The problem with series hybrids

[dcb]

Flatlanders like me don't have a problem with the occasional hill, but have a problem with constant losses in the series transmission of power from engine to wheels. Can we not have a separate solution that is optimized to our locale? Or do we need to spend an extra $15k per vehicle and suffer series inefficiencies of the shlepping the extra baggage around in case a mountain suddenly appears?

If you do have hills, and find slowing down while climbing them to be so injurious as to merit such a complicated solution, then, well, I don't know what to say, except that it would be far more efficient to downshift back to bsfc on an extended climb than carry a bunch of extra and currently expensive stuff up the hill, and suffer transmission losses to boot.

[NeilBlanchard]

By adding a supercapacitor (that can charge/discharge at very high currents, and then can be used to either charge the battery at a feasible rate, or can be used to accelerate), and "learning" software controls, the percentage of electric regeneration can be increased quite a bit.

Dave, how would your ideal parallel hybrid be configured?

[bwilson4web]

This is a throughly enjoyable thread but I'd like to suggest:

• aging vehicle, individual repair costs decrease - what happens is the ones that fail from accidents get retired to a salvage yard and their remaining serviceable parts become the new source for transmissions, inverters, batteries, e.t.c. To claim "new car" repair costs 7-10 years later (aka., $8,000 for a battery) simply means the poster hasn't realized that individual repair costs go down over time. Heck, Orangeboy recently replaced a Prius transmission for a very low cost and there are a growing number of frugal, 3d party and do-it-yourself mechanics (aka., "Re-InVolt".)
• Toyota price reduction announced - "Toyota announced that pricing for first- and second-generation NiMH Prius hybrid vehicle (HV) replacement batteries have been reduced by more than 10 percent. The price of the 2000-2003 first-generation Prius battery has been reduced to $2,299, while the 2004-2008 second-generation Prius battery is reduced to $2,588. Prior to this most recent price reduction, both batteries were priced at $2985. " Sept. 2008.
• Partnership for Next Generation Vehicle included a hydraulic hybrid - before the program was killed for the hydrogen fool cells. There was a design for a pickup truck with hydraulic hybrid drive. Yet a decade later, they have yet to show up on the consumer market.
• Refuse pickup and postal vans - these are a natural home for hydraulic hybrids. I've long suspected the two-mode, Tahoes should have been hydraulic but we'll likely never know.

I try not to project performance numbers for technology I don't have 'in hand.' What I can do is offer some facts and data on our 1.5L NHW11 (2001-03) and 1.8L ZVW30 (2010) model Prius.

HILL CLIMB

Here are some benchmarks on an 8% grade hill near Huntsville Alabama. We are in the Tennessee River Valley and near the Piedmont Plateau:

Efficient Prius operation involves knowing optimum climb speed:

• 55 mph - the ICE is in a fairly efficient mode and this seems to correspond to hill climbing speeds of tractor trailer trucks. In short, I follow trucks up hills and match their speed (NEVER tailgating.)
• 65-70 mph - worst climbing speed in the 1.5L NHW11. The engine is running at peak power and has to enrich the mixture to cool the exhaust.
• +70 mph - the traction battery supplies the extra climb energy. The apparent fuel consumption goes down.
• 80 mph - our NHW11 finally depletes the traction battery just at the crest of the hill. Thereafter, an involuntary loss of velocity until flat land returns.

The 1.8L ZVW30 has significantly changed the hill climb profile:

The 1.8L engine incorporates a cooled exhaust recirculation system to reduce exhaust gas temperature. Also, the higher power output appeared to handle the hill climb energy. The only exception is use of a lower, 87 octane fuel appeared to put the car in traction battery drain mode above 80 mph.

There are aspects of the Prius transaxle that in one mode has elements of a series hybrid:

In normal mode, 1/3d of the power goes from MG1 and on to MG2. The MG1 counter torque is needed to allow 2/3ds of the power to flow through the planetary gear to the fixed, reduction gears. Using partial fractions, one can quickly calculate the Prius transaxle efficiency:

.33*(series_efficency) + .66*(mechanical_efficiency)

As for the Toyota patent issue, it has to do with using control computers to operate the transmission. The Toyota/Ford CVT system actually traces back to:

The classic electro-mechanical power split transmission developed by TRW and published in a 1971 SAE paper is the basis of today’s electric power split systems. G.H. Gelb, N. A. Richardson, T.C. Wang, B. Berman, “An Electromechanical Transmission for Hybrid Vehicle Powertrains,” SAE paper no. 710235, Jan. 1971 - "Comparative Assessment of Hybrid Vehicle Power Split Transmissions", Miller, John M., January 12, 2005

I am sympathetic that someone who doesn't have a Prius and believes they are competing with the Prius may not have current facts and data. Without 'skin in the game', it is easy to cite dated or in some cases, wrong claims. I'm just trying to bring current facts and data to the table. For example, traction battery replacement cost:


Other recommended sources:

• "Evaluaton of 2004 Toyota Prius Hybrid Electric Drive System" Stauton, R. H., Ayers, C.W., Marlino, L.D., Chiasson, J. N., Burress, T.A., ORNL/TM-2006/423, Dept. of Energy.
• "Development of New-Generation Hybrid System THS II - Drastic Improvement of Power Performance and Fuel Economy", Koichiro Muta, Makoto Yamazaki and Junji Tokieda, SAE 2004-01-0064.

