Why no liquid fuel capacity for EVs? - Fuelly Forums

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Old 09-12-2006, 02:22 AM   #1
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Why no liquid fuel capacity for EVs?

It seems that most, if not all electric car builders/manufacturers shun the notion of the ICE, even though an electric vehicle with a large enough pack for most daily use, and a small, appropriately sized gasoline generator for long trips, would exhibit all the efficiency, reliability, and instantaneous power of an EV, with all the range that liquid fuels provide. All while minimizing what seems to be the most costly component, batteries.

The electricity bill to run a vehicle exactly the same size as whatever we drive now would be ~a third of what our current gasoline bills is, and the gasoline cost would drop by ~40% because we would be eliminating the majority of inefficient gasoline engine operation... Unless of course we pulse and glide. But the whole point is that it would open up ~P&G mpg for everyone w/o all the hassle.

Even at homebuilt prices, I bet these would be competative with pure EVs and ICE powered vehicles... They would initially cost a little bit more than ICE vehicles due to lack of volume and battery cost, but as production ramped up, they eventually end up being cheaper than most ICE versions due to the high cost of the modern drivetrain/emissions system, while offering a ~40-75% reduction in fuel costs, better acceleration, fewer repair costs, and longer vehicle life.

While I can understand that most manufacturers can't instantaneously alter their production, they have contracts with suppliers and whatnot, if we don't start seeing 100mpg vettes and 200mpg corollas in the next few years, I'm gonna be mad. And write an email to someone. maybe not...
But anyway, with gas at $1 a gallon, the electrified drivetrain is more or less equivalent in cost, but now that we've been holding steady at $2-3 for the last few years, there's no reason for manufacturers not to start rolling out fuel efficient, high performance, long range, economic vehicles.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 09-12-2006, 04:16 AM   #2
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Build it and they will sell. A small high quality honda motor of a few HP on a generator still only burns gas at 25% efficiency then add the losses in generating and charging then battery losses and it become a pretty lossy system plus it adds weight to the vehicle - so it becomes something to avoid.
Now a parallel hybrid is something else and is what eCycle is working on so that any combination of ice and electric can be used.
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Old 09-12-2006, 05:54 AM   #3
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Can you lend me a few million dollars?
Most small Honda engines seem to be in the ~310g/kwh, and supposedly the average minimum BSFC for a car is ~250-300g/kwh (Prius at 225g/kwh), with the average being somewhere around 500-600+g/kwh, even with the Prius. A small diesel engine has even better consumption numbers with ~260g/kwh. So right now we're at ~60-100% better mpg depending on ICE engine type. Of course, we need to convert that mechanical power to electricity, but there's no reason to charge the batteries in order to power the electric motor when we can just go straight to the electric motor, with the battery pack acting as a buffer, and any extra electricity that's generated charging the battery pack to a certain point if it's discharged.

Like you stated, with a small high quality Honda genset, like the EU2000i which costs ~$500/kwh and weighs ~30lbs/kwh, the efficiency is still roughly ~400-450g/kwh, and even if it goes directly to the electric motor at 80% efficiency, we might as well have a normal gasoline engine. But, even though the engine is pretty fuel efficient as small gasoline engines go, the conversion is only ~60% efficient, so it's very inefficient at turning gas into electricity.

Otoh, there are some very efficient, but pricier, diesel (and I'm guessing gasoline) gensets that run ~$800/kwh, weigh ~60lbs/kwh, and use ~300g/kwh. The motor efficiency is ~80-90%, so we're at a bit under 335-370g/kwh, or ~35-40% better efficiency than the average gasoline car gets. Of course, these are off the shelf items that aren't designed for automotive use and don't have the advantage of mass production that parts used in autos do.

For example, lets say the average small car needs ~8kwh to go an hour through the EPA highway cycle, so we'd need a ~$6k genset. But GM makes small cars that sell for $9k. Is the genset really that much more expensive? I doubt it. Mass production brings the price of stuff way, way down, and since these generators aren't mass produced like an auto manufacturer's parts supplier can, they're expensive so the company can sell very few and still make a profit.

Anyway, there's also the electric motor/controller, and there's plenty of info about these. They seem to run in the $3-5k range with low volume sales depending on size, and the batteries, which are where most of the cost comes from, are ~$500/kwh for NiMH and $800/kwh for li-ions. A 50kwh pack of li-ions, enough to take the Tesla Roadster roughly 250 miles runs $40k. Otoh, an 80 mile range only needs ~$13k worth of li-ions, or $8k worth of NiMH or NiCD batts. So there is a lot of money that can be saved by using a small efficient $6k genset instead of $27k worth of batteries. The majority of day to day driving would be using only electricity, and long highway trips could use the genset at some fixed speed, with ~35-40% better mpg. Even more if the size is smaller so that people have to drive 55mph.

