Monday, August 23, 2010

Burnout Mode Engaged

After realizing that we had spare tires, all I could think about was doing donuts in the elEVen. Having never done a donut in the car, I decided to practice before hand. It looked more or less like this:

One difference is that I wore a helmet. As always, safety first.

In that same vein, we double checked all of the wiring and structural members to make sure that no short could occur, that all wheels would stay on the car, and that no oil would leak.

In our inspection, we found something wrong with the SCU. After 3 hours of debugging, we diagnosed the condition as dirty connectors between the motherboard and one of the cards. After cleaning the connectors, we fired up the SCU and sure enough the problem had been resolved.

We closed the SCU back up and soon we began the tedious process of remounting it back in the car.

The SCU was designed to fit into an electric school bus which has tons of space to mount components. Our Mercury Milan is a little more cramped making the mounting and unmounting process a more difficult. It is a three person job, with one person manning the hoist, another person making sure that nothing is in the way and the third under the car that aligns the SCU into its mounts.

Once every thing was back in, we went for a little drive up and down the street that our shop is on.

What follows are some pictures that we took before, during and after the first drive of this summer of the MIT EVT elEVen.

Thursday, August 12, 2010

elEVen Status Update

The heat is rising in MIT's Electric Vehicle Team shop. After late nights of soldering, countless breaks for Monster, and hours of tedious coding, our Mercury Milan conversion - the elEVen - is nearly street ready. The elEVen conversion and rapid recharging were delayed due to a problem with the motor controller, as was discussed in Stephen’s earlier blog post. While that problem was being resolved, the team wasted no time in starting other projects to increase the safety, comfort, and robustness of the car. These projects - including the battery cooling system, the mount for the charger, the charging adapter, the motor controller wiring box, and all of the internal communications - have either been finished or are nearing their respective ends to where the whole car can be assembled. Once the car is put together we can begin working on rapid recharging, but until then, the engineers in us are eager to get the elEVen running and on the road.

Here is our status on each of the elEVen projects:

Thursday, July 29, 2010

A New Cell Cycler

Recharge your electric car in less than 10 minutes! This has been the dream of many current and future electric vehicle owners. But imagine the batteries in your car could only handle this rapid recharging maybe 400 times - about the lifetime of a laptop battery, charging at a normal pace. Let's do some math: 100 miles (the range of the Porsche 914 BEV) x 400 cycles = 40,000 miles per car. Who would want a car with a battery pack that only lasted three years? [1] Not EVT! We wanted top of the line batteries that could handle our abusive rapid recharging and put up a fight for an acceptable number of cycles. Just in time, we came across A123, one of the industry's leaders in battery technology.

A hundred battery boxes later, we were ready to put our A123 cells to the rapid recharge challenge. In order to test our new batteries, Lennon Rodgers set up a station to rapidly cycle - charge and discharge - an A123 cylindrical 26650 battery, pictured here. After cycling the cell repeatedly, he hoped that even with the deteriorating effect of rapid charging on any type of batteries, the cell wouldn't lose much of its original capacity. His results are shown in the graph below.

Excitingly, after almost 1500 cycles, the cell barely degraded. So, 1500 cycles corresponds to 150,000 miles which is nearly the average lifetime of a car. [2] This is much more reasonable for a commercially marketable battery pack. Though this result is exciting for the possibility of rapid recharge technology, only one cell was tested which does not constitute a statistically significant sample size. Therefore I have spent the last few weeks setting up a new cell cycler. This cycler will rapidly cycle the same type of battery, a cylindrical 26650 battery and hopefully support the results from the first test.

Here are some technical details of the circuit. The cycler has two parts connected
to the battery through a set of relay switches: 1) a power source used for constant current charging at 10Amps and 2) a .25Ω resistor through which the battery can discharge. During the entire cycle, the battery temperature, voltage and current as well as the temperature of the resistor are monitored and constantly checked for dangerously high or low values. The data is sent through an Arduino-controlled circuit to a wireless ioBridge module which allows us to remotely upload data to monitor the status of the battery and keep a running chart of its capacity.

After a brief setback in which I killed a cell (thank you to Shane Colton for his assistance in soldering a new replacement cell), the cycler is up and running. In the time since it was turned on last Friday, July 30th, it has undergone over 300 cycles. It will take about a month to complete the goal of 1500 cycles, but the cycler is well underway and showing promising results. Stay tuned for the results on the second cycler test as a step on our way to rapid recharge technology.


