[kennyb]

A plug in hybrid would allow you to use mostly electricity on short trips. Say for under 50 miles.

Then you could plug it in at night.

Only about 20% (I think) of gas energy hits the wheels. Gas is 36kwh per gallon. So in 30 miles, a 30mpg car has spent 7.2kwh of energy. A much greater % of electric energy hits the wheels. Probably close to 100%.

If Toyota could get a car with 10kwh of storage that would be enough for about 50 miles or so. You'd have to be able to program it somewhat, so that he engine didn't turn on and try to top off the battery all the time, as it does now.

Right now Prius has about a 2kwh battery and it weighs 100 pounds. So batteries would have to become more energy dense. I think Prius is 45wh/kg. You'd need about 100wh/kg. Then using 100kg of batteries (220 pounds) it would be an electric car on short trips and a gasoline one on long trips.

This could really help the US kick the oil dependency habit as most trips are 50 miles or less round trip. You could even possibly charge it in parking garages eventually. Electricity is very cheap at 10c/kwh retail.

Does anyone know if they have one in the works or have one in Japan?

 

[artman67]

I think this is the way to go

<opinion>
People will buy the car because it gets good gas mileage
and if they want great gas milage they can plug it in at night

But if they forget to plug it in one night they are not stranded

Then people will install solar pannels .... but hey one step at a time

I went looking for a electric car before I bought my prius and only found conversion kits

I think pure electric cars is to much of a change for people

</opinion>

Site that wants to convert the current prius to a plugin
http://www.calcars.org

 

[BIF]

Hmmm, I don't want to sound pessimistic here, but after careful consideration...

I don't think people who live in apartments and/or make heavy use of their A/C would be able to make much use of a plug-in car.

I find it difficult to imagine people being willing to snake extension cords out to their cars overnight, running the risk of vandalism, lawn-service mishaps, morning forgetfullness, battling the automated sprinklers, or worst of all, defending themselves against lawsuits from parents of inquisitive neighbor-kids.

Plus, using the A/C or driving at highway speeds (when wind resistance will become very high) for just a few minutes would drain that super-dense battery far more quickly than you could go the full range.

It might be a different story if the car can be quick-charged in 30-60 minutes, and not require an actual overnight (several hours) charging time. Then maybe one could justify plugging it in while cooking dinner, paying the bills, or feeding the dog.

I dunno...maybe the engineers here can tell us all that I'm just full of it, and that your idea is doable? <hoping so>

 

[Guest]

Alot of people don't live in apartments. But yes, for them it would be difficult. Maybe parking garages and such could have outlets.

AC doesn't use that much electricity. Maybe a couple hundred watts. The car would use about 5kwh-10kwh per hour and the a/c about .2 kwh / hour.

The thing is on most trips you wouldn't have to use your gas engine at all.

But for people in an apartment, it wouldn't work too well.

It would also be cheaper. $1.00 of electricity would take you 40-50 miles. Plus electric rates would be (theoretically should be ) cheaper at night, b/c it's "off peak".

 

[V8Cobrakid]

I think the prius needs solar panels. Mercedes has a solar panel system on there car (it's small, and between the front moonroof and the rear glass roof on certian models. It's designed to run a car cooling system when it's parked. So, Mercedes gets solar power. The prius could do this too. On the plus side, Toyota would have a larger solar panel area due to the absense of a rear sun roof.

 

[artman67]

I think the prius needs solar panels. Mercedes has a solar panel system on there car (it's small, and between the front moonroof and the rear glass roof on certian models. It's designed to run a car cooling system when it's parked. So, Mercedes gets solar power. The prius could do this too. On the plus side, Toyota would have a larger solar panel area due to the absense of a rear sun roof.

Hey they stole my idea ... ok maybe they had it before me

No more leaving the windows cracked on hot days ... makes perfect sense

 

[kennyb]

Regarding solar cells;

Solar would give you about 200 watts/ square meter in the noon day sun. Right now it would cost about $1000. It would generate maybe 1kwh if it were out all day. That's about $30 a year in electricity or about 10 gallons of gas displaced. Given it were outside in the sun all day, every day and could store it's solar energy in the battery.

So I don't think it's such a good idea. But if thin solar ever comes down in price to $50/sq meter then it probably would be.

You still wouldn't get that much energy from it though.

 

[artman67]

Regarding solar cells;

Solar would give you about 200 watts/ square meter in the noon day sun. Right now it would cost about $1000. It would generate maybe 1kwh if it were out all day. That's about $30 a year in electricity or about 10 gallons of gas displaced. Given it were outside in the sun all day, every day and could store it's solar energy in the battery.

So I don't think it's such a good idea. But if thin solar ever comes down in price to $50/sq meter then it probably would be.

You still wouldn't get that much energy from it though.