I have more sources but these two are a good start.

Bob Wilson

[dcb]

probably one of the most discouraging things is the manufacturers won't release an EV without teaching it how to fart first.

[cfg83]

dcb -

Originally Posted by dcb

Flatlanders like me don't have a problem with the occasional hill, but have a problem with constant losses in the series transmission of power from engine to wheels. Can we not have a separate solution that is optimized to our locale? Or do we need to spend an extra $15k per vehicle and suffer series inefficiencies of the shlepping the extra baggage around in case a mountain suddenly appears?

If you do have hills, and find slowing down while climbing them to be so injurious as to merit such a complicated solution, then, well, I don't know what to say, except that it would be far more efficient to downshift back to bsfc on an extended climb than carry a bunch of extra and currently expensive stuff up the hill, and suffer transmission losses to boot.

This sounds like your are hinting at your separate "range extender" solution. If you were the hybrid king, how would you integrate/de-integrate a range extender? I don't think a hitch-on range extender would work from an automaker POV, but I can imagine an engine (and fuel tank?!?!?!) that could be "rolled into" a lowered trunk area via a detachable gurney. I think the average joe *might* accept a 30 minute installation/de-installation process, if his/her usage of said car allowed for maybe one install/de-install per week.

CarloSW2

[user removed]

Great inputs from everyone.

Going one a short vacation with my Parents (84 and 88) to Dover Delaware to play some slot machines. Not really my thing but the wife wants to go and yesterday was her birthday.

dcb, you could build some very small vehicles with my in wheel drive. You could also just use the front wheels for the power train.

You could also use a pressure washer engine and pump and make some very small lightweight vehicles with that as your power source.

I understand Bill that people who are not afraid of getting their hands dirty can keep them on the road cheap. I bought my 94 VX with 27,492 miles from a salvage yard in Ohio, in March 2008. Totalled and sitting inside an insurance training building for 13 years.

The odometer was at 52,400 yesterday, last tank was 55 MPG. so your point about skilled people finding inexpensive solutions is perfectly valid and I rebuilt 200 cars over my lifetime. That's a lot of recycled metal. When the local govt where my shop was located asked me how much we had recycled I told them 20 tons last year.

They didn't believe me.

I think you will see a lot more hh cars, especially in the X prize competition in the near future.

If you can build an inexpensive small lightweight hh that you can buy for prices that no Prius can touch as a new car, then the hybrid choice becomes much more mainstream.

After 60,000 hours of working on them, I know how complicated they have become. The design I propose takes that back to the simplicity of long ago. This will mean that in the future more people will take care of their own, and that makes transportation more affordable and reliable for everyone.

Be back Tuesday, good health to all.

regards
Mech

[user removed]

Originally Posted by cfg83

dcb -



This sounds like your are hinting at your separate "range extender" solution. If you were the hybrid king, how would you integrate/de-integrate a range extender? I don't think a hitch-on range extender would work from an automaker POV, but I can imagine an engine (and fuel tank?!?!?!) that could be "rolled into" a lowered trunk area via a detachable gurney. I think the average joe *might* accept a 30 minute installation/de-installation process, if his/her usage of said car allowed for maybe one install/de-install per week.

CarloSW2

Drive the electric version until you need to take a trip, then go to the range extender rental place and have them swapped in 5 minutes, pick up your battery pack when you return and they get their range extender back.

Rent the pack not the car. Much cheaper.

regards
Mech

[dcb]

not what I was thinking, as that would be a series setup with no storage, which is the worst of all.

I'll draw a picture.

[dcb]

so lets say you need an efficient continuous 15 hp 5 days out of the year with your EV?

This is how I would approach it from an efficiency/cost/low timeframe standpoint. Make a bolt on range extender (this is actually a "glorified" version of the motorcycle EV pusher) that runs at bsfc at 55mph for the average cruising load, and use the EV to get up to that speed (and to help on hills). It bolts to the BACK of the EV when needed and sits in a corner of the garage the other 360 days of the year.

Note: assume the EV can freewheel, and that you can also tilt up the range extender. Just lower it to "bump start" it when necessary, tilt it up for tight maneuvers. External fuel tank might be of concern to some, but putting it in the trunk could be worse, lets just say it uses biodiesel so it is less likely to explode

I needed an excuse to play w/sketchup anyway

[RobertSmalls]

Yep, that's one way to make a parallel hybrid. Here's an EV with a tow-behind diesel engine mated to a three-speed automatic transmission:

http://www.mrsharkey.com/pusher.htm