Citicar - from 48v to 64v
 

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!

are you using 8 8v batteries then?

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.

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.

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.

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?

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.

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.

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.

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

Oh, I don't know about that.

Want to do a virtual drag race? :)

Three Dirt Cheap DIY Electric Cars – Part 3

That's flat out, probably a 3rd gear start (I forget whether I had yet learned that it accelerates better in a higher gear), with a 400A controller.

Virtual Race Info:

With my Citicar at 48 volts, it would accelerate like this:
0-25 ~ 6.5 seconds.
0-32 ~ 16.0 seconds

With a top speed of about 37 MPH field weakened. I estimate that the 48v 1/8 mile time/speed would be about 19 seconds @ 36 MPH.

>>>>

At 64v, I rarely use FW as it accelerates just fine without it. It gets to 40 MPH as well as a normally accelerating IC vehicle, and does about 42 or so without FW.

One nemesis was the tunnels leading in and out of Alameda. The speed limit is 45, and at 48v it would get there reasonably well (going downhill...) and was able to hold 45 on the floor of the tunnel with FW on. Going back out (uphill) was another matter. Even with FW on, the speed wold decay to about 30 to 32 MPH. With FW off, it would probably decay to about 27 MPH. Once outside the tunnel on level ground, it would take a while to accelerate back to about 35.

At 64v, the speed downhill and on the floor, without resorting to FW are the same as I limit it to about 45 to keep from over-revving the motor. Going uphill, it now maintains 40 with FW on, and gets back to 45 once out of the tunnel quite easily.

Well, not only is your car more functional now, you won the virtual drag race even before upgrading!

The ForkenSwift suffers from a pretty significant weight disadvantage though: 2070 lbs, empty, vs the Citicar's 1300 lbs.

But at least ForkenSwift doesn't rain inside when it is raining outside! The old-school 'side curtains' keep some of the wind out, but I really don't like to drive the Citicar in rainy weather.

You're right - the rain doesn't come through the windows of the ForkenSwift.

It comes through the Flintstones-style holes in the floorboards in the form of road spray. :)

That is why I really like the Commuti-car doors with their solid windows that slide instead of being removed to open them, they are pretty decent in the rain, humidity still builds up in the car, part of why I got a small dehumidifier that I plug in.
Tom, any idea if my 6hp motor is really any bigger then the 3.5hp motor you have? I have a "low speed" rear end so my top speed is also about 35-37mph at 48v but I feel like I accelerate pretty well.

The GE 3.5 and 6 HP motors are virtually the same electrically - Same field shoes, same brushes, same armature windings. Main difference is the armature shaft is male on the 3.5, and female on the 6. (there are a couple of other structural differences so they mate properly with the Terrell or Dana axle).

They have different ratings because the 3.5 is a 'closed' motor (no ventilation) while the 6HP has a cooling fan.

The high speed is mostly limited by the amount of RPM you can attain before counter EMF forces self-limit the motor RPM. 35 to 37 MPH is what I would expect in a stock Comutacar/Dana axle, and about 32 - 34 in a Citicar/Terrell axle. Ways to decrease counter EMF force is to use field weakening (weakened counter EMF, allowing the motor to turn faster at the top end) and/or increasing the voltage. Going to a higher amperage controller only affects low speed acceleration, as these motors can only use over 400 amps up to about 1,000 RPM.

You'd probably only notice the difference in speed and acceleration if you broke out the stop watch and timed a 48v Citicar and a Comutacar zero to top speed. Do you have any 'virtual drag race' numbers for your Comutacar? With the Comutacars I've driven, (sample of two) I found them to be somewhat slower to accelerate - but very much quieter. My 'silent' EV is anything but! I am very jealous of the Dana axle... Imagine a '30's pickup in granny low - and then put that gearbox sound in a plastic car, going 35 MPH.

Replacing the transaxle was one reason why I got a basket case Comutacar - unfortunately, someone had modified the transaxle with 12:1 ring and pinion - not terribly useful. I donated the Comutacar to the local high school for a project/instructables car as it didn't have any of the body panels, and was missing too many parts to make it into a road worthy vehicle.

I know this doesn't belong here...
 

This doesn't belong here...but could anyone tell me what the dimensions of the flat area of the little roof?

Although I sold the Citicar, if I remember correctly it was about 38" x 38". I was planning to put this solar panel on the roof, and it was just about the right width, but would hand over front/back about 2":
Kaneka 60W 48v Thinfilm Solar Panel

Mine is at my parents waiting to get new brushes (Thanks TomEV!!!) so I can't check on the roof size right now, but I bought enough PV to cover my roof and figured it'd give me 2 miles of extra range per day, but the big advantage would be the constant charge that it would give the batteries, adding years on to their life.

I have a Kaneka 60, I could make a solar panel kamback, I wonder how long it would live? :)

The tough part might be mounting it without breaking the plastic body. You could mount it to the tube frame/roll bar, but then you might have problems with leaks.
The Keneka panel seems to be a good match for the 48v pack. With a good amount of sun, it might recover about two miles in a day.

Commuti-cars have rain gutters above the doors, perfect for a roof rack to bolt to, Citi-cars... they are tougher, I would mount something to the bumper mounting points before I drilled the body.