is reiterate the importance of choosing the proper tool for the job. A 2-seater doesn't work for my wife and I because we have friends and family. At least one of the cars must have a gasoline engine because we go on long distance road trips. The vehicle needs to have usable cargo capacity because of our outdoor activities, and I want something that is relatively comfortable to sleep in. Good fuel economy and low cost of ownership is also important to me. All of these factors pointed to the Prius. I bought my 2012 Prius plug-in with 32,000 miles for $13,400.

I would never say that Old Mech is wrong for choosing to drive his old Sentra. I have no argument that he should buy a hybrid instead. It sounds like the right vehicle to satisfy his needs. He probably sees the lack of Bluetooth connectivity as an advantage. That said, I could equally not say that hybrids are always unreasonable options. For some people, it makes sense as well as cents.

Thanks for giving the spreadsheet a whirl. I'll see if I can fix it so that others can download it. Feedback is much appreciated.

EDIT:
I tested the link to the cost of ownership spreadsheet, and you should see the following when you click it. There is a button to download the spreadsheet.

[oldtamiyaphile]

Originally Posted by redpoint5

Very good points. I am using EPA numbers, but that is because the average driver outside of this forum only achieves EPA efficiency. It's not fair to compare a hypermiler that has made substantial aero improvements to their vehicle, with a typical hybrid owner.

But with a typical manual petrol, the first 50% over EPA come without mods. I don't think your TSX is substantially aero modded, and my own Renault is aero de-modded with roof racks and a ladder, I've got an extra 200kg and still doing 40% over with the A/C on, while individual trips head into 80% over.

Take the weight and ladder off, switch off the A/C and I'd be looking at regular 100% over trips and with aero mods...

I don't think there'd be much left on the table with a hybrid.

[IamIan]

Just My 2 bits .. for the heck of it.

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Short Version:
Under any sufficiently varying load conditions a HEV system has a net energy efficiency (and performance) benefit compared to any ICE-Only option. But Energy Efficiency alone is not the only variable people use to choose. Use the right tool for the job.
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Stop hear / skip to next post .. unless you REALLY want the basic details of why that is the case.

Originally Posted by EVmetro

Apparently, the ICE is being used to charge the battery for the electric motor, but it is doing it at an an advantageous time. I don't know this for sure, but I do know that there is not enough regen energy available to supply enough energy to supplement the ICE enough to make up for what the ICE lacks in power.Using the ICE to supply energy for the electric motor does not make sense, but I am speculating that this is what is happening, and that it is happening at an advantageous time to minimize the penalty for doing it.

Let the cold emotionless math decide if it has enough or not .. or what makes sense or not .. For realistic expected conditions ... Than force yourself to accept that reality .. See Bellow.

Originally Posted by EVmetro

Is there anything unique to a hybrid other than the ability to harvest and redistribute wasted braking energy that can't be done on an ICE?

Yes... It improves the average operating efficiency of the ICE it's attached to .. under any sufficiently varying load conditions... but feel free to do your own math for other contexts and see where your own break even points are ... See Bellow.

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Initial Notes:
I am most familiar with my 2000 Honda Insight system .. so that is the one I used in the bellow.

The specific numbers (and break even points) spit out by the math will change (of course) if you change to other ICEs , other electronics, other conditions, etc... but the same science/engineering method can be applied to allow the cold emotionless math to spit out the answer (break even points, etc) for you for any known setup of ICE , HEV , conditions , etc.

The bellow 'summary' can easily be explored point by point in as much or as little additional depth as desired... but I figured it would be best to start with just the basic 'summary'.. Post is too long already as it is.

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Step #1 Define the variables.

#A> ICE-Only vs HEV system (access cost)

A common point raised is about the 'cost' (weight, efficiency , etc.) of adding a HEV system to a ICE-Only vehicle... so we will want to better 'quantify' that cost.

#B> Efficiency benefits HEV system vs ICE-Only System.

A common point raised is the efficiency benefits that HEV system gain that ICE-Only systems do not share ... so we will want to better 'quantify' that benefit.

#C> Efficiency / Performance ICE vs Electric Motor.

An ICE's operating efficiency and it's power out are far far more effected and varied over various RPMs/Loads than electric motors are... If you can have the ICE run 100% of the time only at it's peak efficiency point it's no contest the ICE-Only wins ... but , that isn't a realistic expectation of operating conditions ... sooo the only question becomes where is the break even point... We can use known operating (performance/efficiency) curves of the systems in order to better 'quantify' this variable.

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Step #2 Quantify Numbers

(1A)
The HEV system replaces the ICE-Only need for both Alternator and Starter .. sense it does both of those jobs as well... The weight of those from a ICE-Only get deducted from the HEV system weight in order to determine the net HEV system weight 'cost' for adding that HEV system.

Starter+Alternator = ~30 Lbs
HEV system that replaces those functions = OEM about ~120 Lbs

However it is possible (as shown) with KERS and other 'high end' components .. this weight (for same HEV performance) can be reduced to as little as ~30 Lbs.

