Project: The Electric Booger (budget EV conversion - '92 Mazda MX-3)

[mechman600]

I still have a Mazda 1.6 engine sitting in my garage that nobody wants to buy. It has been on Craigslist since I removed it from the car, but whenever someone contacts me and asks how many miles are on it, they quickly hang up when I say 280K km. I finally decided to scrap it at work, but I don't have a pickup truck. I could easily borrow one, but coordinating help to lift the engine into the back simply hasn't happened yet.

So I took some inspiration from an old Johnny Cash song:

http://www.youtube.com/watch?v=5GhnV-6lqH8

I started stripping the engine down so I could haul it to work in the Electric Booger "one piece at a time". Anyway, just for fun, I took some pictures. For this many miles, it's actually in pretty good shape!

[mechman600]

Plug it in and walk away.

There's only one thing from making it that simple right now: my accessory battery charger. It's a Schumacher smart charger - 12/8/2A. Every single time I plug the car in to charge I have to go inside and push the charge rate selector to turn the Schumacher on to charge the 12V accessory battery. Sure, it only takes about 20 seconds extra, but it's the principle! I want be able to plug in and walk away.

So today I finally found a cheap microprocessor controlled 2A charger:

eBay. $18.99 with free shipping. Seems like it is finally the last piece of the puzzle.

Now how about some more pictures of the ICE teardown....


Amazing how good the bearings/journals looked. They honestly looked like brand new. This is with 281K km (175K miles). Seriously.

The pieces are now small enough to haul in the back of the eBooger to the scrap bin. How ironic....

[MetroMPG]

Plug 'n' play is nice.

What are you going to do with the extra room in the garage??

And what about when the nice weather returns... ride the bike or keep driving eBooger?

[mechman600]

Originally Posted by MetroMPG

What are you going to do with the extra room in the garage??

Probably just just enjoy the extra space for now!

And what about when the nice weather returns... ride the bike or keep driving eBooger?

Both. I will license the bike when it gets warmer out...April, maybe. I will probably commute with the Electric Booger most of the time and ride the bike a couple of days a week.

I have found that while I love commuting on a motorcycle, I tend to not go for "fun" rides when the bike is my commuter. The bike becomes an appliance, which I don't want. I think keeping the eBooger insured will prevent that from happening.

[puddleglum]

Hey mechman,
I have a couple of questions about your motor. I think I might have a line on a pair of these same motors. Were there any other numbers on the data plate on your motor other than the MVX-4003? Is yours rated for 72 volts, or is it 36 volts and you are running it at 72v? In one of your later posts, you say the size is 6.5"x18" but in an early post you said it was 7.5" dia. Is the later one the actual dimensions? Is the 18" overall or case length? The ones I looked at appeared to be 6.5" dia. and quite long but I didn't have a chance to measure them. If these are the same motor, your conversion gives me a pretty good idea of how it would perform. Would you use that motor again if you could use it with a proper sepex controller?

[mechman600]

I don't remember what the datatag says on it. I have a feeling that it does't mention a voltage or I would have remembered the voltage rating. Unfortunately I cannot see the tag because of the batteries on top of it. I may be able to see it from underneath, but that will have to wait for another day.

I think it could handle more than 72V. When I was running lower field current than I am now, even at 20A field and full 72V to the armature at high revs the brushes were not arcing, at least that I could hear. The higher you go with field current the less chance of arcing there will be.

I just went out and measured the motor case: 7-3/8"X18". The case is quite long because it houses the brushes/commutator at the drive end, where most motor cases end before the brushes on the non-drive end.

For a 72V conversion I would advise you to stay away from this motor. It is simply too small and in my ~3200 lb car it gets quite warm after a 20 minute drive. (That being said, my brushes and commutar look perfectly fine after 1000 miles). If you plan to run higher voltage it may not be too bad (less amps and less heat), but good luck finding a sepex controller higher than 72V anyway. I suppose you could always buy a higher voltage series wound/PM controller to power the armature and a separate small controller for the field like I am doing.

