Category: EV Build Log


Rush

Why Rush? Well, because I’ve got some Moving Pictures. Here’s some bench test vids of the controller for your enjoyment!

 

 

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It LIVES!

It LIVES!

So after realizing I didn’t need to fight with the USB-Serial adapter, because I had a laptop with an on-board port next to me, I fired it all up and DING! Win. Now, to fix the power LED and assemble it all…

Still Alive

This was a triumph…no, it really was. After this long dark age, there’s something to report and should be (slightly) more regular updates from here on out.

Programming via USBtinyISP

I managed not too long ago to finally get a programmer kit from Adafruit to build a USBtinyISP programmer for loading code onto the ATMega168 microprocessor that is the ‘brain’ of our EV motor controller. After a little research and some trial and error, I think I’ve got our control board programmed.

We’ve got a copper bus bar coming on Tuesday that’ll get cut to make the 3 main bus bars of the controller – 3/8″ x 3/4″ x 45 1/2″ long, 99.99% pure electrical conductive copper. It’ll get cut in thirds to make the 3 bus bars of the controller. Once all this is up and ready, we’ll only need a capacitor bank to begin testing the controller on the go-kart!

 

 

RT @300mpgben: One whole summer of converting a car to electric, condensed down to easy-to-watch short videos. http://www.youtube.com/playlist?list=PL2077F803C62CF0E5 via @YouTube #ev

 

Ben is an awesome guy to talk to. He’s certainly inspired me, and his work is amazing.

I know it’s been a long time since there have been any updates, but fear not! I and my compatriots that are working on the project are still here. I’ve changed jobs and have a smaller commute, so hopefully I’ll have more time to not only post updates about our progress, but also time to make progress as well.

We’re going to keep going with the Jetta, even though it needs some body work. I’ve got easy access to a shop with all the necessary utilities to make easy work of the needed repairs, so that’s not something I’m concerning myself with very hard. It does mean that we need to totally strip the interior however – seats, carpet, and all.

At least it appears to be easy work to start with that can be done in small pieces! One seat here, one seat there, feels like progress – even if it is small progress.
We’ll be in touch!

Over the weekend I managed to find time to get out to the garage for some EV time. The other week my cousin brought the 1997 VW Jetta donor car up to my garage to get it out of the way where it was as well as get it stored for working on.

A little worse for wear from sitting, but not really beat to pieces. I pop the hood and what do I find but some of those gremlins that everyone talks of!

It was getting dark when I took the photos and didn’t have my real camera with me. The girls had fun seeing what the car was like in its current condition. I wanted to open the sunroof and take some pictures that way, but I ran into a problem: I knew the battery had been removed, but the battery cables were gone too!

That was mid-week. Saturday I found some time to get out there with Jay and Scott, my buddies that are also in on this project. After a bit of contemplation and shop talk, we decided to quick-rig some wires with a small battery I had so that we could open a window or two as well as the roof. It’s hard to communicate easily from inside the car to outside with all the doors shut and windows all the way up.

Well, we get everything wired up, and get it all ready to plug in. Connect the last wire, and

BRRRRRRRRRREEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEP!

Jay and I both jumped (Scott hadn’t gotten there yet). So we unplug the horn and try again. BREEEEEEP! Sound is coming from under the fender near the firewall! Oh joy, it’s got a car alarm! Scott shows up, we ponder what to do, and decide to pull the fuse for it. I grab a flashlight, stick my head under the dash, and there’s nothing. The fuse box was empty! Read the manual, not really of much help. It does say that the sunroof is not part of the alarm. So we put a fuse in #21 for “body electrical, interior lights” and re-connect the battery. One beep! and then just the door chime. Yes! However, new problem: Sunroof still won’t open.

We move on to getting the car lifted to pull the rest of the exhaust off. Got the front end up on stands no problem. Crawl under the middle to see about taking the exhaust pipe apart, and I see a sight I didn’t expect that makes my heart drop:

The Rust Fairy came and visited the car while it was parked. I’ve heard mention of the Rust Fairy, and I’ve seen little bits of what happens when her fairy dust falls or her pet Tin Worm comes through, but nothing like this before.

A two-foot long gash in the floorpan, as well as a 5 inch diameter hole where you can reach up and touch the carpeting from underneath the car. Not sure what to do, and the mood ruined for all of us, we called it a night and closed up shop.

Jetta Engine Pull

Good Morning! It’s been a long, looooong hiatus for me. I’m not dead, and neither is this project – quite the contrary! I’ve just been both super busy and out of the loop for a while.

However, there is now progress to report! On Saturday, I went out to the family machine shop and my cousins and I pulled the engine out of the donor car – a 1997 Volkswagen Jetta. It was running when it was parked last fall, but winter and critters got to some of the wiring. No big deal, we won’t be using  most of it anyway!

