View Full Version : REEV concerns
James
01-13-2009, 10:32 PM
@james - of course GM will deliver the Volt! They are way too far down this path to not deliver it. The only real question is whether they hit their timeline and how many they ultimately produce or sell.
I have my doubts on that type of series hybrid ever being successful. I saw a presentation that walked through the energy flow of that system. The gas engine is only being used to recharge the batteries, not drive the wheels. So after the 40 miles of driving from the fully charged battery, that gas engine needs to generate a lot of electricity to maintain a normal speed vehicle. Many have speculated that the gas engine that GM is using cannot manage a normal driving speed after 40 miles. It would likely be in "limp" mode because that size gas engine cannot generate enough electricity to propel the weight of the Volt.
When the GM Volt is actually in the hands of independent reviews and car magazines, the weakness of the design will become obvious.
Toyota is going the right way with their plug-in design.
Just my opinion.
@james the issue in a series hybrid system isn't so much maintaining a speed, which requires relatively little power, but rather acceleration after the battery is "depleted". A Volt genset, if it had to handle the task alone, would have a very hard time passing someone on the highway. This is why they only have 8kWh usable but the overall pack is 16kWh. It gives them a lot of cushion to allow for the battery to add energy for acceleration even after the 8kWh is done.
There could be cicumstances where someone is doing a lot of hard accelerations and passing or maintaining high speeds for long distances where the pack will truly be depleted and the car's performance is significantly reduced.
I consider this a point of advantage for EV over series hybrid, but GM has designed around it so it isn't going to be a common problem. I don't know if fisker is doing something similar. They have spec'd 50 miles range with 20kWh which seems to assume the same Wh/Mile if they are also only using 10kWh as the usable range. Since Wh/Mile is likely to be higher than the volt, they will likely need to use more of the battery to achieve 50 mile range.
But the again they spec'd a very powerful ICE for the Genset so I imagine they can do more under genset power. Downside is poor efficiency.
James
01-14-2009, 07:26 AM
Siry, that is a good point. I had not considered that they might invade their reserve to maintain normal acceleration.
Regardless, I am sticking with Toyota (PHEV) and Tesla (EV) having better designs.
the issue in a series hybrid system isn't so much maintaining a speed, which requires relatively little power, but rather acceleration after the battery is "depleted".
Not only acceleration on the flats, but also maintaining speed on steep inclines, or into a strong headwind.
(Better not get stuck trying to accelerate uphill into a headwind... it does happen sometimes).
donauker
01-14-2009, 09:03 AM
I think this ongoing concern of the Volt not having adequate performance in some hypothetical worst case situation is way overblown. The power output of the ICE in a Prius is about the same as the generator output of the VOLT. The capacity remaining in the battery of Volt at the time it is considered depleted and the generator begins providing power is much greater then the full capacity of the battery in the Prius.
For the Volt to not have acceptable performance you will have to find a stretch of road where you would be able to keep the accelerator of a Prius to the floor for probably considerably more than 15 minutes and it would be under the speed limit for the entire time.
@donauker not a problem for a car like the volt but it was one of my major concerns when we considered REEV for WhiteStar since it was a sports sedan meant to be driven aggressively. Also - the "cost" of not worrying about this issue is a 50% usable range in the battery - that's expensive!
James
01-14-2009, 01:18 PM
Also - the "cost" of not worrying about this issue is a 50% usable range in the battery - that's expensive!
Siry, as I understand it, all of those mini-cycles are really hard on the battery. If I recall (I think I read this comment from you in an article) doing the Tesla battery system as a pure EV is far more simple and reliable for a long term life expectancy of 100,000 miles. Is that accurate?
I think the logic is based on this set of circumstances comparing an EV to a PHEV.
With a Tesla Roadster having a 244 mile range, most people will use around 10% to 40% of the battery pack each given day that the car is driven. So the battery will spend most of it's life between 50% to 90% charged up. This is actually a very good usage profile to maintain the long term quality of the battery pack.
With a GM Volt having a 40 mile range, most people will be using the full approved range of the battery each day. So that battery pack will be taken down to 30% charge on a regular everyday basis. I am assuming that the max charge is 80% and minimum reserve is 30%. So that 8 kwh of the 16 kwh is used. This type of regular deep cycling is fairly hard on the batteries over time.
Is that an accurate description of the situation?
@james - there is a key difference in cell chemistry. because of the cycle life issue you are describing, you have to use iron phospate (like A123) or manganese (like LG Chem) or other less common types in PHEV applications. These types of cells have lower energy density by a factor of about 2.