Wednesday, July 28, 2010

Manzanita Mounting Frame

The project I have been working on for the past week or two has been fabricating a mounting frame for our charger. Though it may appear so from the outside, charging a battery pack like ours is not as simple as plugging it into the wall. The power first has to go through an intermediate stage before it can charge the batteries. For this intermediate, we have the Manzanita Micro PFC-50 (seen below). It is a charger that can handle anything from regular charging all the way up to very rapid recharging.Since the elEVen's current battery pack is in the trunk, it would be ideal if the charger could be in there with it. However, there was very little room left in the trunk with the massive battery pack and new cooling shroud, so I had to work within the remaining space. The only place the Manzanita would fit was above the cooling unit. Keeping the dimensions of the trunk in mind, I came up with a design in Solidworks. The whole frame would be welded together, and the Manzanita would be easily bolted on. Here is a preliminary design I made.
After double checking everything to make sure it would fit, I began cutting lengths from a bar of hollow, square cross section steel using our cold saw. I then drilled the mounting holes in them, and handed them over to Pete, our designated daytime welder, to weld together. While he was doing that I cut four small triangles out of steel plate and put a hole in each of them. The idea was to weld the small triangles to the bottom of the trunk, and then bolt the mounting frame onto them. This would allow easy removal of the whole frame while having a small permanent footprint in the car and allowing for the cooling shroud to be easily removed if necessary. Once Pete finished the welding, he hit it with a shiny black paint job, and it was done. It fits perfectly too, have a look.

Friday, July 23, 2010

Wiring Party

These past few weeks I've been assigned to rewire the breakout box. Before it was a colossal mess but it did what it was supposed to, it got the car rolling.

This time I designed a much more compact wiring box that also incorporates the relay box and other small circuitry. It has one 0.5" cable that goes from the System Control Unit to the breakout box and it does everything else from there. It uses a d-subminiature as an input with two db-25 and two db-9 outputs. It is completely customizable to allow additional ouputs. It has a large 60 signal breakout board that centralizes all the signals that are going to the drivetrain. All of this is done in an enclosure about the size of just the original relay box.

Saturday, July 17, 2010

Street Racing

So I was driving down the road the other day in my all electric Mercury Milan when a Tesla Roadster pulled up next to me. Feeling a little confident about my car, I challenged the Roadster to a race. Within 4 seconds, I was already at 180 kph! I blew that sorry Tesla out of the water!

Here's proof:

That's right, I did it with no fuel. Or battery charge. And I left the parking brake on. And my car was telling me to pull over. It's because I was being too awesome.

What? You think I'm lying? Okay! Okay! You caught me.

The slightly more interesting story is that I have started to integrate the CompactRIO, which I mentioned in my last post, into the car. As a test to see if it was working, I decided to control the car's speedometer and satisfy my need for speed at the same time. The next step is to try to convince the car that everything is okay. I hope to get this done by the end of next week so that the car will be ready for inspection and license plates following soon after.

Things are really starting to come together and I hope that you check back regularly for new posts about our work on electric vehicles.

Thursday, July 15, 2010

A Luxury Vehicle - The Little Things

The little nuances are important when working with a luxury car (something you don’t think about until you are trying to maintain a luxury vehicle). The Porsche is a completed project that team has worked on in the past. Not only is it a beautiful car, it exhibits electric cars as a viable option. However, it is important that this luxury car look and run like a luxury vehicle. At the beginning of the summer, Pete one of the guys on the team noticed this creaking sound and decided it was creaking due to the suspension (the linkages, shock absorbers, and springs which connect the wheels to the vehicle). The decision was to look at the bushings on the suspension and make sure that they were well oiled.

This doesn’t seem like a big deal, but it can take up a lot of time. It requires moving the car and putting it on the lift. Then, we needed to start taking apart the suspension. This proved to be quite the task, in fact we ended up pulling out penetrating oil in order to disentangle rusted parts. We finally were able to pull the bushings out. We cleaned them thoroughly and spread oil on them. We than began putting all the suspension pieces back into the Porsche.

Good news – We got rid of that creaking sound, and I finally became a grease monkey (or at least I now consider myself in the club).

Thermal management of the battery pack

One of the projects I'm working on this summer is the thermal management of our battery pack during rapid charging. Charging the battery pack in less then 11 minutes generates a lot of heat within the pack. To remove that heat and cool down the cells during rapid charging I've designed a cooling shroud to force air through the closely spaced battery cells inside the pack. To overcome the pressure drop inside the pack we're using three centrifugal blowers.

