Why can't electric car batteries be recharged by engine driven generators?

Question

Why can't electric car batteries be recharged by engine driven generators?

Answer 1

They do.  Gas/electric hybrids use generators in the wheels to recharge batteries.  However, since no machine is 100% eefficient (2nd law), they can never be fully charged.  That is why full electric vehicles don't use them.  But they are good for a supplement to something else.

Answer 2

Because that would be a perpetual motion machine.  A motor that runs on electricity cannot generate more energy through a generator than went into it in the first place.  And any energy used (i.e. friction, heat, moving a car) is consumed.

Otherwise you'd have a car that ran forever on only it's initial battery charge.  This is not allowed according the basic laws of thermodynamics.

Answer 3

the principle of your question is simple. if you have an engine driven generator, and all it does is recharge the batteries, you have whats called Series Hybrid. a good example is the diesel electric submarine. the diesel gen sets provide power for recharging while on the surface as well as power for the propulsion system. the current production hybrids are called Parallel Hybrid, meaning the engine does not only recharge the battery pack but also powers the drive wheels thru a transmission. in a Series hybrid, the engine can be tuned for maximum efficiency because it will operate at a constant rpm. Parallel Hybrids will never be as fuel efficient as Series Hybrids. but then on the other hand, oil industry really doesn't want fuel efficient vehicles now do they????? here is another example of a series hybrid

Answer 4

U can but every time u change from mechanical energy to electrical it will cost u about 40%. So what advantage were u looking for??

Answer 5

hybreds you dont plug them in..they are charged by brakeing motion and gas motor

Answer 6

A totally electric car can be made and it can run on nothing but Kinetic energy recourses save start. Kinetic energy is utilising every single operation that can create  electricity using any movement of vehicular motion be it brakes bearings any component that recourse's friction creates kinetic energy if the scientists used their head just a little bit we would already be driving self powered cars but if they gave us it all at once there wouldn't be any more to give .IE No more markets to exploit. They should start looking for markets in other areas. instead of raping our planet.

Answer 7

Because that would violate the second law of thermodynamics.  Eventually, the battery would run down because you can never get as much power from the engine as you put into it.

Answer 8

If I'm not mistaken, gas/electric hybirds operate like this.  A purely electric system wouldn't be able to work like this.

The problem is that no system is 100% efficient.  A battery turns a shaft, that is connected to a transmission.  Some of the energy from the motion of the crackshaft is lost as heat, also, friction robs the engine of efficiency.  

If an engine is as efficient as possible, you still lose some amount of the potential energy from all this.  For instance, a battery has 1000 units of power, and a car needs 1 unit of power to travel a mile.  The car isn't going to travel 1000 miles because a portion of the unit of power is lost to things like friction and heat, rendering the engine less than 100% efficient.

Adding a recharcher would only exacerbate things.  A greater portion of each unit of power would be lost in order to recharge the battery, also, no charging mechanism can return 100% of the power given.  So you lost some power to run the charger, and the charger loses some energy when recharging the battery, so the overall loss of energy goes up.

It would be theorhetically possible to create some kind of system that is connected to a charger, but not connected to the engine.  Kinda like having a wind turbine charge the engine while the car is in motion, of course, you have to make sure that the turbine can provide more energy that is lost from the engine having to carry its weight.

Adding something like an alternator would actually rob the car of power that could be used to drive it.