If you used cobalt oxide cells for a PHEV like the volt, they would not last 2 years (depends on a lot of things, but you get the gist). But in a pure EV like tesla, the pack is so big and contains so much energy that the lower number of cycles covers an awful lot of miles, so you see a longer life like you mention (along with all the temperature and charge balancing and other magic that treats the batteries nicely)
If you used these types of chemistries in an EV you would have a much shorter range (lets say 100-120 miles for the same weight). But a nice benefit would be you would have much better cycle life properties over time.
there is a key difference in cell chemistry. because of the cycle life issue you are describing, you have to use iron phospate (like A123)...
If you used these types of chemistries in an EV you would have a much shorter range (lets say 100-120 miles for the same weight). But a nice benefit would be you would have much better cycle life properties over time.
Yes, and some other wannabe EV makers are also trying to use LiPo because they don't have the capability to create a safety mechanism to keep the cobalt cells happy like Tesla did. (Or even if they did, Tesla's patents could get in their way).
SByer
01-14-2009, 08:25 PM
And again, I think we have to consider the PI Prius a whiff because it's got 0 EV-only miles. We can dis GM for it's bad labor deals and parts-bin engineering, but with the Volt, they're really trying. Toyota gets credit for first attempting the complex through-the-drivetrain hybrid they did (I'm looking at you Honda, and that super-cheesy through the road junk you tried). But that was years ago, and now they're just looking like all they want to do is greenwash.
It's 2009. If you can't do at least 20 highway miles EV-only, you're not at the leading edge.
Bloomberg.com: Japan (http://www.bloomberg.com/apps/news?pid=20601101&sid=ad4Cv1yuB.Gk)
The new Prius adds software to recommend to drivers more fuel-efficient habits. The 2010 model also offers three different drive settings including “EV” mode that lets the car go as far as 1 mile (1.6 kilometers) using only electricity from its nickel-metal hydride battery packs.
But the Volt still isn't on the road, and there are over a million Prius so far.
Also the Prius is supposed to be the most aerodynamic car available.
For an around town, urban vehicle, the Volt will probably be more efficient due to PHEV, but if you needed to drive a family of four long distances, the Prius may still be a better way to go.
James
03-06-2009, 10:34 AM
It seems that the GM Volt design will have a key weakness during certain scenarios.
Since the ICE is only recharging the battery, and it does not recharge fast enough to maintain high acceleration/fast driving, this creates the potential for really horrible performance.
If you have been driving 40+ miles already and your VOLT battery is drained of your electric grid charge, then it is likely has a state of charge around 30% to 40% when the ICE kicks on to recharge.
So now you have to do a hard acceleration to deal with a hill or some other high energy consumption driving scenario. Supposedly the GM Volt will allow you to invade the battery reserve for a while. But what if you do this to the point where the state of charge gets really low.
Then you are in a serious limp mode where you really only have the energy available based on the ICE recharge rate.
How many watts is the on board ICE recharging at?1,500 watts? 2,000 watts? That is enough to allow about 5 to 8 miles of range per hour.
This is just speculation. But I imagine that the battery could get into a charge level where the performance is just pathetic.
James, I have been saying the same thing for a long time.
Some had even claimed you could get by with only a 20hp ICE generator in a "REEV/eREV", but only providing steady state flat highway cruising HP doesn't seem nearly enough to me.
Getting from Here to There « Tesla Founders Blog (http://teslafounders.wordpress.com/2008/01/14/getting-from-here-to-there/)
The Volt will only charge to 80% and will run only on battery power to 30%. Once at 30%, the generator will kick for “charge sustaining mode”…I’m hoping there is a good engineering reason behind this, but it seems odd to make this decision before deciding on the ICE technology.
Jan 17, 2008: I made some comments about this design on the Tesla blog a while back. I think the reason is because they want to market the REEVs as a 40+ mile range BEV, and the ICE is supposedly only for “emergency range extension”. If people only ever use the vehicle for a <40 mile commute with a full recharge cycle at the end, then fine. But my concern is what happens when you run the pack down then need sustained power beyond what the ICE generator will provide. My example was a drive from San Jose to Lake Tahoe. You use up your BEV capacity just as you get to the base of the mountains. Now you want to make the run up the hill on fast moving highway 80 and you have a full load of people, gear, and a ski rack on the roof. The wimpy little ICE is going to be hard pressed just to keep you going at full speed and really have little left to recharge the pack then.
I really think this design will only work out if you have a way to force the ICE on early because you know you are going on a longer than usual drive. Fisker seems to offer this with their stealth vs performance paddles. I hope Volt and other REEVs offer a way to override the “default” ICE avoidance behavior.
...the SF bay area to Tahoe example is tough because many people do that drive in one sitting and the big climb is at the end. It is 87 miles from SF to Sacramento so you almost certainly have drained your batteries by then. Then the climb from Sacramento (at sea level) has to climb to 7000feet to get over Donner Pass (http://en.wikipedia.org/wiki/Donner_Pass) I still think a 70hp ICE running a generator through to an eMotor is going to make that hill climb problematic when other cars are holding on to 65-70MPH the whole way.
