Topic: some questions and answers on EVs

[piersdad]

1, If everything stays the same e.g.. batteries, controller, weight of car, voltage etc, and all I do is change the motor to a bigger H.P., will it increase or decrease the range?

The bigger motor will, especially during acceleration, will be more efficient,  as a smaller motor can be over loaded and inefficient.
The  neev had small motors but we upped the speed and voltage to compensate.
I.e. a smaller dc series motor at 3 hp 24 volts 1500 rpm is identical to a 48 volt motor 6 hp 3000 rpm

    I presume it would have slightly more torque and acceleration but would it pull less amps at the same constant speed?

Slightly less as it could be in a more efficient range of power

2  If running two motors, can you do away with the differential?   I presume that is a yes as with the NEEV's. Is there any advantage over front or rear wheel drive.

  The twin motor will automatically differential and even act as limited slip diff.
We found that this gave us as much traction on 2 wheel as a 4 w d vehicle
The conzept easily climbed a shingle drive that was a down only for conventual cars.

 And one controller for both motors  we did have series parallel switching on the motors  to get full efficiency at half speed on the conzept

3   If front drive would it give a lot of torque steer under acceleration? Is it best to run the motors in series or parallel? One controller or two?

Series or parallel makes no difference on FWD  for torque steering as  in series the current is shared and parallel  the motors share the current according to the road speed they are at.
I.e. the outer wheel will take less power than the inner wheel in a turn and actually try to steer the vehicle straight

    As for reduction ratios, do you start with the top speed required and max safe motor speed to get the ratio? Or is it a bit of trial and error?

Gear ratio  is  for top speed and max motor speed  how ever a rule of thumb is to not exceed 7 volts per commutator segment  ( ie a 3 segment toy motor will be a bit too much on 20 volts)
So a 60 segment motor commutator could be used on 400 volts but would have to get fed a bit at a time as it would screw its shafts off under full voltage all at once.
at excessive speeds windage losses and comutator losses tend to rise

   Would a belt drive be quieter than a chain drive? Does having one ratio limit the top speed to much to get the car from a standstill to accelerate away?

Belt drive is quiet but chain  well set up is also quiet
Rule of thumb for belt from memory is to find out the max pull at the diameter of the smallest pulley and calculate the exact pull on the belt and 25 mm belt with at least 3 teeth engaged will take 30 lbs pull refer to manufacturers data for HP transmitted bvy various sizes of belt and you will see there is a corelation between belt width/number of teeth engaged/and power transmitted.

   Not sure which way around it is, but if you started them in series and then electrically shifted to parallel at a certain speed ( or the other way around)

   Would that give you the low down torque and then the higher speed for cruising?

Series for start equals half volts and speed but full torque  for each motor
 parallel is full voltage /speed for both motors
 

 
Question 1 is something I would like to try on the VW to try and increase the range. Would welcome your thoughts before I tear it all apart and end up making it worse.

Find out the current speed graphs for the present motor if you can and if the cruising current is in  an overload situation then ether raise the gear ratio and voltage of get bigger motor.
 Over a certain current for a particular motor excessive heating takes place instead of power output.

I thought a bigger motor might have more torque and pull less amps on the open road.
Question 2 is I have been thinking about converting a car but trying to reduce as much weight as possible by getting rid of  the diff and gearbox.

When going to twin motors each motor has its own losses and often this pair of losses can exceed the losses of a diff and its weight
The neev suffered with this but we found out too late  and beware of a worn diff as Bill Leaman had an unexplained rise of 60 amps due to a worn diff in his vanguard

And also trying to reduce some of the transmission losses going through a diff and gearbox.

 
 Gear box in top gear is direct except VW and mini Morris and many fwd cars
A worn FWD gearbox, or intermediate gear  as on the morris mini,can cut MPG from 60 mpg to 40 mpg and have the owner scratching their heads.

glad to answer questions here as it gives me a chance to give the down to earth info that allows some one to find out where to start their research.
nothing like finding out where to start asking questions