Its not to charge the battery its to cool the car only so your looking at about $100 or less depending on how much air flow you want


Quote from a 2003 Mercedes Benz E-Class Road Test

If you opt for the Panoramic sun roof, you can then choose a solar powered ventilation system that will keep the interior from turning into an oven when parked in the sun on a hot day. The system includes a series of silicon solar cells mounted under the glass that can power the blower motor. The fan will automatically switch on while the car is parked in order to cool down the interior. This is done without using any energy from the car's battery.

 

[clett]

How far off are the first plug-in hybrids?

No distance at all!

The only thing is.... don’t hold your breath for the manufacturers to start making them just yet – they’re always years behind getting to market what’s technically possible.

BUT having said that, there is no reason why you can’t make a fully functioning plug-in hybrid yourself today. All you need is a Prius, some batteries and a little electrical savvy.

In essence, all that needs to be done is to install a larger battery pack (wired in parallel with the existing pack), a little home-made charging circuitry for the second battery and a very simple modification to include an EV-only mode button (if it is a non-European Prius). Once set up, the existing battery control ECU will observe the existing battery to discharge much more slowly than normal, due to charge coming from the second battery. So, a trip in EV-mode that would, in an unmodified Prius, discharge the battery to zero bars in under 2 miles, could perhaps give an EV range of up to 10 miles, depending on how big the second battery is.

This is all quite simple and easy to do, but of course the REAL question that needs to be asked is whether or not it’s actually financially worth-while doing the conversion (it’s not at the moment). Nevertheless, here are my cost predictions for the two main battery options for those still interested in such a conversion project:

NiMH
The NiMH batteries used in the Prius are made by Panasonic EV, and have an energy density of about 46Wh/kg. If they were available (they aren’t right now because of supply problems at the factory), you’d maybe be able to buy them over the counter at your local Toyota dealer’s parts desk at a cost of about $1,200 per kWh. Assuming that discharge is limited to 60% range of SOC (for longevity purposes), that means a 10 mile plug in range would require 4.2 kWh of electrical storage (assuming 4 miles per kWh energy consumption in EV mode), at a battery cost of $5,000, and weight of 91kg.

Lithium Ion
The two main LiIon choices for the amateur EV builder are thundersky and 18650. Both end up around 140Wh/kg, and can be had in low volume for about $300/kWh. That means the same 10 mile extended EV mode range would cost only $1,250 taking the LiIon option, and add an extra 30kg mass to the car. However, the overall cost of taking this route will also include the cost of making the battery pack discharge voltage compatible with that of the existing NiMH pack. It’s certainly possible, but not nearly as easy as taking the OEM NiMH approach, which really is just as simple as linking it (or as many as you like) in parallel with the existing battery.

So the answer is that the whole plug-in hybrid thing is technically no challenge whatsoever – the only thing holding it back is cost. In fact (here’s my prediction), I reckon that as soon as things get down to about $100/kWh (2-3 years time at this rate, or much sooner if thundersky start increasing production), you can expect companies like coastaletech to offer this conversion as a popular aftermarket accessory for the Prius. And when the price of petrol escalates to about 70% of the cost of running a car, the same companies will begin to offer packs and motors as aftermarket kits for existing non-hybrid cars.

It’s just a matter of time!

 

[Guest]

Well I am glad that it's just a matter of time.

Question though about your prices and what not. I've read (no cite available) that mass produced NiMH are supposed to be $350 per kwh.

Also a gas engine is 20% efficient maximum ( I think). So for a car to go 30 miles and use 1 gallon it is using 36kwh of gas (heating value). One gallon is about 36 kwh. So the energy to wheels value is about 7.2kwh.

So this means an electric car supplying 7.2 kwh should be able to go 30 miles. Maybe more as it's lighter (even a hybrid with a small gas engine should be lighter than large engined car). Anyway how efficient is the energy in battery to wheels? 90%? I'm not sure.

But I would think you'd be getting about 5 miles per kwh in battery. Maybe 4.

What do you think?

 

[Guest]

When I quoted $350/kwh for NiMH, I meant that is the price they can achieve now with mass production. It potentially could get cheaper, of course.

 

[clett]

But I would think you'd be getting about 5 miles per kwh in battery. Maybe 4.

What do you think?

I went with 4 miles per kWhr for my calculations, as this is what current mid-size EVs appear to be getting, though more advanced EVs with bigger batteries or ultracaps are seeing more like 5-6.

The reason I costed for 4.2kWhr and not 2.5kWhr (which is, I now see, the amount you were probably expecting for 10 miles at 4 miles per kWhr), is for longevity purposes. If you have a 2.5kWhr pack and routinely zap it all the way from full capacity to zero charge it will quickly die (in maybe 500 cycles, or only 5,000 miles EV mode commuting).