I wouldn’t put a lot of stock in public comments about the control algorithms of these various REEVs. They are written by marketing people who massively over-simplify what the engineers are doing. My bet is that none of the REEV players - not GM, not Tesla, not Fisker - are anywhere near done designing and tuning the control algorithms for engine and battery behavior. I also bet that when they are all done, every control algorithms will be so complex that a simple statement like “the engine starts when the state of charge reaches X” will be a meaningless simplification
Reading through comments about charging spots, something occurred to me. What about when someone brings in a REEV that has run down both the tank and the batteries. Now we have a use for “dual refueling”. They could charge your batteries while they fill your tank. That way you get more EV miles rather than expecting to use some of the fuel to recharge the batteries. Mixing high voltage with gasoline pumps at the same station sounds like a controversial/risky undertaking, but it would make some sense to those who want to “maximize all electric miles” of REEVs.
REEV Concerns:
...maintaining speed on steep inclines, or into a strong headwind.
(Better not get stuck trying to accelerate uphill into a headwind... it does happen sometimes).Martin on Tesla blogs (http://www.teslamotors.com/blog2/?p=27):
Several of you have suggested installing a gasoline (or other fuel) generator in the trunk of a Tesla car as a range extender. Such a feature would convert the Tesla car into a form of plug-in hybrid. ... Note that the gasoline engine for such a hybrid car has to be pretty much as big as a car engine, since it ultimately must power the car by itself when the batteries are exhausted. Don’t think about that 1-cylinder, 1-kW Honda generator you can buy at Home Depot; think Prius engine, at least.
Teslamotors blogs (http://www.teslamotors.com/blog3/?p=70):
# Jason M. Hendler wrote on December 13th, 2007 at 3:31 pm
## I think your estimate of 50 HP to maintain highway speeds is an order of magnitude too high.
TEG2 wrote on December 13th, 2007 at 4:49 pm
You really think you could have a 5HP generator in a large, heavy family sedan and make it maintain good highway speed as long as the fuel lasted?
I mentioned 50HP because I was considering cases where you are driving uphill at 75MPH into a headwind with a full load of luggage strapped to the roof, and maybe even pulling a trailer. If someone wants to take a ski trip from San Jose to lake Tahoe and never have the vehicle restrict your speed potential I think you would need a lot more than 5HP to ensure that they batteries don’t run out of charge and spoil your driving experience. San Jose is to Lake Tahoe is a trip many from Tesla could contemplate. It was in fact one of the “demo” drives that was done to show off the Roadster. In the case of a series hybrid, I would envision that trip would go something like this… Customer drives from San Jose all the way to Sacramento just on battery power (because the system is optimized to try to avoid use of the ICE as long as the batteries have charge). Just as you start to head up highway 80 the computer realizes that the batteries are almost drained and fires up the ICE. Now you are headed up a steep incline with 70MPH+ traffic and you want to get to your cabin before dark (or before the lifts open if you left early in the morning). You better have enough ICE HP to maintain that speed uphill and hopefully even start charging the batteries at the same time because you may need some extra battery power for passing opportunities. Also if the ICE won’t run itself when you park you don’t want to end up in Lake Tahoe with a completely drained set of batteries. I would be concerned about trips like this if it had a whole lot less than 50HP of ICE power available.
donauker
03-06-2009, 12:03 PM
Then you are in a serious limp mode where you really only have the energy available based on the ICE recharge rate.
How many watts is the on board ICE recharging at?1,500 watts? 2,000 watts? That is enough to allow about 5 to 8 miles of range per hour.
This is just speculation. But I imagine that the battery could get into a charge level where the performance is just pathetic.
It has been stated that when the Volt reaches the end of its all electric range it will go into "charge sustaining mode" this basically means that the ICE/generator will begin providing the power for the electric drive motor. If more power is temporarily needed by the drive motor than can be provided by the generator it will be drawn from the remaining 30% charge level in the battery and when less is needed the excess will be used to restore the charge level to 30%.
The reason for doing this is that the electricity produced by the ICE is several times as expensive as the electricity available from the receptacle in your garage and it would be a shame to finish charging the battery just as you arrived at your next plug in spot.
There sure does seem to be a lot of misperceptions about the power available from the ICE/generator used in the Volt. We are told here (http://en.wikipedia.org/wiki/Chevrolet_Volt) that it is a 53 kW generator. And based on Tesla information here (http://www.teslamotors.com/blog4/) (shown below) that is sufficient power to keep the roadster going at a sustained 103 mph. That is certainly enough to keep the Volt moving along at much greater than safe speed since as you can see below only half that power will keep the roadster moving at over 75 mph.
https://www.teslamotors.com/display_data.php?data_name=range_blog3
It takes a lot more power to go up a steep hill than it does to maintain speed on the flats. Those charts don't tell the story of how well it will do loaded up with cargo trying to climb a mountain pass.