My photos didn’t come out as nice as I had hoped. It’s hard to try and take good photos with a point-and-shoot in a dark-ish area when you’re trying not to get the camera dirty. We did have some trouble, but most everything came out pretty clean. The car is all askew in the last photo due to a bad tire, the fact that it’s not sitting level, and that there’s practically no weight over the front wheel. It may be kind of a beater, but it was free – and even now I smile when I look at the picture and think “This is MY OWN electric car.”

Photos by Jeff Haskell, Aug 13, 2011

Vodpod videos no longer available.

EV Build Night #1

There are four of us who will be involved in the project of building this EV. Last night, three of us – Scott, Cory, and myself – managed to get together for a little bit and dig in.

We managed to get all of the electronics off of the treadmill. The motor I had previously taken out; however, the controller(s) and power supply were still attached. With everything yanked out, we took stock.

Power came in from the AC wall outlet to the power supply, which made DC for the user interface board and the SCR motor controller. Our goal was to determine if the SCR board ran on straight DC, and if we could power it directly from a battery. Yes it does! No, we can’t use it! A total bummer, but it was nice to spend time in good company not worried about life, school, or other concerns.

SCR works by chopping up the sine waveform of AC power and feeding on portions of the wave to the motor. DC doesn’t have waves like AC does, so it didn’t work when it was plugged in on battery only. So now, we’re still in search of another treadmill that has a PWM controller. PWM functions by turning on and off the DC power (called a Pulse) and adjusting (modulating) how long the power is on for (width). Once we have one of those in our possession, we’ll be able to make REAL progress.

Battery Math

When it comes to EV building, you can have the best of the best of everything – aerodynamic body, great motor, excellent controller. However, when it’s all said and done, you’ll sink or swim depending on your batteries.

I’m not going to get into types/sizes/brands here; this is more about the preliminary calculations than anything else. There are some general rules of thumb when it comes to powering an EV:

  • Voltage = Speed. It’s not quite that simple, but close enough for basics. The more voltage you can provide to the motor, the faster you’ll be able to go.
  • Amperage = Acceleration. Whereas voltage enables the motor to turn faster, amperage is what allows the motor to turn when a load (in our case, a whole car via the driveshaft) is applied.

Also to note is the fact that the lower the amperage you ask the batteries to output, the longer they can output it for. This means you either accelerate VERY slowly, or…increase the voltage!

How does that work, if voltage equals acceleration? It’s a transformation of Ohm’s Law. Ohm’s Law states that the current, I, through a conductor between two points is directly proportional to the potential difference, V, across the two points, and inversely proportional to the resistance, R, between them:

I=\frac{V}{R}

Current is amps, “Potential Difference” is volts, and the resistance is the load/work we want the electricity to be doing – realistically, the wattage. So to simplify, we end up with the following replacements and transformation:

\mbox{Amps}=\frac{\mbox{Volts}}{\mbox{Watts}}              THUS             \mbox{Watts}=\frac{\mbox{Volts}}{\mbox{Amps}}

So, for the same amount of power output (in Watts), I can have more amps and less volts, or more volts and less amps. Less amps = good things, so we keep the voltage as high as reasonably feasible.

I’ve got 64x 12V, 7.2Ah batteries. They’re small, both in electrical capacity (amp-hours), and in physical size. However, there are SIXTY-FOUR of them.

That’s the same as 8x 96V 7.2Ah batteries.
8x 7.2Ah = 57.6 Ah total @ 96V
96V * 57.6Ah = 5529.6 Wh; 5.5296 kWh

There are 5.52 kilowatt-hours of electricity in my battery pack. Electric cars use, on average, 250 to 350 Watt-hours of electricity per mile driven.

Let’s use 300 Wh/mi for now, with an 80% ‘Depth of Discharge.’ That’s how much of the total power you use out of the batteries. If you 100% discharge a battery, it’ll basically kill it permanently. 80% is a “safe zone” of discharge for lead-acid batteries, so let’s start there.:

5529.6Wh * 0.80 DoD = 4423.68 Wh @ 80%
4423.68Wh / 300Wh/mi = 14.746 miles

so yeah, we’ll call it 15 miles range at 80%. Most likely, with used batteries like mine, it’d be safer to only go to 50% – which works out to 9.218 miles. The batteries I have are extremely small! Most EV-ers have batteries that are 20 to 60 Amp-hours EACH! This is why we’re starting with the go-kart.

So I was out on a PC house call tonight, fixing some systems and returning one that I repaired. I was talking to the guy, who happens to have a landscaping business. I asked him if he knew of anyone who might have bigger size electric motors, or an electric forklift. He said he knew someone with an electric forklift with a bad battery pack! Couldn’t remember who or where he saw it, but the question is out there. I’m hoping to hear back. If not, oh well; but at least I put it out there.