But put some limits on the allowed SOCs and the cycle life improves drastically. The Prius battery only allows charge and discharge over a range of 60% of it's real capacity. Doing this allows tens of thousands of cycles, and doing the same for the secondary battery should therefore also mean not having to replace it before the car itself dies. So, I costed for 4.2kWhr and not 2.5 (which is 60% of 4.2).

:wink:

 

[clett]

When I quoted $350/kwh for NiMH, I meant that is the price they can achieve now with mass production. It potentially could get cheaper, of course.

When I suggested trying NiMH, I was really thinking about just using extra packs of the same type already in the Prius, which would mean buying them from Toyota. I read recently that the list price of the '04 1.3kWhr pack was something like $1,500, so I went with that to estimate $1,200/kWhr for this option. Find another supplier of equivalent NiMH and I'm sure it would be cheaper. But lithium is still better! :wink:

 

[Guest]

I though that too about NiMH and deep cycling.

According to this battery expert, that's not the case.

> Do all batteries only tolerate so much deep cycling?
>
> I ask because I think the way the NiMH batteries in the Prius work,
> they are never really cycled very far down. Because of this they last
> for years.

NiMH are very good at deep cycling, as are NiCd and Liion.
In fact NiMH and NiCd have to be periodically deeply discharge
to prevent formation of inactive gamma-form of NiOOH in their
cathodes.
Only lead-acid battery likes to be fully charged and stay
fully charged. In fact, it would be a good solution to use
lead-acid as support batttery for hybrids, I guess decision to
use NiMH was more marketing motivated (to appear green) rather then
engineering motivated - NiMHs dont like to be in fully charged
state all the time.

> However if you wanted a plug-in hybrid battery, you'd obviously need
> to cycle it pretty deeply, otherwise you're not getting much use out
> of it. So would these batteries need to be replaced more frequently?
> Given that a 10kwh pack would probably be needed, this could get
> expensive if you had to replace it every few years.

Reason of most battery death has nothing to do with cycling as such-
it is corrosion of current collectors, active material (in case of NiMH)
and reaction with electrolyte in case of Li-ion.
Good cooling system could help longevity for all this batteries,
and use of high compression for Li-ion could reduce main reason
for degradation - internal resistance increase.
Still, there is no battery on the market that could live more then
4 years in case of intensive use.

 

[RSnyder]

Also a gas engine is 20% efficient maximum ( I think).

The Prius Atkinson cycle engine regularly achieves close to 40% efficiency.

 

[Guest]

[/quote]The Prius Atkinson cycle engine regularly achieves close to 40% efficiency.

That's good. I don't know how the Atkinson cycle works. How and why is it so much more efficient?

I was using the 20% figure as a way to figure out how many miles per kwh electric a car should be able to get. A regular car (I think) gets 20% efficiency so of it's 36kwh (heating value) of energy in a gallon of gas only 7.2kwh hits the wheels. So that's about 5 miles per kwh.

 

[Guest]

Looks like I haven't mastered the quote thing yet.

 

[RSnyder]

To learn about the Atkinson Cycle engine, start with Graham's site.

Click on "Understanding your Prius", then "The Internal Combustion Engine".

Then go to the Toyota site for nicer pictures and graphs.

Enjoy.

 

[clett]

I though that too about NiMH and deep cycling.

According to this battery expert, that's not the case.

Deep cycling definitely reduces lifespan of NiMH and LiIon - it's the whole reason Toyota limited the range of SOC on the early Prius to only something like 40% or so. Think about it from a financial point of view - Toyota could have stuck a small battery in to make the Prius at a much lower cost - but they didn't, they put one in more than twice the size needed that could provide the same amount of storage between a narrower range of actual SOC. The only reason they did this was for longevity - the small battery would have died inside a year and the public would have lost faith in the potential of hybrids.

It's also worth pointing out that Honda took the opposite approach with the Insight. They chose to use more or less the same battery as used in the Prius, but chose a smaller one and programmed it to use much deeper cycling (more available charge storage = better mpg). Now look at the difference between the Prius and Insight forums today - there hasn't been one case of a Prius battery giving up yet, while the Insight group are constantly complaining about 'recals' and dead batteries. Same battery, different depth of discharge.

Still, there is no battery on the market that could live more then 4 years in case of intensive use.

But the Prius has been out since 1997?

 

[flare]

Only lead-acid battery likes to be fully charged and stay
fully charged. In fact, it would be a good solution to use
lead-acid as support batttery for hybrids, I guess decision to
use NiMH was more marketing motivated (to appear green) rather then
engineering motivated - NiMHs dont like to be in fully charged
state all the time.

Reason of most battery death has nothing to do with cycling as such-
it is corrosion of current collectors

lead-acid batteries corrode and as the oxidized metal goes to the bottom of the battery case, it either becomes dead or shorts out...
happens over time even if you keep the battery fully charged

now... people claim that the NiMH wont lose capacity like that, and they are recyclable. wiser choice imo