Yes, for most driving situations it should be plenty fine, but I still think there will be occasional situations where you find it lacking.
Related reading:
More on How Much Power You Really Need | AutoSpeed Blog (http://blog.autospeed.com/2009/01/29/more-on-how-much-power-you-really-need/)
donauker
03-06-2009, 12:42 PM
It takes a lot more power to go up a steep hill than it does to maintain speed on the flats. Those charts don't tell the story of how well it will do loaded up with cargo trying to climb a mountain pass.
Yes, for most driving situations it should be plenty fine, but I still think there will be occasional situations where you find it lacking.
There may well be a place or two in the country where you could find a situation that would be a problem but it would also be a problem to a lot of other vehicles. It would be easy to test it with a loaded Prius. Take the Prius there and push the accelerator to the floor for 20 minutes. If you never reach a speed where you need to lift your foot, the Volt may also slow to the speed of the Prius at that point.
...the Volt may also slow to the speed of the Prius at that point.
I bet the inverter and eMotor efficiency loses in the Volt will be more than the CVT losses in the Prius' more direct coupling to the drive wheels.
Driving in the mountains - Any problems - PriusChat Forums (http://priuschat.com/forums/prius-main-forum/35193-driving-in-mountains-any-problems.html)
I had an driving experience last week with mountain driving. I had four adults in car at ~8000 ft. climbing a steep grade, down to one purple bar (or less) with A/C on, with temperature in 80's. Needless to say, the car didn't have a lot of power... I wouldn't like to drive under these conditions for long periods of time, fortunately it was an unusual situation.
We returned from a 7,500 mile trip a week ago today. It included crossing the continental divide a few times as well as other mountain climbing. We chose not to just let the engine roar, so we got down to 35 mph at times. However we were fully loaded-- two adults, two teens, two tents, all camping gear, roof rack, etc.... Not maintaining maximum speed on the steeper mountains was fine with us. Be patient and enjoy the beautiful scenery!
donauker
03-06-2009, 02:17 PM
I bet the inverter and eMotor efficiency loses in the Volt will be more than the CVT losses in the Prius' more direct coupling to the drive wheels.
I assume you are aware that the "CVT" in the Prius is not actually a CVT. At the heart of the Prius "CVT" is a planetary gear set which works as a power split device. The net result is that 72% of the engine torque is directed through reduction gears to the front wheels. The remaining 28% is directed to a motor/generator working as a generator producing electric which is used to either charge the battery or is inverted and used to drive a second M/G which is also connected to the front wheel final drive.
This design is amazing in the way it works but it also means that at least 28% of the power produced by the ICE is subject to double conversion loses.
The point I have tried to make centers on the difference between peak power need and long term continuous needs. That is why I challenge anyone to find a place in the US where you can keep the Prius floored for 20 minutes none stop. It is only after that duration that the Volt may become comparable in performance. Given the number of Priuses on the road I think we can live with comparable in this yet to be found location.
OK, Don... My main beef was with those who initially claimed that ~25hp would be enough ICE power when they saw charts that said that is all that is needed to maintain highway speeds.
GM ended up using a more Prius sized ICE, and 53kWh is probably enough nearly all of the time with that healthy battery assist for occasional passing requirements. I am content to wait and see if any Volt owners complain about long hill climbs or not. It might be acceptable, but time will tell.
I assume you are aware that the "CVT" in the Prius is not actually a CVT.
Yes, I have a Synergy drive vehicle myself.
Toyota does call it a CVT.
Prius Glossary (http://www.toyota.com/disclaimers/ecvt.html)
CVT is a type of transmission with an infinite number of gear ratios that are always changing depending upon the relative speed of the vehicle and the engine rpm. There are several types of CVTs. Hybrid Synergy Drive® uses an electronically controlled CVT (ECVT) which integrates a planetary gear set into the drivetrain.
By the way, for whatever reason, Toyota has decided to increase ICE size for the 2010 model:
Toyota's 2010 Prius breaks cover (http://www.gizmag.com/toyotas-2010-prius-breaks-cover/10756/)
...The move from 1.5 liter to a larger and more powerful 1.8 liter Atkinson-cycle, four-cylinder engine should significantly improve the power to weight ratio and the performance of the Prius. The current 1.5l Prius has always scored well in city driving due to its regenerative braking but it has been noticeably lacking in highway performance due to its small engine capacity and the additional weight of a battery pack compared to vehicles with similar engine capacity. Contrary to conventional wisdom, the larger engine actually helps improve highway mileage. By making more torque, the new engine can run at lower average rpm on the highway. When operating at lower rpm, the new engine uses less fuel.
The 4 cyl VVT-I puts out 98 hp (72 Kw) @ 5,200 rpm with 105 lb/ft (142 Nm) @ 4,000 rpm compared to 76hp (57 Kw) and 82 ft/lb (111 Nm) in the current model.
