Citicar - from 48v to 64v

[TomEV]

I recently upgraded the voltage in the Citicar from 48v (stock) to 64 volts. It is interesting the difference a few volts make!

Acceleration has improved greatly. It used to accelerate OK up to about 25, but run out of steam at about 25 MPH, accelerating rather slowly to the max speed of around 34 MPH.

The Citicar now accelerates well (better than many IC vehicles) to just over 35 MPH, with a top speed (unweakened) of around 42 MPH. A big goal was to get the Citicar to accelerate to, and maintain some speed above 40 MPH. At 64v, mission accomplished - thus the change for the Avatar title!

It goes a bit faster still with field weakening. It will do at least 45, but I limit the Citicar to 45MPH in order to not overspeed the motor. At 45, it is doing about 5,000 RPM.

Makes me wonder why I didn't go to a higher voltage a few years ago!

[Ryland]

are you using 8 8v batteries then?

[TomEV]

I am using eight 8v batteries for 64v. I replaced the well-expired set of eight 6v batteries that came with the Citicar about 4.5 years ago with six 8v batteries. It was still at 48v, but about 140 pounds lighter. I used the space under the driver's seat for the controller, aux battery and DC/DC (upgraded at the same time as the new pack).

I recently obtained two used 8v batteries of about the same age and condition as my 'aging' set, and installed them along with the other six batteries for a total of 64v.

Since the original Citicar came with eight batteries, and I wanted to try out a higher voltage, I moved the controller back to where it was originally behind the passenger seat. There is still room for the DC/DC and aux battery under the seat, even with eight batteries. In your Commutacar, you don't have the same space issues.

I don't remember if you have a contactor car, or are using an electronic controller. I suppose that one could replace the 6v batteries in a contactor car with 8v, but you'd have to go with relatively small battery cables (#6 or so) to limit amperage through the stock parts so they don't fail. At speed, amperage really isn't an issue with a C-Car because the tiny motor can only consume full power below about 1,000 RPM; it's the voltage that makes it go faster.

[Ryland]

I switched to an Alltrax 4865 (48v 650 peek amps) after having a contactor fail, arc and vaporize one of the silver contacts and the copper bar it was on, so without changing to another speed controller I would have a hard time bumping it up to 64v.
Also the Commuti-car seat is not as tall as the Citi-car, so if I wanted to go with more batteries I would have to find some that were at least an inch shorter, or modify the seat or floor.
But I'll pass this info on to others, the Citi-car that I used to be the owner of is sitting waiting till spring to be picked up and there is another Citi-car down the road from my parents.
Slightly off topic, but do you know off hand what the max voltage for the Red Top motor brushes are? I thought that you said the original design allowed for 160v but that there were some changes that were made so they would fit in the stock brush holder and I'm hoping to fit one of the sets I bought from you in to the motor for my motorcycle.

[TomEV]

Originally Posted by Ryland

Slightly off topic, but do you know off hand what the max voltage for the Red Top motor brushes are? I thought that you said the original design allowed for 160v but that there were some changes that were made so they would fit in the stock brush holder and I'm hoping to fit one of the sets I bought from you in to the motor for my motorcycle.

Although the Red Top brush material I ordered for the GE 3.5 and 6HP motors will handle 160v, due to the small diameter of the commutator and relatively narrow comm bars, these motors will probably flash over above 96 volts or so. I wouldn't recommend running one of these small GE motors at more than 96v. 72v is better for longevity. At 64v, I hear a bit of complaining from the motor @ 550 amps and slow speeds.

[puddleglum]

Hey, I don't want to hijack this thread, but can you guys tell me what size motors the city cars have an the approximate weight of the vehicle. I don't have one. Actually I've never seen one. Why I'm asking, I have a 6.7"x13.5" 36v motor from a crown reach truck. It sounds about the same power as what you have been discussing. If I ran it up to 60-72v, do you think I could get acceptable performance up to 45mph in a 1600-1800lb car? Would it likely be similar to your citicars?

[TomEV]

Originally Posted by puddleglum

Hey, I don't want to hijack this thread, but can you guys tell me what size motors the city cars have an the approximate weight of the vehicle.

The motor on my Citicar is a mid-1970's GE series motor rated at 3.5 HP (36v, 98 amps). It is about 6.8" in diameter and 11" in length. It weighs about 57 pounds.

The Citicar itself weighs in at about 1,300 pounds. You'd have to add 150 to 200 lbs for the driver, depending on how much they weighed. If I have a passenger in the Citicar, the top speed is about the same (45 mph) but the acceleration is somewhat slower.

The Crown motor will likely have a bit better performance than my GE because of two factors: you have more than one gear, and the motor itself should have more torque (longer armature). It should get a 1,800 lb car to about 45 MPH at 72v, but it will not get you there very quickly. I imagine you will have about the same performance at 72v as did Ben Nelson with his 72v Metro.

[puddleglum]

Thanks for the reply and for letting me jump in on your thread. It's all still theory and investigation for me so far, but maybe one day it will become reality. I remember reading about the Citicar or one of it's variants back in the 70's when it came out and thinking they were pretty cool. I might even have the magazine around somewhere.

[MetroMPG]

Congrats on the successful upgrade, Tom!

Still no plans here to bump the ForkenSwift past 48 volts. I will admit the thought crosses my mind now and then, but to be honest, 48 volts is "good enough" for where & how the car gets used.

[TomEV]

For some reason I'd thought you went to 72v... But I'm sure ForkenSwift is somewhat faster than the Citicar, even at 48v!