Lithium batteries and smart alternators

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Originally Posted by TB

The entire point of "smart" alternators, the reason they were invented, is to improve fuel economy by using the alternator to capture unwanted kinetic energy in electrical form during **engine braking**.

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TB you have no idea what you are talking about.

I is NOT "unwanted" kinetic energy.

The very concept of charging the battery while the motor is NOT under load, is by using that FREE kinetic energy.

Again, it has absolutely nothing to do with braking.

If the only time you were able to RECHARGE your battery is while you were braking, the little time during a drive that you have your foot on the brake WHILE MOVING, would mean you had no chance what so ever to replace the energy your cranking battery used while starting your motor.

You have read something somewhere and completely misunderstood what you read.

Kinetic energy is not UNWANTED, it is literally free energy and is most definitely wanted, to achieve what they are doing to reduce engine load.

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Originally Posted by drivesafe

TB you have no idea what you are talking about.


I is NOT "unwanted" kinetic energy.


The very concept of charging the battery while the motor is NOT under load, is by using that FREE kinetic energy.


Again, it has absolutely nothing to do with braking.


If the only time you were able to RECHARGE your battery is while you were braking, the little time during a drive that you have your foot on the brake WHILE MOVING, would mean you had no chance what so ever to replace the energy your cranking battery used while starting your motor.


You have read something somewhere and completely misunderstood what you read.


Kinetic energy is not UNWANTED, it is literally free energy and is most definitely wanted, to achieve what they are doing to reduce engine load.

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Well this has taken an unexpected turn. I took some physics in university, and I understand energy better than most people. My career turned out to be IT so I also have a very strong handle on computerised systems. You're making a big claim to say that I don't know what I'm talking about. I'm quite sure there are some things I don't understand, but there's a lot I know in detail. We are probably just miscommunicating on some things.


Kinetic energy might not be what you think it is. It is specifically the energy of moving mass, and to avoid relativistic physics we'll just stick with motion relative to the Earth.
An idling engine does have kinetic energy, because parts are rotating or reciprocating.
But as long as it remains idling, it's not kinetic energy that the alternator is extracting from the system. Here's why:


An engine converts stored chemical energy into heat through combustion.
The heat creates pressure which exerts a force on the piston, and that force does what physics calls "work" by moving the piston some distance.
Work done (J) = force applied (N) times distance moved (m)
Not all the heat does work – some of it escapes by making the engine hot and being transferred to the air via the radiator etc. That energy is basically lost to us.
While in neutral, all of the work done either accelerates the engine itself (temporarily storing energy as kinetic energy in the moving parts) or is also lost, via friction, as heat.
The alternator is connected by the belt to the crank. Through the pistons, conrods, crank and belt, the force exerted by the hot gas in the cylinder is transferred mechanically to the alternator.
Inside the alternator is a magnetic field that's created by a current flowing in the rotor.
Rotating that magnetic field inside the coils creates an electric field within the coils themselves.
The electric field results in current flowing through the vehicle's circuits and doing various kinds of work there.


Chemical energy -> heat and pressure -> mechanical transfer of force -> rotation of magnetic field -> electric field -> electrical energy.


Kinetic energy is not part of that process.


When we engage the transmission the mechanical forces are *transmitted* through the gears and shafts to become a rotational torque in the wheels and then a tangential friction force against the road.
This force does the real work, reacting back through the tyre, wheel, axle and suspension to accelerate the vehicle in the direction you want to go.
Some force is always required to overcome friction losses, so that portion of energy is again lost as heat.
But the driving forces which are greater than friction do work and transfer energy from the heat in the engine into... kinetic energy.
Kinetic energy (J) = mass (kg) times velocity (m/s) squared. If I accelerate my 3,000kg vehicle to 50km/h I have given it 578kJ of kinetic energy.


Now I want to slow down.
I have too much kinetic energy.
What will I do with it?
Well, I can apply the brakes. Brakes use friction to exert a counter-acting force against the motion of the wheel. That force is transferred through the axle, suspension, body etc and even to yourself (you feel it against the steering wheel and seat belt etc) and does *work*. Doing work means transferring energy. What energy?
Kinetic energy is extracted from the vehicle (and the driver's body) and converted to heat energy in the brakes, which again is lost to us.


We got energy from fuel and through the engine and transmission converted it to kinetic energy of the vehicle and its contents so that we could move at 50km/h.
When it's time to slow down, we have some kinetic energy we don't want any more. We have to remove kinetic energy from the system. With brakes our only option is to discard it.


And it's nearly the same thing going down hill. In that case we have a lot of gravitational potential energy (well, *we* don't but the gravitational field between the car and the centre of the earth does) and gravity is doing its thing by converting some of that potential into kinetic energy ie we're getting faster as we roll. Now we can use our brakes to extract that excess kinetic energy from the vehicle and throw it into the air as heat.


Smart alternators (actually it's the computers which are smart, the alternator is just a tool) are used to extract some of that UNWANTED kinetic energy and store it in a form we can later use instead of just losing it. It works just like I posted previously.


I am *not* saying that this is the only time the alternator generates current, or the only reason it does. The car needs electrical power all the time it's operating (and these days even when it's switched "off"). Ultimately all of that electrical energy will be provided by the alternator as it has work done on it by the serpentine belt (force times distance moved just in a circle this time) and that energy is transferred to an electro-magnetic field that causes electrons to move through the circuits in the car. By far the majority of that energy is coming directly from the combustion pushing the pistons turning the crank and driving the belt.