Slightly related discussion:
High revs uphill - GreenHybrid - Hybrid Cars (http://www.greenhybrid.com/discuss/f26/high-revs-uphill-2839/)
Prius and steep inclines - PriusChat Forums (http://priuschat.com/forums/prius-technical-discussion/55180-prius-steep-inclines.html)
I must say, my experience on the grapevine was slightly different. It was one of the only two times that I felt my car wasn't quite powerful enough. Don't get me wrong, the Prius is a great car and handles everything nicely. It's just occasionally you might wish it had a little more oomph.
Anyway, onto the story.
I was headed southbound and all was fine. There was enough power, I had enough to noticeably accelerate with, too. That is, until the the last couple miles or so on the final uphill stretch. I was slowly falling behind traffic (which was cruising around 72 mph...but increasing!) and I found myself pressing the accelerator lower and lower. Finally, with the pedal floored I was going 76 mph with cars continuing to pass me. Even highway patrol decided to go around me. Needless to say, I was a little disappointed -- for the first time -- not because I couldn't keep up (I could, just barely) but rather I had no margin for safety. I was literally maxed out.
If you're wondering when the only other time was, it was southbound on highway 5 (ironic that it's the same freeway) somewhere near the Oregon-California border. Although this time the car was loaded with people and luggage. Again, it wasn't that I couldn't keep up, it was just the fact that I didn't have anymore room for a "just-in-case boost."...
...I'm beginning to think that some running algorithms were changed
around '06 to manage the pack charge a little differently when
moderate to heavy power is asked of the engine and a larger
throttle opening is necessary at higher altitudes. My '04 took the
SOC down to one pink bar [from only 3 or 4 blue!] on the way over
Vail and Loveland in CO this summer [11000 feet or so] and with
nothing left in the battery, I was on the engine alone and having
to push it right up to 4000 or 5000 RPM to match "normal" traffic.
At 78 HP or less that is a bit anemic for the weight of the car, but
I was perfectly fine with climbing more slowly and waiting it out
like any loaded semi would.
Avoid (http://prius.ecrostech.com/original/Choosing/Avoid.htm)
Do You Regularly Drive in Mountains?
The Prius will not climb very steep hills indefinitely. One aspect of the vehicle's design that drastically improves economy and reduces emissions is that the engine is not sized for the peak power demand. When heavy acceleration or steep hill climbs are called for, MG2 (http://prius.ecrostech.com/original/Glossary.htm#MG2) provides a boost to meet the performance needs using power from the battery. Although heavy acceleration can't go on for very long and the battery gets a chance to recharge, in some parts of the world you can find steep hills long enough to drain the battery to its lower limit. At this time, you have only the ICE power to run with and you'll be forced to slow down. You'll still make it to the top. People have driven to the top of Mount Washington, which averages a 12% grade for more than seven miles. But, after the battery power is gone, the maximum speed (according to my calculations) will be about 40 m.p.h. Not being able to climb Mount Washington at 60 m.p.h. is, of course, no reason not to choose a Prius. But, if your daily commute happens to be over the California coastal range or some other long steep hill, joining the trucks in the extra slow lane might wear a bit thin after a while.
Nice explanation of Toyota's Synergy Drive "power split" device (http://prius.ecrostech.com/original/Understanding/WhatsGoingOnAsIDrive.htm).
(yes, eCVT is a bit of a misnomer, but Toyota does use it too).
How much power to maintain speed? (http://www.insightcentral.net/forums/modifications-technical-issues/13275-how-much-power-maintain-speed.html)
...
22 HP to maintain 55 MPH
...
50 HP will maintain 55 MPH up a 6-7% grade.
...
...Also going up even a 1% incline will change the results as well...
rolling resistance will be reduced by 1% as the normal force against the road is no longer the whole weight...
so ~6.57 Watts less rolling resistance... but you traded it for gravitational force acting against you... which means ~1% of the gravitation force of the car becomes a counter force... or about 834*9.8*0.01= ~81.732 N * 13.411 = ~1,096 Watts = ~1.1kW of gravitational resistance to even a 1% incline...
...Gravity:
as you go up an incline your normal force for the rolling resistance will be decreased.
So a 1% incline will reduce your rolling resistance to 99% of the 0% incline rolling resistance.
while at the same time adding 1% of the vehicle weight as a pull against you... 834 * 9.8 = 8,173.2 * 0.01 = 81.732 N
...
donauker
03-09-2009, 12:11 PM
Nice explanation of Toyota's Synergy Drive "power split" device (http://prius.ecrostech.com/original/Understanding/WhatsGoingOnAsIDrive.htm).
(yes, eCVT is a bit of a misnomer, but Toyota does use it too).
Yes, this is the single best source of information on the Synergy Drive I have ever seen. Oddly enough it was this site that several years back started me down the road to electric.
