Last post on Aug 25, 2008 at 12:05 AM
You are in the Hybrid Vehicles - Archived Discussions
This discussion is ARCHIVED. To reactivate the discussion, post a request in the Lost? Ask the Hybrids Host for directions! discussion.
What is this discussion about?
Engine, Fuel System, Transmission, Hybrid Cars, Coupe, Convertible, Hatchback, Truck, Sedan, SUV
#167 of 206 Re: Battery Regen Worthwhile ? [dhanley]
Nov 03, 2006 (10:04 am)
My calculations on ultracapacitors, perhaps not including the latest components, showed they have an effective power density the same as NiMH batteries which makes them just as heavy.
Power density is the most important parameter to Toyota.
The earlier model of Prius had 38 7.2v cellpacks of 800w/kg power capability. When the the newer Prismatic cells became available with 1300w/kg they were able to trim the number of cell packs down to 28, at least that is my take.
Since both types of cellpacks weighed in around 1050 gms, and both had energy storage of 46Wh/kg this meant the lighter '03 battery also stored less energy, but its ampacity was much greater which was the major interest to Toyota. On paper this computes to 180 amps, up from 110amp. In practice a maximum of 100 amps seems to be used.
I was just on the Maxwell.com Ultracap site browsing their interesting products with 10Kw/kg power densities but they didn't give the weight of their 650F 2.7v , for example, so I couldn't compute how many amps they could deliver. Of course if it weighed 1kg then 4000amps, but then what is the ESR ? I am not sure I trust their 10kw/kg figure just yet - they are holding too much back. A scalability issue perhaps.
see yhoo prius_stuff #1071,#1165 and #17142 for ultras and regen they could be useful posts, but posts like #1068 refer to the earlier Prius which I think we should keep out of Edmunds to deal with the latest technology here. Also they are not so warm to non owners cluttering their site with speculative postings, these days. Never mind that talk of plunking down $12000 for an EEstor Li-ion, doesn't seem to phase them at all! Buying a Prius is on my horizon but I want the 'right' technology. Small engine, lightweight and no HV battery. In a few words my Prius has to be quick, simple and cheap. A pure series hybrid. I see the HSD as heavy and complicated right now. And rather expensive too I might add.
#168 of 206 Re: [gagrice]
Nov 03, 2006 (6:07 pm)
Lets expand on the engine stop question. A diesel engine is torque heavy. It doesn't relie on horse power. If you allow the engine to operate at a low enough rpm to keep the needed compression to ignite the fuel you can store the excess energy produced as stored energy in the form of compressed hydraulic fluid in the high pressure accumulator. You can also valve the engine to allow the pistons to move under no load until engine power is needed again after the stored fluid energy has been depleted. Diesel engines need heat of compression to ignite the fuel. It is not the re starting of the engine as much as getting the engine up to operating temperature which gives rise to the poor fuel saving with shutting off the diesel engine. Also storing energy in the form of a high pressure fluid gives specific power from 3kw/kg to 7kw/kg at a much lower cost then batteries available today.
#169 of 206 NOx due to combustion temp
Nov 03, 2006 (6:44 pm)
I forgot. If you can lower the compression of a diesel engine you won't burn your fuel as completely. So with the CRD engine by increasing the injection pressures and lowering the amount you get much better distribution of fuel into the cylinder to make up for the lower compression which compensates somewhat with the incomplete burn. This also lowers the NOx output. (Combustion at lower temperatures) They are very close to balancing the compression with the fuel burn issue to lowering the NOx output of the diesel engine without after engine treatments.
#170 of 206 Re: Battery Regen Worthwhile ? [tpe]
Nov 09, 2006 (6:17 am)
I just visited Altair nano's site and saw that the power density of the nanosafe cell is qoted at 4000w/Kg which is three times that of the Prius NiMH. But though the theoretical limit is 180 amps for the Panasonic cell I see that Toyota doesn't risk more than a 50 amp charge (sic) and 100 amp discharge (via scanner).
For the nano cell if we choose a more conservative 2000W/Kg that would infer about a 300 amp charge which would get you a regenerative stop of 60mph to rest in roughly 8 seconds. More interesting just 25kg could provide 50kw for acceleration which should definitely impact engine size needed. Right now, if I may remind you, Prius has 28Hp/76Hp battery/ICE ratio. Toyota doesn't have a smaller engine than the 1.5litre which would work well with this powerful a battery.
As other posters have observed the car companies aren't seeming to follow this mantra, we'll all just be sitting ducks when the next spike in oil price occurs. The Prius is going to maintain its sales but I believe there is interest in a vehicle size below that. This battery could certainly change the dynamic if it became available.
