Tango Cars

Friday, April 30, 2010

Tango passes Automotive X-Prize Shakedown Event at Michigan International Speedway

There were lots of issues to contend with up to the end, but got through with flying colors.

Consumer reports had something to say about our achievements:

http://blogs.consumerreports.org/cars/2010/04/automotive-x-prize-shakedown-continues-drama-ensues.html

We have a brand new LiFePO4 pack and had a cell failure. We had the pack out, which was rather easy, having a lift and using the removal kit that I brought along.

After bypassing the cell, I ran the endurance run today on the MIS test track. It was very rough road, over two miles of every kind of turn and elevation change. In our group, The Tango was the only one completing the full 40 miles without having to pit. I lapped a bunch of cars and never got passed. In fact, I had the second fastest time of all competing teams. I ran a fast lap of 2:05.2, only 3 seconds slower than the factory 5 car that ran a 2:02. They kept motioning me to slow down, but I was having way too much fun. I was drifting a turn right in front of the judges and using up every last inch of track. The track was wild--like an old torn-up country road. I was still developing my line up through the last lap--there were so many odd patches of road to contend with. The Tango handled them great though. I had the current set to half, at 1,000A to be nice to the battery, and didn't even accelerate close to that potential. I could easily have beat that Factory 5 car if I had pushed it.

Yesterday I was at a press conference in Lansing where I got to introduce the Tango to Michigan Governor Granholm. A lot of press was there, and they had the Tango right at the stage.

Some news on the event:

http://www.wlns.com/

Then go to Clean Car Competition under videos.

Thursday, March 25, 2010

New Record Set: 122.5 miles @ 60 mph; 249.8 Wh/mi with 30.6 kWhrs

While doing a mileage run, I shot this photo of the Tango's shadow.

This nicely illustrates how easily it fits in half a lane.

The new Headway LiFePO4 pack is now delivering over 30 kWhrs under freeway driving conditions at 60 mph. This morning my wife Alice and I drove 122.5 miles on a charge on relatively level freeway (a couple hundred feet of elevation change). This worked out to 249.8 Wh/mile. The Progressive Automotive X-Prize requires 100 miles of range and an equivalent of 100 mpg. This is defined as MPGe. The conversion used is 32.82 kWhrs = 1 gallon of gasoline. This means that we need to achieve 328 Wh/mi or better to qualify. This is as measured at the wall receptacle, so charging and battery inefficiency must be considered. A couple of days ago, we drove 80.7 miles with a 252.75 Wh/mi reading from on-board instruments, while the kWhr meter on the wall read 24 kWhrs. That works out to 297 Wh/mi. That's an 85% efficiency. After equalizing the cells all night, the meter at the wall read 25 kWhrs or 310 Wh/mi, which is still well within the requirement--all this with an extra 200 lbs of lead ballast and a second passenger.

With 100 more volts and much less sag from the battery pack, the Tango is now much much faster than with the lead-acid batteries that have been used for all events in the past. We haven't run the 1/4 mile with the Headways yet, but look forward to writing that post.

Sunday, March 14, 2010

Range Update on Headway LiFePO4 Battery Pack

Today we just drove the Tango 103 miles, mostly at 75 mph. Range is increasing slightly as another cycle is on the battery. Following is the status from the BMS at the end of the trip.

Tuesday, March 9, 2010

Tango with 32 kWhr pack of Headway LiFePO4 cells goes 108 miles on a charge

Because it was cold and snowing at times, and because this was only the second cycle on the battery, we only used 28 kWhrs out of the 32 kWhrs that the cells are rated for. The Tango used 260 Whrs per mile at an average speed of about 60 mph on highways with about 400 ft of elevation change. The Elithion BMS gave the following status at the end of the trip.

STATUS OF PARALLEL BATT #0: OK

Cell vtg [V]: 3.05 min(# 46) 3.14 avg 3.18 max(# 20)

Total vtg [V]: 314.7

Cell bd temp, all [C]: +23 min(# 14) +29 avg +35 max(# 46)

Cell bd temp, load off [C]: +23 min(# 14) +29 avg +35 max(# 46)

Cell blk res [mOhm]: 25.4 min(# 0) 25.4 avg 25.4 max(# 0)

Total res: 2540 mOhm

Loads on: 0 (Not balancing: avg voltages below min bal vtg)

Cell boards: 100 (# 0 ~ # 99), all reporting

Banks: 12 (# 0 ~ #11), all reporting

This Headway pack has 1,000 cells mounted in parallel groups of 10, and 100 blocks in series. These were then packaged into 12 modules as pictured below.

There is approximately 200 lbs of lead added to the bottom of the battery box to make up for the lighter weight of the lithium cells. Some of this is visible in the photo below.