Wednesday, July 7, 2010

Breanna's Blog #1

After much resistance, I have decided to finally begin my blogging for the summer. My blog posts might not seem quite as relevant as other team bloggers, but hopefully they will give a bit of insight into how our team works and functions as both a research group and student group.

Despite majoring in Course 2, before this summer began I lacked the hands on experience that is associated with such a degree – basic shop training. The first thing I want to post about is how I learned to use this equipment.

In the beginning of the summer, Steven Lam a fellow EVTer was designing and constructing an oil sump. In order to build specific sides of this oil sump he needed to use a milling machine. When Steven was working on it, he took me under his tutelage and taught me how to use the milling machine. By the end of this instruction, I knew how to change the mill bits for the various sizes and types of holes needed to cut into this aluminum and understood how the various planes of the mill worked and how they could be used to finish creating a design.

However, this lesson didn’t even begin to cover everything you need to know to use the milling machine. I needed to gain a lot more knowledge and experience before I could use the machine by myself, without being under some supervision. The options were reading a manual, helping my fellow EVTers machine stuff, and/or attending a machining class. Luckily, our team had a shop training class that weekend. After a 3 hour training on the mill machine, I felt comfortable to use a machine basically by myself (of course, I would still need to appeal to one of the senior members on my team to double check my set-up before I began to mill). In addition to this newfound skill, I also had joint ownership on “EVT bling” with Dianna.

SAE J1772

Normally, when your car runs out of fuel, you pull into a gas station and fill up. Most cars run on regular, though some cars run on premium, diesel, etc. If you have an electric car, you probably have to drive home to charge up you vehicle, and likely use a custom made charging port for your car that you plug in to a normal wall outlet. Well, all of that is changing. Enter the SAE J1772 standard outlet.

This plug will be the new “regular unleaded” for EV’s. It is being used on the new Nissan Leaf, the Chevy Volt, and even Tesla is likely to take advantage of it. On top of that, charging stations are being built around the country by several companies, most of which will use the J1772. Having a uniform standard is important for large scale production, and is a necessary step if EV’s are to become mainstream.

This may sound great, but here’s the most exciting part: we’re getting our own J1772 port. I have been in contact with Tim Rose, the managing director of REMA EV, a company which makes electric power connections. They have been kind enough to donate the port along with the appropriate connectors, and if all goes well we’ll be getting one for the elEVen very soon and one for the Porsche in a few weeks. When it arrives I will be figuring out a way to install the port where the fuel filler cap used to go, and soon after we will hopefully have a way to charge the elEVen’s batteries.

Thursday, July 1, 2010

Talking to Batteries

EVT has worked a lot with the A123 26650 cells: we've cycled them, rapid-charged them, drilled into them, built packs out of them, all in a few semesters. At the beginning of this summer, we even charged the whole eMoto pack in 11 minutes and 30 seconds! This spring we got a shiny NEW toy: an A123 Prismatic Module.

The A123 prismatics have a much higher energy density than the 26650's and they come in a sweet pack arrangement. We have some single cells that we've been testing, and Lennon and Shane have built a rig to cycle one prismatic 1,500 times at a 6C charge/discharge rate. More updates on that later.
For the past few weeks I've been working on using an Arduino and an MCP2515 chip to talk to the BMS built into the Prismatic Pack. It talks over a CAN network, much like the systems in the Porsche or the elEVen. I've found that using the Arduino allowed me to start communicating in CAN easily in only a day or two, and now I can intelligently talk to the module, polling it for voltage and SOC information and telling it to actively balance itself. In the picture you can see the Arduino board sitting on top of the module, and the cable running over the top that connects the two together. The next step will be to output the battery data to a screen and create a system for talking to multiple packs, like we'll have on the next EVT motorcycle.

Say hello to the newest member of the EVT fleet, a blue Lifan motorcycle. This is the same frame that eMoto was originally converted from, and soon it will hold the above prismatic module and a shiny new motor. Last week Lennon, Randal, and I traveled down to Providence and bought the 2-year-old gas motorcycle from a guy who had never ridden it. When we returned, Randal and I ripped the combustion components and twelve volt system out (the lights and fairings had already been removed) and Will has begun designing a new frame to mount all the electric components. Look out for updates on the new frame and another new addition to our team.


Monday, June 28, 2010

Trip to Maryland

This past weekend Adrian, Erick, and I took a trip to Maryland to pay Satcon a visit.