The fast plug-in charge of a 100Wh/Kg battery at the 2000w/Kg level would take 100*3600/2000 or 180 secs with a 50kw supply for 25Kg. For BEV enthusiasts the best charger for this system would probably be another nano battery on permanent trickle charge.
I did notice Altair included footnotes regarding "forwardlooking statements" - Safe Harbour language.
#171 of 206 Re: Battery Regen Worthwhile ? [toyolla2]
Nov 09, 2006 (12:12 pm)
This battery could certainly change the dynamic if it became available.
This battery is available, somewhat. Altairnano has a $750,000 order for their battery packs from Phoenix Motorcars. They've already delivered at least one 35 kWh pack and its installed in an SUV that's currently making the rounds at the alternative energy shows. My understanding is they are contracted to deliver 10 of these packs by year end. Not exactly high volume. Some company with a lot of manufacturing capacity needs to pay Altairnano a licensing fee and start churning these things out.
#172 of 206 Re: Battery Regen Worthwhile ? [tpe]
Nov 10, 2006 (10:50 am)
"100 lbs still seems like a lot of weight for a 1.3 kWh battery pack"
You mean compared to the 72Ahr battery in your car ?
But that oldtech commodity battery weighs but 50lbs and holds just 0.9 kwh and costs a hundred dollars.
Why, if you made one twice as heavy it'd store 1.8 kwh and set you back a whopping two hundred bucks.
Why on earth would you do that when for $2000+ you could pick up one of those hi fallutin' NiMHs with 1.3 kwh ?
Don't take me seriously. It's Friday.
I'm just fooling around, that's all !
#173 of 206 Re: Battery Regen Worthwhile ? [toyolla2]
Nov 10, 2006 (2:41 pm)
I think we're in agreement here.
On one of your previous posts you gave the altairnano battery 2000W/kg. I think that their claimed 4000W/kg has been demonstrated so you can go with that. This type of technology allows for a stupidly fast series hybrid that has no more than a 80 kg battery pack. There's guys like Richard Branson, founder of Virgin Airlines, donating 1 billion dollars to green causes. If I was in his position I would contract to build a high performance series hybrid with the Altairnano battery coupled with a highly efficient diesel generator. I don't think it would be that expensive.
#174 of 206 See this story for more than anyone needs to know about HSD
Mar 09, 2007 (5:26 am)
This is a pretty technical article about the HSD system versus other types of hybrid systems.
Even has MATH equations.....how nerdy !!!
A tale of two hybrids
#175 of 206 Re: See this story for more than anyone needs to know about HSD [larsb]
Mar 09, 2007 (4:11 pm)
larsb, welcome it's great someone in this fading republic has found time to contribute to the technical side of things. We can't complain about our North American domestic manufacturers being systematically dismantled because of the advanced engineering prowess of the Japanese products if we can't even support a scientific technical thread in one of the major automobile web sites, possibly the major automobile website in the USA, here at Edmunds.
Oh, this just in - Magna International, an auto supplier like Delphi but unlike Delphi not in chapter 11, just announced it is looking to partner with three equity firms to takeover Chrysler in order to protect its order book. Didn't waste any time did they ?
Two thirds of their business is with the big three and with $2Bn in cash and $2Bn in reserves, I guess Magna can be a player. They might even pick this time to go after their rival so over at Delphi they better start putting broomhandles in those doors !
The posted article seems to be riddled with inaccuracies, starting with : -
"ICE: Internal Combustion Engine - The standard drivetrain of cars way back in the 20th Century."
History will no doubt recall the ICE as a prime mover.
The standard drivetrain of cars way back in the 20th century would of course include the ICE plus a clutching arrangement controlling a multistage gearbox.
Since the author is going to go on to describe systems which don't have some of those things mention of them should have been included at the get go.
I've learned that it is important to describe the architecture very accurately otherwise you can find yourself inadvertantly making statements that are BS.
Take the Prius, for instance, the writer omitted to point out that the transaxle that delivers power to the differential via two intermediary spindles is only 82% efficient. Account was taken of the losses in the PSD caused mainly by churning electrical power between MG1 and MG2 but what were those 95% transmissions ? I would also like to see those 95% efficient transmissions, sadly not on this planet charlie, a 1:1 ratio might be 95% but anything above 1:3 and you're looking at 93% and that's just for a single mesh.
Also the Power Split Device is actually a torque split device a more knowledgeable writer would have pointed out.
However the writer did conclude that the series hybrid may become the predominant architecture in the future. However I would have to take issue with his description of what a series hybrid is. There is more than one type you know. The writer's version is essentially an EV with a back up generator to provide enough energy to cruise. Let's say at 70mph, about 20Hp I suppose.