Being a techno geek all of my life and a computer programmer most of it, I was intrigued by the complexity/simplicity of the Synergy Drive. After studying all of Graham's writing's in depth I just had to have it and purchased my Lexus 400h. The brief periods of electric only drive lead me to trying to maximize electric mode which of course became frustrating in how limited it was. After a few months with the Lexus I decided any new personal vehicles I would purchase would need to have a plug and a substantial electric only range.
Same story for me basically.
My wife's Highlander Hybrid (same drivetrain as the 400h) sits in the driveway next to my RangerEV, which was the most I could afford to get myself a plug in vehicle with decent range, and batteries that will last more than a few years.
The Highlander will be our long trip car, and hopefully the RangerEV gets replaced by a "BlueStar", SmartEV, MiEV, or some such affordable EV once the Ranger eventually wears out. Perhaps "Model S" if something miraculous happens, but I am not holding my breath on that right now.
graham
03-09-2009, 03:31 PM
After studying all of Graham's writing's in depth I just had to have it and purchased my Lexus 400h.
He is a different and much more knowledgeable Graham, just in case there was any confusion! :smile:
Just a quick (probably uninformed) question .... but it seems like the issue with the Prius on hills/mountains is primarily due to the relatively small battery that drains too quickly to provide any useful impulse on a hill. With the Volt, the battery is substantially longer and should be able to provide full power on a hill ... provided that the hill is not too long (many miles of mountain/hill driving) or the battery is not too fully depleted when starting.
Question: Couldn't the problem be substantially addressed by a toggle switch for the driver to let the car know to keep the battery nearly fully charged. i.e. if you know you are driving up to Mammoth Mtn, then tell the car, and it will maintain the battery at full charge state. A fully charged battery plus the engine should be able to last quite a while -- 40 miles of mountain, minimum, by definition.
Similarly for a range-extender on the Tesla: if you turn on the range extender when you start driving, then even a small range extender should be able to get you quite a distance. i.e. 250 miles nominal electric mode + (3 charging hours while you're depleting your electric range * 25HP) + (whatever time that buys you * 25HP). I expect the result would extend the range out to ~500 miles...
Dan.
...Couldn't the problem be substantially addressed by a toggle switch for the driver to let the car know to keep the battery nearly fully charged.
Or include an inclinometer in the car and in a setup menu tell it what angle you want to kick in the ICE,
Couldn't the problem be substantially addressed by a toggle switch for the driver to let the car know to keep the battery nearly fully chargeYes! I had been saying that before. If you started on a drive from SF to Tahoe and flipped the "try to keep my battery at least 80% full" switch as you left, then the ICE would come on sooner, and you would start uphill past Sacramento with plenty of charge to 'make the grade' uphill without problem. The possible problem (as I see it) is the weak ICE coupled to a strategy of "drain the pack first" with no option to override.
Another option would be to have it GPS/Nav coupled and it calculates what you need based on the destination you programmed in at the start of your trip.
Couldn't the problem be substantially addressed by a toggle switch for the driver to let the car know to keep the battery nearly fully charged.
I would think just integrated with GPS, which should have elevation and road speed data. Similarly you want the battery near empty when you return home for full benefit.
Takumi
03-09-2009, 10:19 PM
This thread is very similar to using the Roadster as a grocery/long distance vehicle. It should be used just as GM is intending it for. The range extender used only when one miscalculates one's travel distance for the day.
REEV concerns should be about the product not meeting the manufacturers stated performance. What I've read here so far is like the analogy of buying treadmill and then hanging clothes on it instead of exercising on it.
Use the Volt as it is intended. Plug it in nightly and pay the premium for the peace of mind that you can forget every now and then yet not get stranded when you need it most.
What I got from this thread, so far, is that if you are in the city (travel 40 miles or less) and in the market for a hybrid, buy the Volt. If you don't want to plug in, buy the Prius.
BTW, how far off do you think GM will be with the Volt launch? Will it launch with more or less bugs than the Roadster?
stopcrazypp
03-09-2009, 11:33 PM
BTW, how far off do you think GM will be with the Volt launch? Will it launch with more or less bugs than the Roadster?
I think even with them rushing to get the car to market, it will have less bugs than the Roadster. After all, they are still a large automaker and they have fairly strict testing. I think they have already evaluated what potential bugs may pop up and have, for the most part, parts lined up and probably testing for at least the initial release.
The question is if the company survives long enough for the car to be released.
Don, something else I just noticed:
2010 Toyota Prius Sales Will Hit 100,000 in 2009, Toyota Says | Straightline Blog on Edmunds' Inside Line (http://blogs.edmunds.com/straightline/2009/03/2010-toyota-prius-sales-will-hit-100000-in-2009-toyota-says.html)
Other efficiency improvements this year include a smaller, lighter front transaxle that's gear-driven rather than chain-driven to reduce friction. A new planetary reduction gear allows the front-drive electric motor to run at higher rpm -- a 13,500-rpm max compared to a 6,400-rpm max previously. The inverter is also smaller and lighter, thanks to improved cooling.
