Ben Nelson's Electro-Metro Build thread

[bennelson]

Well, here is one more "-ectomy". The plate that covers the front of the car where the radiator wasn't. The radiator on a Metro is so small, it only covers half of the front area, so they cover the other half with this sheet metal.



I also played around a bit with my old Yellow Top mock-up (not that I am going to use those, but it was handy) to see what there is for space for batteries.



Looks like there's lots of room in there for batteries.

And that's only under the hood. I still have all that room in back!

[Daox]

What is your planned battery configuration? I know you said 72 volt setup, but are you using 6Vs or 12Vs?

[bennelson]

I still haven't decided yet.

If I do 12 volts, I will rig them up in "buddy pairs" so I still have a decent total amount of amp hours.

12 volt would also be more flexible in positioning and arranging inside the vehicle. 12 volts would be almost the exact same size as the Yellow Top mock up I have in there.

6 volt golf cart batteries are supposed to be better in terms of deep cycling and length of life. They are more specialized, so they have to be bought at a dealer, instead of just off-the-shelf.

I think I will have to make up a mock-up for a Trojan T-105 and see how it looks and fits in the car. Not having a radiator makes some great space for two big batteries right up front!

From what I hear, every EVer ruins his first set of batteries really fast. With that in mind, I should get the cheapest batteries I can, maybe even used ones.

I can tell you one thing. My first ride in the Geo will be with four 12 volts on the passenger seat floor!

[bennelson]

Getting excited about this project.

I am going to order brushes for the motor later today.

I would like to get a controller and throttle control soon as well.

Once I have those items, I can put in the motor, and start spinning the wheels on the Metro. Then I can really begin to experiment with it!

Right now, I am planning on using a Curtis 72V controller. Not sure what to use for a potentiometer.

Looks like a PB-6 is about $73 (has microswitch) and a PB-5 is $66. Those prices don't sound bad for having a solid piece of equipment designed specifically for what it does.

Pot Boxes

Darin, what are you using in the Forkenswift?

[Daox]

If you are going to go with 12 12v cells, why not go up to 144V? You'll still have the amp hours avaliable, but twice the voltage. I understand the controller would cost more (unsure of actual price), but maybe its worth it?

[MazdaMatt]

Is it a practical idea to use a parallel/series switch like a 2-speed transmission? Start out in 72V for low speeds so you have the parallel current handling ability, then go to 144 in top gear when you need the higher speeds?

[MetroMPG]

Series/parallel is a decent option for speed control, but typically at lower voltages. The transition between 0-72-144 would be enough to break things. The Citi/Comutacars had 3 speeds using a contactor controller: 24v(across a resistor) - straight 24v - 48v.

Ben: the ForkenSwift is using the potbox from the forklift. It's got high & low microswitches (we're only using the low), return spring, etc. I had to change the potentiometer itself though, since the one from the forklift had different resistance than what we needed (using a $2 one from Radio Shack).

[bennelson]

Originally Posted by Daox

If you are going to go with 12 12v cells, why not go up to 144V? You'll still have the amp hours avaliable, but twice the voltage. I understand the controller would cost more (unsure of actual price), but maybe its worth it?

Yeah, mostly the big consideration is cost. A Curtis 144V controller is $1400. A slightly used NEV 72V controller is 300.

Also, the motor I am using is originally designed for 36 volts. I will be running higher quality brushes in there, and eventually advancing the timing as well. I really have no idea how the motor would handle 144V.

I actually have considered the idea of using a PWM controller in combination with contactors to make a very controllable vehicle at lower speeds, and then having it kick over to a "direct connection" for a higher voltage "overdrive".

I wouldn't be able to use the controller when the pack is configured in the higher voltage configuration. It would just be a "cruising gear". Could be activated with a momentary on dead-man's switch - as soon as you let go of a button on the steering wheel, or trigger on the stick shift, it would drop down to the lower voltage, controller-run mode, which would give you full speed control over the motor again.

Another reason why I am thinking 72 volts is that I already have a high-amp 36 volt charger. I could rig up the pack to be split in half for charging (2 36V legs). For 144V I would need a big fancy 144v charger or a dozen 12 volts. That is just one more thing to add to the cost of the project.

[bennelson]

Originally Posted by MetroMPG

Ben: the ForkenSwift is using the potbox from the forklift.

Uh oh, I have a joystick control from the forklift I took apart. I might just have to put a multimeter on there to figure out which wires go where.

Just imagine my joystick controller mounted to the Metro dashboard!

[bennelson]

Hmm - I checked the forklift joystick and it's not going to work, it uses a funky connector which the other half most have been sold as scrap with the rest of the forklift.


My Metro came with both driver and passenger side mirrors - unfortunately, neither was attached. Both had been snapped off at some point in the past.

I figured the best way to reattach the mirrors would be with longer screws running through the broken off stubby bits left on the old shorter screws.



The driver side mirror went back on. Too bad there is a little broken on the front of it as well. Two of the drywall screws went in great. The third one sounded a little weird. Looks like it skipped out of the old hole.

Think anyone will notice?

I am not sure if I will reattach the passenger mirror, or just make a "mirror-delete" black plastic cover to go in place of it.

I wiped down the door interiors with some Armor All. It really suprises me still how good condition the car interior is in.



I threw one of my old electric bicycle batteries into the Metro to test out the radio, lights, etc. Holy Cow! This thing has Daytime Running Lights on it! Hmm. Might not be the best thing in an electric car. I would like to drop any electric loads I can. I did also notice the actual headlights dont work. (the DRLs do, but full headlight mode doesn't) Maybe it's a fusible link or something.

I also ground down a little rust around the engine compartment and painted it with some gloss black oil-based Rustoleum.

Since there is no engine or transmission in the car - the easiest way to work on it is to actually get inside the car. From there, I was able to get a good look at the control arm support on the drivers side.



The passenger side looks pretty good, but I think I will need to do something on this side. Not sure what yet. Guess I will try to scrape and grind what I can do here, then weld something on and oil it all up?

By the way. If you are inside a Geo Metro engine compartment, and think it would be funny to see if you fit inside it with the hood closed - don't do it. You will have to call your wife on the cell phone to have her pull the hood release. (don't ask...)


I also checked and labeled a couple of the misc. cables and things under the hood. Looking at the dashboard, I was wondering about reusing the fuel gauge as a voltmeter/state-of-charge display.

Figured all I had to do is find the wires that originally went to the gas tank and check what kind of signal came from there. I looked under the car where I removed my gas tank. Imagine my surprise when I couldn't find any gas tank wires! Where are they on this car?