Performance Electric cars

[Ian Rogers]

Sounds like you have not given up your grudge yet tvtech?

If you and mickster want to step into the ring and go few rounds with me just let EM know and I will be happy to oblige the both of you otherwise I suggest leaving the nasty little critters sleep. A lot more went on behind closed doors than either of you are aware of.

Leave it in the past!!!! First of all, Its off topic so I don't think its necessary!!! Secondly..... Well there is no "Secondary".... Just move on.....

I had an irritating little pest of an animal that refused to go away. No matter how many times it was thumped on the head.
It irritated everyone because it thought it was clever. And bit people all the time. Nasty, vindictive little critter.

It got to the stage where I could not even give it away.

One morning....all on it's own, it left. I felt sad for it as it simply went away. I never found it again and never even really bothered to look for it.

I felt sorry for it that it did not even bother to bite the hand that fed it.

It just went away and never bothered with even a bite. It probably realized it had screwed up and decided to go away.

Sad story. I know humans like that too.

 

[ronv]

How do the hydraulics make it any more efficient than just an engine transmission and differential? Or a DC motor and a differential? I can see the hydraulics where you need huge torques and I guess automatic transmissions are hydraulic, but.....
My taxes on gas are 37 cents. At a million a mile to build roads anymore I don't guess that's to bad compared to the price of gas which is also cheap here (by comparison) at $3. I think I pay only 11 cents for my electricity taxes and all. Nowhere near 50 cents.
If it were up to me, and I suppose everyone is glad it isn't, I would try to make sure the last drop of oil at the end was in the US.

 

[ronv]

The Tesla is a thing of beauty and it seems simple enough to me. Some batteries (fancy lithium) a brushless motor a gear reducer (14,000 rpm to wheel speed) a igbt controller and I'm sure some micros to optimize regen etc.
88% efficiency, eight year or 125,000 mile warrantee on the batteries and best of all 0 to 60 in less than 4 seconds.
I see now where they are talking of battery swap stations to eliminate the charge time problem. Not sure if they will pull that off, but maybe.
They have a problem getting the volume up to get the price down. I think if I were them I would try to do a deal with a manufacture. Bet the price could be cut in half. But maybe they are doing it more for fun than profit.
Or like tc says, they could make it half as fast and pull a few buck out of the motor. But I think they had to make it fast to sell it over the drawbacks.

The fuel cell are neat, but suffer the same range problem and you have to convert electricity to hydrogen which I think is pricey. Then there is the infrastructure problem.

 

[rc3po]

Keep in mind how long it took for cars to become as reliable as they are now. In the old days, cars were much simpler, but still not all that reliable. With modern approaches, even very complex systems can be made reliable, but it takes time on the engineering side to work out problems that are found on the road.

We haven't mentioned it here, but the real problem is not so much the battery capacity, but the time it takes to charge the batteries. If you could charge the batteries in a few minutes (comparable to filling a gas tank), the lower range would not be a big issue because you just need to stop more often to "fill up". But, batteries take hours to charge from a socket, which is why I think an internal combustion engine is a good thing to have for continuous charging for long trips. Perhaps another solution is to have removable battery modules. Then instead of going to the station to fill up gas, you go there to swap your batteries. Companies could charge for the rental of batteries and for the energy used. The car owner would not even need to get the batteries when he purchases the car.

Anyway, we are starting the process of a major evolutionary change in automobile design and it is not all that clear exactly where we may end up. Also, I think it is strange that someone like myself, who does not know all that much about car design, and the mechanical engineering side of automobiles, may be somewhat of an expert on car technology once this evolutionary step is complete.

You don't need an engine to turn a generator to charge the batteries. You could maybe have small hydraulic pumps turned by the wheel axles to power the generators. No need for gasoline at all.

 

[steveB]

No need for gasoline at all.

My point was not that you necessarily need the gasoline, but only that it is a desirable feature to have a gas engine available to charge the batteries for long trips. Think about it. If you don't have available battery swap stations, then an all electric car can not make long trips very fast. The range is not all that impressive and once you are out of charge you have to wait several hours to recharge. This isn't practical for all people.

 

[tcmtech]

You don't need an engine to turn a generator to charge the batteries. You could maybe have small hydraulic pumps turned by the wheel axles to power the generators. No need for gasoline at all.

And where exactly does the energy to turn those wheels come from to begin with?

Think about it.