Old vs New (2010) Prius transaxle:
http://blogs.edmunds.com/straightline/oldandnewtransaxles.jpg
Joseph
03-10-2009, 07:42 PM
The chain is gone!!! I always found it humorous that the Prius used a chain. (did the other toyota hybrids use a chain also?) I wonder why they got rid of it. To improve packaging? Efficiency?
On the whole "ev mountain climbing deal," none of matters. The EV market is tiny and production figures will be modest in the near future. Neither the market nor the problem is large enough to make mountain driving/speeding a limiting factor in the short-term success of EVs.
The chain is gone!!! I always found it humorous that the Prius used a chain. I wonder why they got rid of it. To improve packaging? Efficiency?
It was in the quote:
Other efficiency improvements this year include a smaller, lighter front transaxle that's gear-driven rather than chain-driven to reduce friction.
donauker
03-11-2009, 06:03 AM
TEG,
Thanks for that picture. The original design was amazing in its compactness and the new one is truly a work of art! Adding the gearing to MG2 thus allowing for a higher rpm / lower torque motor design saved a good bit of space.
dpeilow
04-06-2009, 08:06 AM
Elon takes a swipe at REEVs, Jalopnik takes a swipe at Elon: Jalopnik - Tesla's Elon Musk Continues War Of Aggression Against Volt, REVs - elon musk (http://jalopnik.com/5200209/teslas-elon-musk-continues-war-of-aggression-against-volt-revs)
I don't think there is much here that hasn't been said before, just gawker et al raking up old stuff.
Ya know, I read that this morning from GM-Volt.com. I preferred the version without all the editorializing.
Tesla CEO Critical of the Chevy Volt | GM-VOLT : Chevy Volt Electric Car Site (http://gm-volt.com/2009/04/06/tesla-ceo-critical-of-the-chevy-volt/)
Joseph
04-06-2009, 02:03 PM
Just compare the titles of the two articles.
Elon response summed up all the difficulties of REEVs well, sweet and simple.
Ya know, I read that this morning from GM-Volt.com. I preferred the version without all the editorializing.
Tesla CEO Critical of the Chevy Volt | GM-VOLT : Chevy Volt Electric Car Site (http://gm-volt.com/2009/04/06/tesla-ceo-critical-of-the-chevy-volt/)
But those commenters have a few things to say...
edit to add
Oh Looky at number 71... KB is alive and piling on Elon
kent beuchert Says:
April 6th, 2009 at 9:43 am
2011 Chevrolet Volt First Drive - Car News/Green Machines/Car Shopping/Hot Lists/Reviews/Car and Driver - Car And Driver (http://www.caranddriver.com/reviews/hot_lists/car_shopping/green_machines/2011_chevrolet_volt_first_drive_car_news)
via
What Will the Volt’s Generator Mode Feel Like? | GM-VOLT : Chevy Volt Electric Car Site (http://gm-volt.com/2009/05/04/what-will-the-volts-generator-mode-feel-like/)
What isn’t yet clear is how the Volt will behave when the battery is depleted and the gasoline engine kicks on to provide more juice. In this so-called range-extending mode, the electric motor will be limited to the power provided by the 1.4-liter four-cylinder engine under the hood. The gas engine is never used to charge the battery; the engine turns a generator that directly feeds power to the electric motor. If the engine is revving at 2000 rpm and making 25 hp, the electric motor will only be able to make 25 hp. If more power is needed, the gasoline engine could conceivably run at its power peak at a very high rpm. Taking the point further, if the gas engine is only rated for 100 hp (our estimate of its power output), the 149-hp electric motor will only be able to make 100 hp. The upshot: the Volt will be quicker running on battery power than it will be when the gas engine is providing the electricity.
Unable to try the gas-fired solution for ourselves, we asked Posawatz how the experience will change when the battery is discharged and the gas engine kicks on. “The work being done by the development guys as we speak is to create a gentle feathering of engine rpm,” he said. “So you don’t even notice that the engine kicks in. And to try to operate at the right points and to transition the rpm points depending on the load you’re getting—to behave like someone would want it to behave. You may get into a position under an extreme grade or hill climb, where the engine rpm will be pretty loud—running pretty hard. At a certain point in time that rpm will be relatively unpleasant. This is the challenge of different road loads: how can we keep the NVH reasonable for a customer?”
ChargeIt!
05-04-2009, 10:22 AM
I am (again) getting more disappointed:confused: in the Volt.