At the beginning of the summer we blew out a fuse and damaged a few components on our motor controller. We were powering it with a 12v charger instead of a regulated 12v power supply and had inadvertently given it 20 v.

We gave the guys at Satcon a call and they told us to bring it down. After an hour of probing they were able to narrow the problem down to the relay card. Apparently a diode blew and started shorting everything out. Satcon guys found another relay card in storage, robbed a few components, and then put everything back together for us. We crossed our fingers and turned it on. Luckily for us the laptop was finally able to communicate with the controller.

Let's hope it still works.

The Summer Team

Now that summer projects are well underway, the team is on-site Monday through Friday, and often on the weekends. Check out the team profiles at to meet the engineers that are working hard to finish converting the elEVen this summer.

Friday, June 25, 2010

Work on the CAN network

Hey Everyone,
My name is Erick, I'm a rising Senior in the Aero/Astro department and I'm pretty awesome. But enough about me, let's talk about what I've done.

I am working on the CAN network for the elEVen. In a few sentences, the CAN network is composed of nodes and communicates between nodes using 3 wires. Those wires are named CAN-High, CAN-Low and ground. When the voltage difference is zero, that is understood as a bit with a value of one and conversely, when the voltage difference is not zero, that is understood as a bit with value of zero. Do this thousands of times a second and you start to get a serious amount of traffic going through these three wires.

As a learning exercise, I am practicing with the Porsche 914 that we have already converted and am putting a few finishing touches on the interfaces. In order to tap in to this network, National Instruments has hooked us up with a CompactRIO with a CAN Module. I installed LabVIEW and have been messing around with it for a few days. After finally figuring out why I couldn't connect to the cRIO and the touch panel, here is the result of a few hours of work:

Once I become more familiar with LabVIEW, I will be able to receive, parse and send CAN messages. This will allows us to communicate vital messages, like the state of charge of the battery pack, vehicle speed, as well as slightly less vital messages, like what radio station you are listening to.

I'm excited to be working with the Electric Vehicle Team this summer and looking forward to all of the projects, which you will hear about through this blog, come to fruition.

Oh yeah, make sure to follow us on twitter!

Thursday, June 24, 2010

elEVen- Summer 2010

Hey everyone, EVT is back at it again this summer working on our 2010 Mercury Milan all-electric conversion.

Last summer the team was able to successfully remove the vehicle's original hybrid drive system and install a 250hp oil cooled 3 phase AC induction electric bus motor (courtesy of Satcon) along with a 20kWh A123 prototype battery pack consisting of 2,700 A123 26650 cells (many many thanks to A123). The elEVen first moved under its own power last August, but the conversion was far from complete.

This summer we have a new crew ready to pick up where last summer's crew left off on the elEVen. The two main goals for this summer are getting the battery pack ready for rapid recharging and making the elEVen street legal. To do this we will need to install an air cooling system for the battery pack, design a charging port capable of handling the huge power flux that rapid recharging will require and interface with the BMS (battery management system) motor controller and the car's own CAN networks through a Texas Instruments cRio programmable automation controller. There are also a whole bunch of other small projects that also need to get done so that the elEVen is the safe and reliable glimpse into what might be the future of automobiles.

Look for more blog posts about what everyone is doing soon.

Monday, June 21, 2010

Troubleshooting the elEVen Motor Controller

About two weeks ago we tried to communicate with the elEVen motor controller but couldn't get a response forcing us to remove the motor controller from the car to figure out what was wrong.

We laid out the motor controller and all the components it interfaced with on a table in our workspace, first troubleshooting the electronics external to the motor controller. After not finding any problems in electronics outside the motor controller we suspected something was wrong inside.

We went through several troubleshooting procedures outlined in the motor controller manual but still couldn't get it to work. Fortunately for us, the engineers who designed the motor controller were helping us along the way. We thought we had narrowed down the problem to a electronics card inside in the controller that provided the controller with power. After inspecting the card and not finding anything wrong with it we've decided to drive to Maryland to get help from the engineers who designed the controller. Updates on our trip to Maryland coming soon.

Tuesday, March 9, 2010

A rapid charging electric motorcycle

Over the last few months we've been working on a rapid charging electric motorcycle. Here's a picture of the full setup:

We made our own custom battery packs, charger, etc. It's using a battery-to-battery charging scheme.
We wrote up our full design, cell cycling results, etc. and have submitted it for journal publication. Hopefully we can release all of this information soon - very exciting!