Building an electric car, have techincal question?

Question

Question #2 (re-hash of question #1):

Still planning on converting a gas car to electric. Can I install two DC motors in-line to eachother (output of one attached to the tail shaft of the other, and then the output of the other attached to the cars transmission), with the express idea of shutting off one motor while cruising on the highway. The motors will be either two 60V DC or a 94V / 36V combination. The shutdown motor will not be acting as a generator or anything. It will simply be free floating.

I know that there is added weight and the second motor will have a minor drag effect, but this is not the issue in question here.

I would like to know if there will be a noticable increase in overall range (15%+) for this type of system? Also is the total power output of two motors totaling 120V DC the same as a single 120V motor (HP and torque, not electrical power)?

For now please avoid the issue of motor synchronization and controller requirement.

Thank you.

Answer 1

I'm thinking of two entirely separate engines.  It would be like mounting two engines in a front wheel drive car.  Leave one engine and transaxle in the front.  Mount the 2nd one over the REAR wheels.

Do you know how train locomotives work?  They have electric motors on the drive wheels.  A diesel engine produces electricity which powers the wheel motors.  

Now THAT's  a hybrid.

There are serious problems with running two engines on the same drive shaft. Usually you will need a viscous coupler (like a torque converter) to allow some slippage without destroying your transmission or engines.

Answer 2

It would be more efficient to run one motor of twice the HP than it would to run two motors coupled like that.  A motor (unlike a gasoline engine) only uses the power that it needs up to its capacity.  A large motor adds weight, but not as much as two smaller motors, so the ultimate answer is no, it will not increase range at all.

I have also investigated this, as I was considering putting 4 pancake motors, one on each wheel, on the car.  I discovered that with current technology, it is more efficient to have one motor to drive a differential to the two back wheels.  The drag created by the diff is less than the loss due to the inefficiency of having 4 motors, unless I was willing to purchase very expensive motors and a super high tech controller for them.