I had been under the impression until now that the gas engine charges the battery for use by the electric motor. Now this ! :rolleyes:
How complicated can you get ? (Leave it to GM to proving that ! :eek:)
efusco
05-04-2009, 10:30 AM
The gas engine is never used to charge the battery; the engine turns a generator that directly feeds power to the electric motor. If the engine is revving at 2000 rpm and making 25 hp, the electric motor will only be able to make 25 hp. If more power is needed, the gasoline engine could conceivably run at its power peak at a very high rpm. Taking the point further, if the gas engine is only rated for 100 hp (our estimate of its power output), the 149-hp electric motor will only be able to make 100 hp. The upshot: the Volt will be quicker running on battery power than it will be when the gas engine is providing the electricity.
That just doesn't sound believable. I have to assume they're mistaken. That certainly isn't the original concept released and just doesn't seem to make sense...why run the ICE like that where it's RPM bounces around depending upon load and thus rarely in it's most efficient range.
It makes so much more sense and is conceptually more logical to run it always in a very high efficiency rpm range to charge the battery...unless they're afraid it wouldn't be able to sustain the battery SOC at times and had to change the design concept. And if that's the case, they could be on their way to failure of this concept...IMO.
graham
05-04-2009, 10:40 AM
It sounds to me that one of their design considerations was trying to reduce the engine noise. So instead of running the engine full-tilt, they run it pretty slowly (quietly) unless the drain on the battery is so high that they have to run the engine at full tilt (along with its engine noise and gas usage). If they can reduce the engine to running only at bare minimum, they will have a quieter car and can claim higher gas milage over short trips.
It also sounds like (unfortunately) people don't like the ICE to have a mind of its' own. They want the ICE RPMs to correlate to pedal position to some degree. So if you aren't accelerating, people don't want the ICE to start revving too much. Again this works against the idea of only running the ICE at most efficient RPM, and the idea of having it come on to charge batteries then shut down again once it has enough charge. Basically people want what they are used to, and so it sounds like these series hybrids are being designed to act as an EV for a while, then act as if the ICE is connected to the wheels in some way even though it isn't.
Kevin Harney
05-04-2009, 12:14 PM
I never thought of that until you said it. But I can tell you I would be a little bit concerned if my car was always at a high speed idle even if my foot was off the gas. That would be disconcerting until you got used to it. No focus group would really have time to get used to it.
Not to mention how hard it's going to be to settle on an equitable number representing MPG (or GMP).
Kevin Harney
05-04-2009, 01:41 PM
It should be some form of energy storage like joules / mile or what ever is the best value other than joule. All energies should be converted at that rate. Amount of energy in a gallon or in a Kwh or in H2 or whatever.... center us on ENERGY used not anything else.
Exclusive: The Engineering Challenges of Volt Generator Mode | GM-VOLT : Chevy Volt Electric Car Site (http://gm-volt.com/2009/08/17/exclusive-the-engineering-challenges-of-generator-mode/)
Wow, Tough calls to make.
For some they will make some big mistakes in what decisions are ultimately made, just like Tesla.
For them it's even more dammed if you do, dammed if you don't.
Tdave
08-18-2009, 06:45 PM
They're putting way too much emphasis on "what the driver expects". This is a new paradigm. Time to reinvent what the driver expects. Just do what's best for efficiency and/or performance.
Will the Volt Have Power Limitations on the Highway? | GM-VOLT : Chevy Volt Electric Car Site (http://gm-volt.com/2009/08/21/will-the-volt-have-power-limitations-on-the-highway/)
Will the Volt Have Power Limitations on the Highway? | GM-VOLT : Chevy Volt Electric Car Site (http://gm-volt.com/2009/08/21/will-the-volt-have-power-limitations-on-the-highway/)
Finally they come clean. I mean it's fine that the car can't do everything. No car can. Sometimes these guys should just say what the design intent is and then target those buyers.
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Doug's at 3000 Posts!
If you started on a drive from SF to Tahoe and flipped the "try to keep my battery at least 80% full" switch as you left, then the ICE would come on sooner, and you would start uphill past Sacramento with plenty of charge to 'make the grade' uphill without problem. The possible problem (as I see it) is the weak ICE coupled to a strategy of "drain the pack first" with no option to override.
Another option would be to have it GPS/Nav coupled and it calculates what you need based on the destination you programmed in at the start of your trip.
Yep:
GM Volt will offer 'Mountain Mode' for hill climb charge preservation (http://www.allcarselectric.com/blog/1044806_2011-chevy-volt-to-offer-mountain-mode-for-hill-climbing)...
...under a "limited set of circumstances," on a handful of known grades in the country, vehicle (http://www.allcarselectric.com/blog/1044806_2011-chevy-volt-to-offer-mountain-mode-for-hill-climbing#) performance "may be degraded" under sustained heavy loads when the engine providing electric power to drive the car. The Mountain Mode option helps compensate for this in some circumstances. While drivers may not be used to planning ahead, future navigation systems might suggest that the special mode be triggered if it knew that a preset route included a long uphill stretch.