But sometimes the flow of fuel stops. Sometimes the force that's turning the crank isn't coming directly from combustion. Sometimes we're doing *engine braking* where forces coming *from* the wheels through the transmission are doing all the work of compressing air and overcoming friction in the engine etc. AND because the alternator is still on that belt, some of the work done by those forces is to turn the alternator. Kinetic energy from the vehicle becomes electrical energy via the alternator. Come to think of it, in this moment you actually *are* sucking out some of the engine's own kinetic energy too because it's also getting slower.


How much kinetic energy is extracted by the alternator? It depends on the load. The computer knows that if the cranking battery is not full (which it knows because it's been monitoring the current flows in and out of the battery and controlling the alternator voltage so that the battery does *not* get fully charged while cruising) it can increase the alternator voltage causing a current flow into the battery. The battery becomes a load that wasn't there a moment ago. Charging a battery is another form of doing work, of energy conversion. We convert electrical energy into chemical energy.


Let me repeat: when the computer senses engine braking being used it deliberately ups the alternator voltage and extracts some excess kinetic energy from the vehicle's motion and causes it to be stored in the deliberately-not-fully-charged battery.




One of the things you said above I do need to agree with. The computer is also smart enough to know that when you are asking the engine for more power to go to the wheels, it would be helpful (a bit) to reduce the amount of energy being extracted by the alternator. So it can drop the alternator voltage, reducing the currents being generated, and that means less work being done by the engine to turn the alternator. Once you ease off the pedal the computer can bump up the alternator power again.


I don't think it's wise to use the term "free" to describe energy. Thermodynamics is a zero-sum game where everybody loses eventually. Unless you've got some form of external electrical charging, all the energy in a vehicle comes from the fuel. Braking is literally discarding energy. Smart alternators and all the BMS complexity associated with them let you indirectly extract a tiny bit of that excess kinetic energy and use it for your electrical needs instead.

My Dr says I only have approx 58 years to live, and I'm am very poor at reading due to limited education and abilities, so I only glanced.....


However... From the little I was able to glean from the above comments... I'm not entirely sure you are disagreeing with each other.

Maybe just some terminology discrepancy and possible linguistic drift.

Cheers
James

TB a nice rant but as I have already explained, your theory is quickly discarded with the use of nothing more than a digital multi meter.

You have no idea what you are talking about and if you actually took the time, you find there is documented info on the net, putout by vehicle manufacturers, that gives the CORRECT operation of Kinetic Charging.

13 years ago, Honda put out a paper on how their Kinetic Charging system works, and again, it has nothing to do with braking. It is completely controlled by the motor’s load state.

Once again, get a digital multi meter and give yourself an education.

He said engine braking - eg the term of stopping fuel from the engine when the accelerator pedal is not depressed, generally when the engine rpm is higher than 1500rpm.

He clarified he was not discussing the brake pedal.

And he is correct that when you remove your foot from the accelerator pedal the voltage does increase and the alternator load increases consequently further improving the engine braking effect. The effect is insignificant in actually slowing the engine.

I agree this is nothing like the regenerative braking provided by an electric vehicle such as a Tesla which makes a significant contribution to braking and recharge.

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Originally Posted by shack

My Dr says I only have approx 58 years to live, and I'm am very poor at reading due to limited education and abilities, so I only glanced.....


However... From the little I was able to glean from the above comments... I'm not entirely sure you are disagreeing with each other.

Maybe just some terminology discrepancy and possible linguistic drift.

Cheers
James

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Dr Google (or rather a few life expectancy calculators) say I have as little as 30 years to live, so I just skimmed but I agree, both are saying something similar and some of it quite theoretical which might take a computer to prove.

No, he is simply changing his story as he goes along.

JOB DONE.

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Originally Posted by drivesafe

No, he is simply changing his story as he goes along.

JOB DONE.

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Man, you really need to chill out. His story has had some clarification along the way. You’re just seriously aggressive. I have your product and I like it, but I tell you what, there are others now out there that do exactly the same and with programmable set points and I’d just chill out. I just don’t think you’re doing yourself any favours with your aggressive position. You do you I guess but it’s not how I’d run my brand

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Originally Posted by DiscoJeffster

Man, you really need to chill out. His story has had some clarification along the way. You’re just seriously aggressive. I have your product and I like it, but I tell you what, there are others now out there that do exactly the same and with programmable set points and I’d just chill out. I just don’t think you’re doing yourself any favours with your aggressive position. You do you I guess but it’s not how I’d run my brand

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Sorry disco, but read his very first post, where he was concerned he could overload and burn out his alternator.

Now, some posts later, he is an authority on how alternators work.

If he had had any real knowledge about alternators in the first place, he would have known that you can not overload an alternator.

This is alternator basics 101.

As stated above, he is simply changing his story ( as he goes off and reads up on a subject he knew nothing about ).

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Originally Posted by DiscoJeffster

Man, you really need to chill out. His story has had some clarification along the way. You’re just seriously aggressive. I have your product and I like it, but I tell you what, there are others now out there that do exactly the same and with programmable set points and I’d just chill out. I just don’t think you’re doing yourself any favours with your aggressive position. You do you I guess but it’s not how I’d run my brand

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If you read this thread from the start you will easilly see that Drivesafe was curtious, helpful and informative from the start of this discussion.
It took several ill informed and argumentative posts for him to finally loose his patience with the OP.

A far as I can see Drivesafe has the patience of a Saint[thumbsupbig]