Also, running a higher voltage with this motor will require you to run it at very high speeds (5000 rpm+) unless you really crank the field current up, and I do not know how much current the field is actually capable of handling. I give my field 50A peak which makes the power peak at 3800 rpm. That's when my controller is in full bypass (I can feel the bypass kick in just below 50 km/h (31 mph) in second gear), when the motor is getting the full 72V. With the same field current (50A), this would not happen with a 120V pack until 6300 rpm, and I do not know if the field can handle much more than 50A to lower this rpm.

If you are thinking of going 72V, I suggest you get a larger motor. It's backwards thinking to my logic when I was motor shopping, but 72V will generally require more amps to achieve acceptable acceleration. And this heats up small motors quickly.

[puddleglum]

thanks for the reply. I'm still so far away from actually building a car it's still just a dream. Life just keeps getting in the way, but I'm thinking I may still try to get these motors anyway, if I can, since you have proven they can work. If I can get something better before I'm ready to start building something I might. My thought was to run the two together in tandem at 72 volts. Either that or find a really light car. It would complicate the build but give me twice the power. I should be able to run both motors off of one controller, I think. Kelly actually makes sepex controllers up to 144v, but I don't think those motors would take it. I know they don't have the best rep. but some guys are happy with them. So your field peaks at 50amps, what voltage are you running the field at? What gear are you in at top speed and what is your motor rpm? Hope you don't mind all the questions, but you are the guy that made it work.

[mechman600]

Originally Posted by puddleglum

Hope you don't mind all the questions, but you are the guy that made it work.

Hey it's no problem at all. This thread is meant to pass on things I have learned the (hard way!) to others.

It would be awesome if you could pull off coupling both motors together. You could then series-parallel switch them and broaden your power band like crazy - with an electric "shift".

I almost bought a Kelly "sepex" controller. The " " is because it really isn't a real sepex controller. Notice that on their ordering screen you specify what field voltage you want. The controller gives the field this voltage whenever the throttle is depressed and does not vary it like a proper sepex controller. I ran my motor with a constant field voltage for the first while and believe me, it wasn't much fun. It makes for very weird throttle response - like a farm tractor where 25% throttle = 25% rpm, 50% throttle = 50% rpm, etc.

My field controller is a Kelly controller and it has proven to be very reliable so far.

The MVX-4300 has a 1 ohm field, so 50A requires 50V.

I haven't reached top speed yet. I just never bothered once the weather got cold and the batteries became "lazy". However, once it gets warm bennelson, MetroMPG and I are apparently having a "virtual drag race", whatever that means!

The fastest I have reached is 85 km/h (53 mph) in 3rd, which is 4470 rpm. It won't go as fast in 3rd now that I am giving it more field than back then, but 4th will be much stronger now, plus I have AGM batteries now, so it should do 90-95 km/h (56-59 mph) now. But I wouldn't do that for long and possibly bake my tiny motor.

One of these days I will do a proper top speed run.....

[MetroMPG]

Yes, I am preparing to lose badly our virtual drag race.

Reminds me: I'd better plug in the old girl. It's been sitting since November, and I'm sure the pack would like a sip.

[mechman600]

I have been using my new accessory battery charger for a couple of weeks and I am proud to say that I can finally plug the car in and walk away.

My old accessory battery charger was a Schumacher SC-1200A. 12A/8A/2A. I had to turn it on manually every time I plugged in the car. Annoying. And it wouldn't quite keep up with the traction pack chargers, meaning that if I did too many short charges or didn't do a long float charge once in a while, my accessory battery would fall slowly behind after a few days.

If you are going to charge an accessory battery with its own charger instead of using a DC-DC convertor (like most sane people do!), the trick is to give it a charger that charges slightly quicker than the traction pack chargers.

So I tested the Schumacher. It turns out that the "2A" mode really outputs 1.3A. EEP. What a piece of junk. I tested my new $18.99 2A ATV/motorcycle maintainer (immediately after testing the Schumacher) and it outputs 2.3A. Much much better. This 2A maintainer does not require switching anything on, which is the real bonus and the main reason i bought this charger. Plus, once the battery is fully charged (14.4V) it switches to a float of 13.5V. Not even the Schumacher did that.

Needless to say my accessory battery has been much happier lately. I can tell by the tone of my vacuum pump and the normal speed of my windshield wipers.