Ben Nelson's Electro-Metro Build thread

[Nerys]

If it was that easy to build a long range EV for $3000 there would be a lot more long range EV's here now wouldn't there :-)

plus its not like I am driving around joy riding where if a battery pukes I walk home and get my jeep and toe dolly.

If this happens coming home from work I could be 30 miles from either location at 0300 in the morning in the middle of no where on 206.

[Christ]

I never said it was easy, I said it would be reasonable to think that a resourceful enough person could do it. Someone who's willing to build the project over a few years, stock pile parts, etc. could do it.

If it's not for you, it's not for you. Nobody but you is going to change your mind, and you'd probably have to own one for a while for your mind to change... sort of a Catch 22, is it not?

[jyanof]

Originally Posted by bennelson

Hey Guys,

I did go up a hill today that seemed like the Open Source controller didn't perform as well as the Curtis did.

I can't say for sure though, because my charge may have been a little low. I have been messing around with the float voltage on the charger a bit lately, so it might be that.

I was wondering how this would work on lower voltage controllers. If Paul left the code the same, I suspect that's the source of the problem (as he alluded to).

The way that worked well for my 144V setup was this: At zero PWM, full torque is reached at half throttle. If PWM is maxed out, only half the torque is ouputted. It sounds weird, but at 144v, I'm never using more that 60-70% PWM, so I pretty much have all the torque that I require. At lower voltage, you're probably operating at higher PWM duty cycle, so the code will behave differently.

Paul, there's this line in the code:

throttlescalar = 1085-3*OCRavg/2;

If you make that line:

throttlescalar = 1085-OCRavg;

it'll make it so that at full PWM, you still have full torque available. (the 1085 represents 2x512, plus a little buffer. So, if you subtract 512 (max PWM), and divide by 512 in one of the next lines (not shown), you'd have a scalar of 1, and thus full current. Right now, it's a scalar of 0.5, and thus less torque is available at higher speeds).

Might be worth a try - not sure how it'd affect the 'feel', but i bet it'll be fine.

[MPaulHolmes]

That makes sense. Maybe I should mail him another microcontroller. Man, I need to get a bootloader on it.

Joe, are you still seeing 480 amps (or whatever) with the software right now?

[jyanof]

Originally Posted by Nerys

is there simply no practical way to move 3500 pounds 65miles on a charge? I so badly want to go electric but my one way commute to work is 54 miles and would need at least 10 miles "buffer" to be safe.

In the heat of AZ and our modest hills, I can accomplish this in my EV. It's a 89 Corolla with 24 6V floodies - it's really heavy and accelerates slow, but appears all stock. There's 7 under the hood and 17 in the trunk. 1500 lbs of batteries for a total weight ot 3700 lb, so that's about 40% of the total weight.

My commute for part of the year (track season) is 52 mi round trip and my longest drive so far has been 55 miles - about 45 miles of freeway at 55 mph and the rest around town. SG readings indicated about 40-50% SOC. My driving style is also 'modest' - try to pull 80-100 battery amps in cruise and accelerate/hill climb at 180-200 amps.

I don't yet know how it'll perform in our 'winters' of lows in the 40's.

edit - here's the EValbum page
http://www.evalbum.com/2358

[jyanof]

Originally Posted by MPaulHolmes

That makes sense. Maybe I should mail him another microcontroller. Man, I need to get a bootloader on it.

Joe, are you still seeing 480 amps (or whatever) with the software right now?

I think it'd be a great thing to try.

I am - 478 right on the nose every time. Guess it's tough to tell how each individual controller comes out?

[MPaulHolmes]

I need to get an ammeter and shunt. Where did you get yours? When I see the "current" from the microcontroller, it's a byte from 0 to around 211, but I don't know for absolute certain what that range really is. I need an actual calibrated shunt and ammeter. It would be nice to compare multiple controllers.

[jyanof]

Originally Posted by MPaulHolmes

I need to get an ammeter and shunt. Where did you get yours?

This was the cheapest place I had found:
500A, 50Mv Shunt - Shunts @ AltE

Ends up being 10A per mv. I bought a cheapo panel meter on ebay for $10 (that I had to fine tune to work), but you might be able to use a voltmeter on the mV scale.

[vinny1989]

Originally Posted by bennelson

PS: I also FINALLY found my ELECTRIC CAR CHARGING ONLY sign today. It's only been mixing about 6 or 7 months. Turns out it was at the church where we held our Earth Day Alt. Auto Show. I had been past it several times, but only saw the back of it. It blends right in with all of the other "real" signs there.

One guy said that nobody has parked in that space for months because of it!

Thats really funny, Made my day!

Glad you got the sign back though.

[bennelson]

I added two more batteries to the car today.

To do it, I had to put the old bed frame rack back in, spanning the trunk spare tire space.

At 96 volts, the car is a bit peppier. I can hit 55 mph, although it sure seems like a waste of amps to get to and maintain that speed.

I took the wife out to dinner tonight, and noticed the extra voltage was nice for a particular stretch of higher speed road.

Also, the throttle seems to act a little different at 96v than it did at 72. Maybe there is something to what you guys were saying about code.

I know NOTHING about electronics, but Tom (of the 300V AC Dodge Neon Project) knows all that stuff. He mentioned to me today that he could take a look at the controller and that we could "tweak it up".

Also, Tom was able to get a different set of batteries for his Neon - a full matched set. Which means his old batteries MIGHT be available for my car. Why I am interested is that they are group 24 batteries. Mine are group 31. The difference in LENGTH of batteries might allow more group 24s to fit in my car than group 31. For example - 4 group 24s can fit in the radiator space, but 2 group 31s can barely be squeezed in there.

I have also seen a Geo Metro with a rear seat box with 7 group 24s in it. My seat box only holds 5 batteries right now.

Hmmm.... Sounds like I COULD do 12 group 24s for 144V AND keep my trunk! Even 120V would be pretty slick.

More than anything, I want to improve my range. Seems like the best way to do it is to increase system voltage. Better top speed is just a handy side-effect!

PS: I also noticed that the Open Source Controller DOES cause a little interference on my radio. I only get one FM station, because my radio antennae has been "aero-modded" off. Okay, okay, it was broken off when I bought the car, and the one station I get is the only one I really listen to anyways.

Anywho - it's not bad, it's just a little static, most noticeable when pulling away from a stop. Any ideas on minimizing the noise in my radio reception?