[koolkev]

Could a Leaf motor/transaxle move a 4900lb car to 75mph in a reasonable time?

If I wouldn't mind short range, like 45 miles, what is the smallest battery pack to drive a leaf motor?
Assume 3 miles per kw so 15kw
Tesla's are nominally 24v, no? What is the minimum voltage to run the leaf motor?

 

[remy_martian]

Speed depends on the car. Speed depends on motor voltage.

45kWh, not kW.

0-60 in maybe 8 or 9 sec with that weight as a wet thumb in the air guess.

EDIT: In your case, 15kWh pack size. The problem at thos point is getting enough current out of a pack that small since you'll need several hundred volts to run the Leaf motor. Which then punts the Leaf and gets you into a 96V/144V motor. A Tesla module has the wrong granularity for such a small energy need.

 

[brian_]

If I wouldn't mind short range, like 45 miles, what is the smallest battery pack to drive a leaf motor?
Assume 3 miles per kw so 15kw

45kWh, not kW.

As remy_martian said, what gets you 3 miles is 3 kWh (kilowatt-hours) of energy, not 3 kW (kilowatts) of power, so for 45 miles you need 45 kWh. If you understand the difference between power and energy, then use the correct units to communicate effectively; if you don't, then it's time to do some reading.

 

[brian_]

Tesla's are nominally 24v, no?

Not quite. The modules of the Model S and Model X batteries (before the Plaid version) have six groups of cells in series (6S), so their nominal voltage is about 22 volts... and 16 of them in series run at about the voltage expected by the Nissan Leaf components. Model 3 and Model S Plaid modules are very different.

 

[kennybobby]

Some back of the envelope calculatus,

For a 4900 lb vehicle to travel at 75 mph requires about 25kW depending upon tire rolling resistance, frontal area and Cd. What are you building--some kind of truck?

So the size of the pack needed to accelerate up to that speed depends upon how quickly you wish to get up to that speed--10, 15, 20, 25 seconds?

The windings in the leaf motor are wound with a relatively small gauge wire to allow for operation at the high voltage (400VDC) of the pack. At 75mph in a leaf the motor will be spinning at around 8400 rpm. i don't know the motor constant but suspect that the back emf generated in the windings at this speed will be quite high and a substantial fraction of the pack voltage. Somebody may have measured it and posted on this forum.

What kind of driving will you do to require 75 mph and only drive for 45 miles--a daily commute on the interstate?

At 50mph the steady state power is much less at around 10kW.

 

[koolkev]

traveling short distances on the highway. Like 5-10 miles to local spots.
I was hoping to get to 60-70 in less than 10 seconds. so that getting on the highway wasn't a problem. But traffic around here even on the surface street moves 40-50mph.

 

[Electric Land Cruiser]

Check out my build thread I am powering a 5000lbs Land Cruiser with a LEAF motor. Performance is good. Only have done 45mph maximum so far but it had no problems getting to that speed. Can easily accelerate with normal traffic.

I have geared mine down a bit from a standard LEAF however. From about 9:1 total reduction to 11:1.

The Electric Land Cruiser EVJ80 - Nissan LEAF + Resolve-EV

Nice work. I follow you build closely, as I’m a few months behind you in my build. What size is your box? Thanks! The box is 36x20x16 inches externally.

www.diyelectriccar.com

 

[brian_]

At 75mph in a leaf the motor will be spinning at around 8400 rpm.

... assuming the same gearing and tire size as the Leaf. The gearing is the same since the transaxle is being used, but if the tires are a significantly different height then the motor speed for a given road speed will be different.

i don't know the motor constant but suspect that the back emf generated in the windings at this speed will be quite high and a substantial fraction of the pack voltage.

At 8400 RPM the stock Leaf configuration is still well within the speed range (about 2700 to 9800 RPM) in which power is limited by the controller (to 80 kW, 110 kW, or 160 kW, depending on battery) to protect the battery, not yet limited by available battery voltage.

 

[brian_]

In your case, 15kWh pack size. The problem at thos point is getting enough current out of a pack that small since you'll need several hundred volts to run the Leaf motor.

The obvious solution is to use the entire pack from a plug-in hybrid, which has about the same overall voltage as a Leaf, but only about 15 kWh energy capacity. These batteries can handle the power demand of a Leaf motor, at least in the 80 kW and likely 110 kW versions, at least for the duration of an acceleration burst. The classic example is a Chevrolet Volt.

A Tesla module has the wrong granularity for such a small energy need.

True, any pack configured to deliver much more than 15 kWh (which means any modern EV pack) will have only a fraction of the desired voltage when you use only a fraction of the pack. If you take modules from a pack which is six times as large (in energy capacity) as you need, you will be using only one-sixth of the modules and thus get only one-sixth of the voltage.