# Please tell me if this idea is stupid

edited May 2013 in General
As someone who is in the automotive industry and has a good understanding of how charging systems on combustion engines work, why can the tesla not have its own internal charging system. It says on the site that for every hour the car charges, it can drive 62 miles, so I'm proposing that the car be designed with an alternator type charging system and TWO batteries each capable of going say 75 miles on a full charge. While the car is on the road it only needs to use one battery for the first 75 miles, and when that first battery depletes, the car can automatically switch the the second battery while the alternator starts charging the first. The car could then run endlessly with no need to stop and plug in... Unless I'm a moron who has no clue as to how the batteries and charging system in these cars work. Please tell me why this doesnt work.

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More perpetual motion. The energy to the charging battery comes from the powering battery, minus losses and energy used for motion. It is a very inefficient way to use 150 miles worth of energy.
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But a standard alternator is belt driven, and only makes power when a belt is turning its pulley. It doest draw power from the battery to give it back to the battery, it creates power by being driven by a belt, nothing else. Therefore if Tesla could create a gear driven alternator, any time the car is in motion the alternator could create power and charge any battery, thats why the battery in your car doesnt die from your house to the store.
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There is a system in Tesla car that does just that, it is called regenerative braking. Guess why that is called braking.
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There is no alternator in an electric car, nor is there any belt driven system in an electric car. The drive motor only acts as a motor when under power, when not powered by the battery, the motor becomes a generator that recaptures SOME kinetic energy from the turning wheels until the car comes to a complete stop. When the car is stopped, the motor is a large paperweight that neither generates nor consumes any power.

An alternator works in an ICE car because the engine is ALWAYS running, thus it is able to generate power for its electronics instead of drawing that power from its 12 volt battery.
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I am by no means any kind of expert on electricity transmission, but it occurs to me that if a belt was attached to the axle and then attached to an alternator to create electricity and send it to charge a battery the power needed to overcome the resistance of the alternator would negate the benefit of charging another battery.
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I think you can fly, or at least levitate, if you pull up really hard on your shoelaces.
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Right so what I'm proposing is instead of an alternator that's belt driven, make one that is designed like a distributor, with a small gear drive at the end of an output shaft and insert the shaft into the the drivetrain system which runs using a series of gears. The small gear on the output shaft of the alternator would need very little power to turn, and could easily generate the charging power of a 110 outlet.
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If it takes very little power to turn, it generates even less. There are no free Watts.
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No. Alternators need very little energy to turn yet can yield 110 volts at any rpm. Therefor tesla could create an alternator that runs in conjunction with the transmission so that at freeway speeds it can produce plenty if current to charge one of the two batteries. I could make a small electric motor run almost forever by running a car battery to it and have it turn the alternator. The Battery would constantly be getting power from the alternator and therefore continually power the motor. If the Prius can use the motor braking system to generate power why can tesla not create a self contained charging system? I guess my main question is why does it need to be plugged in if an alternator can charge give it the same amount of charging power. Any electrical engineers here please help me understand this.
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No. Alternators need very little energy to turn yet can yield 110 volts at any rpm. Therefor tesla could create an alternator that runs in conjunction with the transmission so that at freeway speeds it can produce plenty if current to charge one of the two batteries. I could make a small electric motor run almost forever by running a car battery to it and have it turn the alternator. The Battery would constantly be getting power from the alternator and therefore continually power the motor. If the Prius can use the motor braking system to generate power why can tesla not create a self contained charging system? I guess my main question is why does it need to be plugged in if an alternator can give it the same amount of charging power. Any electrical engineers here please help me understand this.
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Kueves87: "Prius can use the motor braking system to generate power "

I think the part you are not understanding is this. The braking system generates power until the car stops. Then it doesn't generate power anymore.

Or maybe you do not understand this "why does it need to be plugged in if an alternator can give it the same amount of charging power."
Because the power is being used to move the car. if you use the power to run to an alternator, it is not being used to move the car. You cannot use the energy twice. You can only use it to move the car, or run the alternator.

You cannot use energy twice.
You cannot use energy twice.
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@holiday. But an alternator does not need power from the battery to charge the battery. If the cars motor uses the battery to run, the battery is draining whenever the car is moving. If you can run an alternator using a gear drive from the drivetrain, you're not using energy from the battery to run the alternator itself you're using the gear drive from drivetrain. The drivetrain spins the alternator which then creates the charging power. How is that using energy twice. The drivetrain is already in motion, all it would do is add another small gear in the mix to run the alternator. If you take an alternator and set it on a bench and spin it by hand it creates power. It needs absolutely no other power source to create power.
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Ok thanks
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You asked for it: "This is a stupid idea".
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Lol thanks ill give up now
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james;
took the words out of my fingers.

pbendo;
"... for every time someone suggested motion was free ..."
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@kueves87, you need to read my response. Ask yourself: why is regenerative braking called braking?

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"using a gear drive from the drivetrain, you're not using energy from the battery to run the alternator itself you're using the gear drive from drivetrain"

What is driving the drive train? The electric motor is driving the drive train,using power from the batteries to do so. Therefore, the power has already been used. You cannot use it again to drive the alternator without robbing power from the drive train that is moving the car.

Did you think the drivetrain magically moves itself?
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@kueves87
I'm sorry, but your idea is stupid.
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You idea is basically suggesting that you should use one battery to charge another. That doesn't make any sense when you want to use both batteries in the same application.

The alternator in a car is being powered by the engine. The engine is being powered by gasoline. Powering the alternator uses up gasoline.

It just so happens, that the way internal combustion engines work is that we leave them running even when they are not in use (like when you're stopped at a red light, or coasting). In this case, true, we put some of that energy to use by turning the alternator to charge the battery and power electronics. It's only "free" in the sense that a lot of the output of the internal combustion engine goes to waste during those times, and so using some of the otherwise wasted energy is "free". However, when you're actually using the engine, like when you're driving on the freeway, for sure, powering the alternator is using up some of your gas. However, the car and all of its functions can't work without the alternator.
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Is... Is this a joke? please tell me this is a joke...
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nw;
periodically, one of these free riders shows up. Search the forum for "perpetual" and you'll see.
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Here is another way to think of it.
Using a belt or gear, either one takes energy to make it move. This will result in slowing the car, which will require energy from the batteries to speed up again.
There are energy losses at every step (gear turning, charging a battery, etc). So the energy gained is less than the increased energy required.

The 110 volt charging would give you a range increase of about 3 miles per hour of charging. Due to the increased energy required by the car, you would loose 4 miles per hour (for example).

What you are suggesting is a more complicated method of what the regenerative braking already does.
The reason they use regenerative braking is it is only used when you want to slow down. The energy when you brake is normally wasted as heat and friction. Regenerative braking allows the car to recapture some of that energy.

Hope that helps.
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Here's an experiment for people to try if they think this would work.
Find a valley. Start at the top of the valley on one side. Run down into the valley, and up the other side. When you get to the top of the other side of the valley, ask yourself if you feel tired. If this idea was valid, you wouldn't feel tired since you gained energy running down the one side of the valley, which you then expended going up the other side.