OEM 120 - 30 = 90 Lbs HEV 'cost'
Minimum that Technologically would allow 30 - 30 = 0 Lbs ( HEV 'cost')

The weight effects the rolling resistance (no significant effect to Aerodynamic losses).

OEM 90 Lbs / ~1850 Lbs GVW = ~5% additional Weight
Minimum Technology would allow 0/1850 = 0% additional Weight

The rolling resistance Force increases linearly with increases in vehicle weight... F = Crr * N

The power (from Rolling Resistance) needed to move the vehicle increases linearly with weight ... P = F * V

Therefore the 0% to 5% additional weight will increase the rolling resistance by 0% to 5%.

The total vehicle needed power for any speed (flat) will be a combination of both Aero + Rolling resistances.

For the same OEM aerodynamics and tires .. the contribution ratio varies from over 90% Rolling under 13MPH ... to as little as 25% by 65 MPH... Which means the additional weight 'cost' is variable from as high as 5% to as low as 0% of the overall vehicle needed movement energy.

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(1B)
Regenerative braking is 100% gain for the HEV .. a ICE-Only vehicle will throw 100% of that energy away.

In heavy stop and go traffic this adds up quickly to large amount of energy.

In other types of driving it adds up slower ... I've read the 'average' US commute burns up ~6% of the fuel energy to braking alone .. Link.

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(1C)
See attached bellow efficiency curves for the ICE and IMA(Motor+Controller).

The combined IMA motor + Controller efficiency curve is over 90% or above for over about ~95% of the expected 'average' operating conditions.

I've tested the NiMH cells used ... in the window the BCM keeps them ... they are around ~90% cycle efficient ... that drops if the cells were taken into a wider SoC operating window ... but they aren't OEM.

So conservatively we know it will (in most cases) do better than 90% 90% 90% = ~73% Round Trip OEM cycle efficiency.

Again here .. there are Better motors , controllers, batteries available ... that could bring this up to ~90% Round Trip Cycle Efficiency... but that was not OEM.

This alone brings us to between 73% and 90% of that 6% 'average' wasted braking ... as much as 4.3% to 5.4% MPG gain ... just from braking ... for the 'average' US commuter.... which is already practically paid for the HEV system weight cost by itself .. and possibly already at a small 1-2% net gain for the 'average' US commuter... at higher (highway speeds) , the braking 'benefit' reduces .. but so does the MPG penalty from rolling resistance of the additional weight.

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Now looking at the ICE efficiency curve ... we see it varies from under 26% to as high as 38%.

Energy taken from the ICE at 38% going through the HEV system (73% to 90%) ... can be returned to the wheel at a net ICE to wheel of ~28% to 34% Fuel Efficiency ... Thus it is a net benefit to do so .. any time using the ICE-Only would have had a net operating efficiency bellow that net HEV round trip... The smaller 35% Lean Burn efficiency window can still net a HEV round trip from 25% to 31% ... which can still under some conditions be more efficient than forcing the ICE-Only system to run the ICE under it's worst efficiency conditions.

This is taken advantage of more so in the Prius than the Insight (but the principle still applies to HEVs in general).

- - - - -

Now looking at the difference in power curves.... see Attached

We see that the HEV system produces up to about ~50% of the total torque at low RPM ... without the HEV system the ICE-Only would either:

Take much much longer (under low ICE efficiency) to accelerate .. Which makes it less total net efficient.

Or ... as is the norm ... the ICE itself would get up-sized ... to a larger heavier ICE that still has 'enough' torque in the low RPM range... If you 'up-size' the ICE itself so that the ICE-Only can do all this low end torque itself ... the ICE growth weight penalty is larger than the HEV system weight penalty ... Compared to electric motors ... ICE's power to weight ratio's (at low RPM) SUCK horribly ... thus to double that ICE torque at low end ... it cost you far more ICE weight gain.

The other 'loss' from trying to upsize the ICE itself in a traditional ICE-Only system ... is that the much larger and much power powerful (at low RPM) ICE will now be even further away from it's higher operating efficiency range when not accelerating ... like on the highway cruising ans such ... which is a penalty to the ICE-Only ... the HEV style system tries to get a ICE sized small enough that it will operate dominantly in it's actual high efficiency range ... for the majority or the vehicle's "average" loads ... not sized for it's peak loads ... and let the HEV system take up the other 'short' periods when the vehicle needs additional torque/power.

[serialk11r]

Originally Posted by Hersbird

Some do it with the valve timing and some just can do it with the direct injection.

These motors I think always still have a throttle body but it's for startup and if something goes wrong with the system.

Diesels have been using direction injection without throttle for a long time with no fancy valve systems. It's their direction injection that made that possible

This is when quoting wikipedia is dangerous, and it helps to know how engines are actually designed and what regulations do what.

I'm not going to go into why a diesel doesn't need a throttle. Diesels are direct injection by definition and that has nothing to do with a throttle.

Ever wondered why diesel engines need NOx traps? Stratified injection would need an NOx trap as well because the cat would not be able to remove NOx with lean burn. No car in the USA has stratified direct injection, the only cars in this country that run throttleless are BMW N20, N52, N55, etc. engines, Nissan VQ37VHRs, and Fiats equipped with Multiair.