 

[tcmtech]

How do the hydraulics make it any more efficient than just an engine transmission and differential? Or a DC motor and a differential? I can see the hydraulics where you need huge torques and I guess automatic transmissions are hydraulic, but.....

Hydrostatic drive systems variable displacement pumps and motors are a efficient way of creating a means to produce very wide gear ratios for either high torque or high speed with a smooth change from one end of the operating range to the other.

Contrary to popular belief in practical application a efficient electric motor does not produce the same mechanical power over its full operating range. 100% torque at zero RPM's is still zero power. Quick acceleration requires high initial torque from the wheels that rapidly changes to higher speeds with less torque but the total energy being transferred is still the same.

To get high torque at low RPM's from an electric motor either requires a large motor with a lower top end speed or a smaller high speed motor with a gear reduction. Using variable displacement hydrostatic pump and motor systems between the primary electric motor and wheels would simply allow for the electric motor to run at its maximum mechanical power point while providing continuously variable gear ratio transmission system between the motor and wheels.

Hydrostatics are not a magic bullet for making more energy from nothing. All they are is a way to produce highly variable and wide ranging gear ratio transmission with a high power to weight and mass ratio.

 

[rc3po]

My point was not that you necessarily need the gasoline, but only that it is a desirable feature to have a gas engine available to charge the batteries for long trips. Think about it. If you don't have available battery swap stations, then an all electric car can not make long trips very fast. The range is not all that impressive and once you are out of charge you have to wait several hours to recharge. This isn't practical for all people.

I agree. What I'm saying is that they need to think of ways to charge the batteries while the vehicle is moving. You could use a pneumatic pump to turn the generators also instead of hydraulic pumps. A small pump could turn a generator easily. But they want to make money from people buying electricity. They are all so greedy!

 

[steveB]

I agree. What I'm saying is that they need to think of ways to charge the batteries while the vehicle is moving. You could use a pneumatic pump to turn the generators also instead of hydraulic pumps. A small pump could turn a generator easily. But they want to make money from people buying electricity. They are all so greedy!

I'm not sure I'm following your point. It's not clear how you avoid buying electricity with an electric car. Greed (which always exists) aside, there are some nice long term benefits possible with electric power. Although we are not fully there yet, much electricity comes from hydro-plants, and the future should see use of more renewable energy such as solar, wind and ocean power. This means that a higher percentage of non-carbon energy would be used. This is a long term concept and it will be a while before it really makes full sense, but the technology evolution takes time anyway.

If you are just talking about more efficient use of energy by using regenerated energy while driving, then I agree with you that recharging is important, but this concept is already in effect. The nice thing about electric motors is that they naturally can be run in reverse as electric generators. Also, inverters can be run in reverse as rectifiers. Hence, recapturing mechanical energy and recharging batteries is straightforward and is done. However, one problem is that the rate that the energy comes back is very high, and can be greater than the charging rate for the batteries, which again the charge rate of the batteries is the real obstacle here. One solution here is to have capacitors along with the batteries. The capacitors won't have the capacity of the batteries but can take a limited capacity back at a high rate. The capacitor energy can then be used for high power load situations, or for gradually recharging the batteries at the lower rate allowed.

 

[tcmtech]

What I'm saying is that they need to think of ways to charge the batteries while the vehicle is moving. You could use a pneumatic pump to turn the generators also instead of hydraulic pumps. A small pump could turn a generator easily.

And once again where exactly is the energy coming from to drive the compressors or pumps that turn the generator?

 

[rc3po]

I'm not sure I'm following your point. It's not clear how you avoid buying electricity with an electric car. Greed (which always exists) aside, there are some nice long term benefits possible with electric power. Although we are not fully there yet, much electricity comes from hydro-plants, and the future should see use of more renewable energy such as solar, wind and ocean power. This means that a higher percentage of non-carbon energy would be used. This is a long term concept and it will be a while before it really makes full sense, but the technology evolution takes time anyway.

If you are just talking about more efficient use of energy by using regenerated energy while driving, then I agree with you that recharging is important, but this concept is already in effect. The nice thing about electric motors is that they naturally can be run in reverse as electric generators. Also, inverters can be run in reverse as rectifiers. Hence, recapturing mechanical energy and recharging batteries is straightforward and is done. However, one problem is that the rate that the energy comes back is very high, and can be greater than the charging rate for the batteries, which again the charge rate of the batteries is the real obstacle here. One solution here is to have capacitors along with the batteries. The capacitors won't have the capacity of the batteries but can take a limited capacity back at a high rate. The capacitor energy can then be used for high power load situations, or for gradually recharging the batteries at the lower rate allowed.