At most, an aerodynamic Aveo with LRR tires built along these lines would be ~$25k using current prices, probably ~$15-20k with mass production. The diesel genset would last an extremely long time due to minimal/extended use, the electric motor is practically bulletproof, and the batteries should last ~50-100k miles depending on type. When the batteries need to be replaced a five to ten years down the road, the price will probably be substantially less, and considering that the cost of oil probably won't go down anytime soon, I think they'd be great for the consumer.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 09-12-2006, 07:07 AM   #4
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Put a ICE in a car and you have to pass emmissions testing and crash testing unless you are converting an existing car. The Li-Ion battery made from laptop cells have other design considerations namely that you have to have enough to provide the watts so that you really can't use too many less or else you will not have the voltage and current that is required. The cells only put out about 3.8 volts at 2-3 amps each under load with a good charge in them. If you do the math on the power requirements you find that the more cells you have the more power you can generate and the longer they will last. When all is said and done it ends up costing a lot more than you think. Now $3k on a small battery pack of Li-Ion cells for a motorcycle size electric conversion makes a lot more sense.
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Old 09-12-2006, 07:21 AM   #5
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I don't buy the cells argument you make. We're talking something that pulls down ~250hp and only needs a 50kwh pack, 50electric hp would be equivalent to what an Aveo currently uses, and probably only need the same proportion of instantaneous power, I'm guessing 8kwh (o.k. maybe 10kwh) would be acceptable considering how the aveo accelerates currently. I was assuming we went with NiMH or NiCD and sacrificed some weight for the $4k price tag, or we could go with something like $7k with li-ion.

We could add additional batteries for more range/instantaneous power, and by the time we've hit $40k we'll probably have corvette performance with much more electric range. But then we wouldn't be at the same price point.

As for the comment about requiring crash testing with a small ICE. I'd love to see some info as I'm not picking up anything off of google. I've seen something about how the EPA calculates equivalent fuel economy for an electric vehicle, and they mention if there is any power coming from an ICE then the conversion factor is different, but they still classify it as an electric. I'm thinking that maybe there's some power or displacement limitations. Alternatively, this could be built smaller/light/with three wheels in order to bypass emissions/crash testing as a motorcycle in some states, with better fuel economy and quicker acceleration as a byproduct. The Aveo shell was just to compare the price of something that's currently used.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 09-12-2006, 09:49 AM   #6
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A typical 18650 Li-Ion cell max is 5 amps at 2ah is 6wh of energy so if you need 50hp = 38kw of power = at 10 watts per cell 3a x 3.6v ... 3800 cells * $3.70 = $14,060 = 22.8kwh battery = 159.6 volts at 200ah (Peak charge voltage in 38s x 100p configuration). These are real number from measurements and purchases I have made of some good cost effective cells. Higher output cells are available but would have simular ah ratings and cost several times more per cell. At a typical car energy use of 5 miles per KWH you would have 114 mile range. At 500 cycles you would have a life of 57,000 miles.
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Old 09-12-2006, 10:29 AM   #7
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Huh, I never knew 18650s couldn't provide that much power... I was thinking of 1.2V 10ah NiMHs, which according to the manufacturer, can be pushed to 30ah continuously, and 50ah for short periods of time. At 1.2v(50ah)=60w, for 38kw of power I'd need ~650 cells, which would be ~$3,500. At the 30ah rate the pack would be ~$6k. At 5mile/kwh the pack would take me ~40 miles assuming 10ah, however, an Insight is roughly 10mile/kwh, and I figure an Aveo with similar CdA/Crr could be done, so ~80 miles in that case. The 100k mile was for ovonics NiCDs, which supposedly can clock 1000+ cycles at 80% DoD.

According to your calcs the Tesla Roadster must be pulling ~12amps to generate 250hp=185kw peak power from a ~55kwh pack. How are they able to pull so much more max current? Assuming I didn't bork the calcs someplace.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 09-12-2006, 01:39 PM   #8
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First a 1.2volt NiMh will drop to about 1.0 volts at 50 amps (don't mix ah - Amp Hours with A - Amps). I have some 12ah "F" cells that are good for 50 amps continous and I have run them at that power level so you get 50 watts. Now you want 250hp = 190,000 watts = 3800 cells but you end up with maybe 10ah or about 10-12wh per cell at a cost of about $8 per cell = $34,000 plus you have to balance them like crazy because they self discharge so much and you also have to put 20-50% more kwh into them to fully charge them and they will get hot if you fully charge them. You really shouldn't put them in parallel when charging and they only produce about 1 volt out at full load, this requires more in series and more balancing circuitry and then the weight is higher also.
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Old 09-12-2006, 03:07 PM   #9
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Oh no, I'm still shooting for the 50hp figure, which should only require ~$7k worth of cells by your estimate. Of course load balancing stuff would be required, but I'm figuring they would only be fully charged overnight, with each series string being charging individually. The "extra" current from the genset, when it's on, would push them to ~80%, or whatever they can be quick charged to. The cells I was looking at were ~$5.50 a cell, and supposedly would run 30a continuous (just replace where I stated ah with a, except for the actual 10ah rating of the battery ) and 50a for short periods of time. So we're talking 50a per cell, or ~700+ cells to make 35kw, which should also provide ~80 miles assuming a insight'ish glider, and cost $4,400 (800 cells at $5.50 per cell) plus tax and S&H.

Personally, I'm probably going to with half that in a small faired trike, but that's a potential pet project, among many. Hopefully I can run ~30hp in a 400lb vehicle, or the equivalent of 150hp electric motor per ton.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 09-12-2006, 04:03 PM   #10
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Yup a trike would be the way to go and hide the motor and batteries and keep the pedals functional. You will not need 30hp unless you want to go really really fast. I still don't like using NiMh cells that much - have a bunch of them and they are a pain to keep charged properly - they can go dead in a week just sitting with nothing connected to them where as Lithium will stay charged for months.
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