Thread: Batteries in hybrid vehicles

I wonder how batteries in hybrid vehicles used to recuperate energy of braking in
seconds while it take usually hours to recharge any battery?
What is efficiency of this process? :?
How much energy could be theoreticaly recuperated from braking of average passenger car with 100% efficiency?

Originally Posted by Stanley514

I wonder how batteries in hybrid vehicles used to recuperate energy of braking in
seconds while it take usualy hours to recharge any battery?
What is efficiency of this process? :?
How much energy could be theoreticaly recuperated from braking of average passenger car with 100% efficiency?

I never thought of that before myself. It is possible they use large capacitors to help hold the charge.

Good question. Anyone know? That is a large amount of power to ask the batteries to take in at once.

I have strong doubts about supercapacitors 'cause they have way too low energy
density.With 0.02 MJ/Kg you will need to have few hundreds kg supercap to save
some useful energy or otherwise it's not worthy.And in case of accident such supercap will explode with terrible sound and distruction.And don't forget that in electric hybrid you have looses in four places: brake recuperator,energy storage,current converter and electric motor.So common sense tell you that you cannot have fuel economy more than 10% with the best system of that kind.

Originally Posted by Stanley514

I have strong doubts about supercapacitors 'cause they have way too low energy
density.With 0.02 MJ/Kg you will need to have few hundreds kg supercap to save
some useful energy or otherwise it's not worthy.And in case of accident such supercap will explode with terrible sound and distruction.And don't forget that in electric hybrid you have looses in four places: brake recuperator,energy storage,current converter and electric motor.So common sense tell you that you cannot have fuel economy more then 10% with the best system of that kind.
Maybe those hybrids exist only virtually?

Yeah, common sense is often wrong. Electric motor can easily have an efficiency above 90% without trying too hard. Energy storage in a battery is about the same.

The only thing that is holding back the hybrid/electric car is the large mass of the batteries if you want an acceptable autonomy.

I'm not sure what the issues with recuperation are. The amount of energy isn't that much, and it's usually only for a short time, while recharging is for a long time. The reason you can't recharge faster is that the batteries might overheat. Unless there are other measure taken, it might be a problem in the mountains if you drive downhill for a long time, but that's also an issue for regular brakes.
A hybrid car also needs regular breaks, because the regeneration braking is relative to the speed, so you could easily think of a system which detects "overbreaking" and switches completely or partially to the regular breaks. I have no idea whether this is done.

I've read that NEC developed so-called proton-polymer battery.It has energy density as half as lead-acid and could charge
and discharge almost as fast as capacitor.
If it's true, hybrids will gain great boost.I think it would be interesting to try
such type of batteries in conjunction with electrostatic motors.They are much cheaper then copper based motors.
Do you know if electrostatic motors could be good?
But still, hybrids don't seem to me provide sufficient fuel economy.For example
Toyota Corolla consumes 5.6 L/100 km on highway and 7.5 L/100 km in city driving.Only 1/4 difference! And if will capture 80% of energy that makes this difference it will give you just 20% fuel economy.Relatively modest numbers.
Maybe it's better to make some ceramic engine?

As far as I know, electrostatic actuators are mainly used with very small dimensions. It scales down quite well, because the force is inversely proportional to the distance, and you don't need high currents. The problem at macroscale is that you need very high voltages, which has several disadvantages, such as safety issues and the fact that it's easier to generate a high current at low voltage than it is to generate a high voltage with a low current.

Ceramic engines would be nice, but it's nearly impossible to produce them with any accuracy. Some cars already have ceramic valves.

The thing with the Toyota Prius is also that the engine isn't particularly efficient to start with, so using an inefficient engine in a more efficient way isn't going to produce spectacular results.

If you consider just the highway economy of a Prius, and that a hybrid offers no advantage to steady state cruising, you can easily figure out that most of the reasons the car is efficient, isn't even related to the hybrid system. Aerodynamics are the biggest contributor to the Prius' efficiency. Factor in low rolling friction, engine-shut-off during stops and an electronic display that encourage the driver to acheive maximum efficiency.

So even if you improve battery technology, there's a lot to be said in how a car is designed, regardless of hybrid technology.

I think people are in for a rude awakening if they think the internal combustion engine is ever going to go away. Hybrid cars are too expensive, too heavy and don't have a proven track record. Plus, aside from the new Fusion hybrid, all hybrids drive like crap (thank you bread-and-butter Toyota!).

Look out for all cars going on a severe diet in the next ten years. If you were to remove the dichotomy between efficiency and emissions, engines could be WAY more efficient. Smaller, high-compression, direct injection engines with lighter cars will be stronger in the marketplace than hybrids in the future because they will actually be fun to drive!

Smaller, high-compression, direct injection engines with lighter cars will be stronger in the marketplace than hybrids in the future because they will actually be fun to drive!

What do you think about pyroelectric engine? Some researchers promis 50% efficiency and even up to Carnot limit.
http://www.ikhebeenvraag.be/mediasto...harvesting.pdf

I think it could be good a supplement for hybride vehicles.High efficiency and low maintnance.

Originally Posted by Stanley514

Smaller, high-compression, direct injection engines with lighter cars will be stronger in the marketplace than hybrids in the future because they will actually be fun to drive!

What do you think about pyroelectric engine? Some researchers promis 50% efficiency and even up to Carnot limit.
http://www.ikhebeenvraag.be/mediasto...harvesting.pdf

I think it could be good a supplement for hybride vehicles.High efficiency and low maintnance.

I think it has huge potential, but is there anyone developing it for an internal combustion engine? I'm assuming that's what you're talking about. To harvest the wasted heat from an internal combustion engine to power an electric motor?

I think, there is no sense to use pyroelectrics in conjunction with internal combustion engine, because this is exactly why we need pyroelectrics-to eliminate
bulky ICE with lot of moving parts,prone to break and need for oil changes,cooling
system etc.
To increase efficiency of pyroelectric generator you just need to add more pyroelectric films made of PZT, for example, and optimized for specific temperature.It will work like cascade.
Currently, main problem with it,I guess,is power density that pyroelectrics can generate.When it gets too much electric charge, electric breakdown could happen.
I wonder, if they could use best pyroelectrics,such as PZT, in conjunction with best dielectrics, such as Barium Titanate,to hold as much charge as possible.Or maybe some other solution.