Yes, that's what I mean - systems to use to charge the batteries while the vehicle is moving. Even if they can't keep the batteries fully charged even while you are driving, they could at least increase the range of the vehicle between plug-in charging.
If the range of an electric car was 600-800 miles, it would be much more appealing to consumers. Hotels could have charging stations for customers.

 

[rc3po]

And once again where exactly is the energy coming from to drive the compressors or pumps that turn the generator?

The wheels. As they turn, they drive the pumps. The pumps are kept at the needed pressure by it's internal pressure regulator. You could also have accumulators so that even in stop-go traffic, you still get some charging.

 

[tcmtech]

Seriously? ? ???????????

Where is the energy turning the wheels coming from?

Think the transfer of energies through full circle once and show your math.

I am curious as to where you think this is going to improve things.

 

[rc3po]

Seriously? ? ???????????

Where is the energy turning the wheels coming from?

Think the transfer of energies through full circle once and show your math.

I am curious as to where you think this is going to improve things.

Axles, if the wheels have them. If not, then off the spindles. When the wheels turn, so do they.

 

[tcmtech]

Let me clarify. Where is the power that is turning the wheels ultimately coming from?

 

[rc3po]

Let me clarify. Where is the power that is turning the wheels ultimately coming from?

Are you kidding, or just messing with me?

 

[steveB]

I assume rc3po is talking about recapturing energy during breaking or in downhill stretches of road. Definitely, that is a targeted goal of these systems. Recapturing as much energy as possible is the way to go. There are limits on efficiency and charge rates, but it makes sense to to the best you can. But again, I'll stress that the electric motors and inverters needed to power the car are well suited to recapture the energy also. If only the batteries could be charged at the same rate that they can discharge, we would be in much better shape then.

There are new lithium ion capacitors that can be charged and discharged at very high rates, but the energy density of these devices are only starting to approach that of lead-acid batteries and can't compete with lithium battery energy density.

There is another issue with charging I can mention too. Even if you make a storage system that can be charged quickly (for example a huge bank of lithium ion capacitors), think about how much electric power is needed to quickly charge them. A 400 V system charged at 200 Amps would need 80 kW of power !!! Remember that next time you file up your gas tank. Think about the rate of energy transfer you are getting when you fill your gas tank in 2 minutes !!!

 

[rc3po]

I assume rc3po is talking about recapturing energy during breaking or in downhill stretches of road. Definitely, that is a targeted goal of these systems. Recapturing as much energy as possible is the way to go. There are limits on efficiency and charge rates, but it makes sense to to the best you can. But again, I'll stress that the electric motors and inverters needed to power the car are well suited to recapture the energy also. If only the batteries could be charged at the same rate that they can discharge, we would be in much better shape then.

There are new lithium ion capacitors that can be charged and discharged at very high rates, but the energy density of these devices are only starting to approach that of lead-acid batteries and can't compete with lithium battery energy density.

There is another issue with charging I can mention too. Even if you make a storage system that can be charged quickly (for example a huge bank of lithium ion capacitors), think about how much electric power is needed to quickly charge them. A 400 V system charged at 200 Amps would need 80 kW of power !!! Remember that next time you file up your gas tank. Think about the rate of energy transfer you are getting when you fill your gas tank in 2 minutes !!!

In any event, I'm sure that electric cars are the future.

 

[steveB]

In any event, I'm sure that electric cars are the future.

Yes, I'm pretty sure about that too. Perhaps some of the details remain to be seen, but it's hard to argue against this.

 

[tcmtech]

I assume rc3po is talking about recapturing energy during breaking or in downhill stretches of road.

I don't know for sure either but given this.

Yes, that's what I mean - systems to use to charge the batteries while the vehicle is moving. Even if they can't keep the batteries fully charged even while you are driving, they could at least increase the range of the vehicle between plug-in charging.

,

I have my doubts he is talking about regenerative braking which in itself is easily accomplished with the drive motors and no extra mechanical systems are needed.

My interpretation is that he is suggesting using the power from the wheels to drive additional generators to recharge the batteries from the vehicle driving itself down the road on the power coming from its own batteries.

That or this is embarrassingly weak attempt on his part at trolling me.