An entirely different direction which I have been refining over the past thirty years not including a couple of concentrated years on the internet suggests a unique version which rarely gets mention. In this version the battery and ICE roles are reversed. The prime mover would now be a powerful but small engine (600cc or less) driving a hi-speed generator at up to 12,000rpm when 100kw or 120Hp is needed for those short periods of extreme acceleration. This version would have no high voltage 'boutique' energy pack of expensive dubious chemistry either. The keynotes for this idea being simplicity, low mass and cost.
For replacement of the HV battery the existing 12v lead acid would be just slightly beefed up and equipped with a step up converter in order to perform the 'virtual HV battery' role. This would facilitate engine starting via the generator's feed_thru inverter and at other times allow low speed "electric only" operations to 10mph. 10mph since a single general purpose battery would not have the power capability to put out more than 1500W on a continuous basis.
#176 of 206 My brain dump...
Mar 23, 2007 (4:10 am)
Edit: I see now that the previous post to mine by toyolla2 talks about exactly this same idea, I apologise if my post reads like this is my original idea, it was you who first mentioned this idea to me...
I will try and post a sane distillation of whats in my head!
....whilst I catch up on what Ive missed since my last visit here!
I know the major thing holding back all electric vehicles per se is battery technology, we can't get enough juice for the given size/weight to make an electric car go the distance we would want out of a family car (about 350 miles on a tank) I also know that even the latest li-poly batteries are prohibitively expensive, still take a while to charge and suffer from charge loss over time, ie they have some way to go before we reach the holy grail of a lossless, high concentration electrical energy store...
I also know that if we all made a slight change in our driving habits and if our workplaces would provide sockets for charging your car whilst at work and our respective governments help put in place the infastructure for charging your car at home(I live in an appartment without a garage, so running an extension cord out to the car would get me loads of more headache! ) we could all live with and love the current best of breed electric cars (tesla roadster is an example of the right technology, but, too expensive for most of us)
That said I also think a better more gradual change involves, hybrid cars that still run on petrol, but, eek out the most efficiency out of the fossil fuel and as a by product lower emissions drastically. Which brings me to the meat of my post, Ive posted some of this here before, but talked about a diesel engine powering a generator that charges an onboard battery and drives an electric motor that drives the wheels (a serial hybrid). I realise that by adding the conversion from fossil fuel to electricity and storing most if it in lossy battery then converting it back to motive power to the wheels involves quite a few losses of efficiency.
Ive been thinking about something said to me a while back be either toyolla2 or goodcrd ???, sorry folks if I've got this wrong it was a while back. It was essentially that of whther we need a large battery store at all!?
In essence the gasoline engine powers a generator that drives an electric motor directly... Lets talk efficency of such a setup, how much energy loss are we talking here?
Im going to make some assumptions here: (these is just guess work)
Typical motor electricity to motive power efficiency: 85-90%
Typical generator motive to electricity efficiency: 80-90%
So a simple scenario where we replace the drive train (gearbox, clutch, drive shafts) with a generator coupled directly to our gasonline engine, which then powers a motor driving the wheels, would net us a lower estimate of about 68% of the engine output (85% * 80%).
With the original clutch/gearbox in place I know you lose some of the engine power too, what is this roughly, about 10-15%? Would this electric drivetrain be any lighter than the equivalent mechanical drive train(gearbox, clutch) I know drive shafts would be needed for the electric motor too, but with in wheel motors being talked about this too might not be needed!
How much loss in efficiency in using this electric drive train are we a talking about over the mechanical drive train? My of the top of the head guess would put it about 20%.
Now couldnt this be efficiency loss be made up in using a smaller lighter gasoline engine (3 cylinder, lean burn, 1-1.5 litre capacity if not smaller like a motorbike engine!) that has been tuned to run at a high rpm with turbo charging if necassary (would this be even needed!)?
Wouldnt focusing on a smaller lighter more efficient gasoline engine be the way to go. It wouldnt need to provide a wide power band, just a very small highly efficient band of power producing electricity to power the motor. (you could even include some ultracapicators that could soak up the excess electricity produced if the car is moving too slowly for amount of electrical power the gasoline engine/generator combo is producing and if you were to use regenarative braking, this could then be used to provide extra power to the motor when needed, or when restarting the gasoline engine if its been shutdown)
Another benefit over a standard ICE mechanical drive train setup would be the internal passenger cabin layout options provided by the space saving of not having a large engine/gearbox, drive shafts/tunnel to the rear wheels.
Sorry that this post is long, but, Im fascinated by all of this, should have been an engineer instead of the desk bound computer programmer that I am !!!!
Any ideas, criticism is welcome as is any kind soul that can point out any huge holes in my understanding or concept.
Its all gone very quiet on this board of late!