Details

Published: 07 October 2016

1st Test Drive!

The last item on the punch list for the first drive was calibrate the brake pressure sensor.  I had spent a lot of time and effort in getting that sensor mounted near the rear brakes that I detailed in an blog from last year named Almost Rolling.  The pressure sensor is used to indicate braking which will signal to the GEVCU to command the DMOC/Siemens into regen to slow the car.  Because the regen torque can be set to a very high level almost no brakes are required.  But the transducer has to signal the brakes are being applied and the brake lights come on. The calibration procedure is very simple, just take a reading with the brakes off and then with the brake pedal pressed.  Unfortunately when I press the brake pedal the pedal went to the floor with no resistance.  Somehow air had gotten into the brake line and the brakes would need to be pressure bled again.  Previously I had a real problem pressure bleeding the rear brakes.  I could not get a good flow of brake fluid to remove all the air in the line.  Something was preventing the flow.  Besides the master cylinder the only other component in the brake line is the proportionating valve that is used the regulate the pressure in the rear brakes so they don't lock up. These types of valves were used before ABS was developed.  I was concerned I might have to replace that valve because of the rear disk brakes I had installed.  They would brake stronger than the drum brakes that the car came with and might lock-up with hard braking. But I also increased the braking strength of the front brakes too with new rotors and pads.  I thought I could just see how the brakes would work without changing it.  With the brake bleeding problem it became necessary to replace the valve.  I installed an adjustable valve from Wilwood brakes.  That solved the brake bleeding problem but I still could not get a good brake pedal.  The only thing left to check were the rear brake calipers.  I had read online that some new calipers need to be bench bled.  Before going to that effort I unbolted the caliper from the hub, with the flexible brake line still attached, I rotated the caliper so the bleed nipple was straight up. Using the pressure bleeder I found both calipers had a lot of air in them, especially the right rear. By moving and rotating the caliper I was able to get all the air out. Once I was able to do that and bleed the rest of the brake system once more I got a good stiff brake pedal and I was able to calibrate the brake sensor.

Just when I was in the process of getting the car ready for the first test drive I discovered the GEVCU was not sequencing the high voltage contactors correctly and the DMOC would not spin the motor.  It seems the GEVCU lost some of its configuration data.  When I was trying to figure out what was going on I discovered the contactors were fused because I could measure high voltage at the buss bar when the car was off.  That means they do not switch the high voltage and are permanently shorted.  They can be damaged when a high current pulse happens.  The DMOC has a large capacitor bank and when not charged looks like a dead short and will take a large current pulse from the battery pack if not controlled.  In my design I use a precharge resistor to limit the current inrush.  But that only works if the contactors sequence correctly.  With the GECVU loosing configuration data it must have caused the contactors to fail because I had bench tested the contactor box many, many times.  I even found a problem with the GEVCU MOSFETS that would have lead to this problem. But I fixed that circuit issue on the GEVCU I am using and had tested it extensively.  Unfortunately the contactors are not easily replaced in my build.  They will have to be replaced but since they are fused they should conduct enough current to move the car.  To get my first test drive I built another precharge/contactor circuit that runs off an Arduino Uno processor and relay shield.  Once I installed that and verified it was working I was ready for the test drive.

Finally I was able to get the car off the jack stands and back it out of the garage under EV power.  That is the first time the car has been out of the garage since January 2014 when I pushed the car out of the garage and pressure washed the engine compartment after the internal combustion engine (ICE) was removed.  I drove the car out of the garage this time to finish painting inside the engine bay and the area where the hood is mounted.  After the painting was completed I had to drive the car back into the garage and wait for the paint to dry a couple of days so I could mount hood. I mounted up several GoPro cameras around the inside and outside of the car. After that I went on the first test drive. The car drove great!  Very smooth and responsive!  I did not drive it further than around the block a couple of times because of the fused contactors.  Before going on the test drive I weighed the car.  On this website in my design section I showed after all the ICE components were removed the car weight was just 1776 lbs. Now with all the electric vehicle components the car weight is 2860 lbs and the weight is nearly 50/50 front to rear (48/52). If the rule of thumb for energy use holds then the 320i should use no more than 286W/mile. My Leaf used to do better than that and the Leaf was a heavier car.  The Chevy Volt I have now is a much heavier car but because it has such low coefficient of drag I have seen energy use as low as 250 W/mile.  Obviously the lower the number the further the car will go on a given battery capacity.  So with my total capacity at 3.5V charge being 26.6KW the 320i should be able to go 97 miles  - almost the full 100 mile design goal!  Of course how far the car will drive on a charge is dependent on so many factors, the most of which are how aggressive I drive the car and how fast I drive on the interstate.  The Volt does so well because of its aerodynamic shape, but the 320i is a bit of a brick so it will consume a lot more energy at highway speeds.

I still have to finish the carpet installation and install the passenger seat.  I still don't know what I am going to do with the rear seat.  There really is not much room in that car for the rear seat so maybe just a platform that protects the battery boxes would be good.  Something will have to be done with the contactor box.  I might just jumper over the failed contactors and continue to use the new contactor box in the trunk. I also need to fix the BMS board and find out why the instrument cluster is not working.  I tested that before I mounted it in the dash so all the cabling should be correct.  For the test drive I used my Samsung tablet to display the embedded website so I could monitor all the drive functions. Once all these issues are resolved I plan to fully charge the battery pack and take the car for a long drive to see what the energy use will be.
But there still is a lot to do before the car can become a daily driver.  I have some BMW badges that need mounting along with the "Electric" badges I got.  Have to make sure all the lights are working and then the car needs to be inspected.  I need to have the registration changed to show it is electric drive now, although on old cars like this they do not do an emissions test.  Mostly just mechanical and lights but that will put the car in the registry database and I will be able to get an EV license plate, if I want.

A video of the first drive and some of these other fun issues can be found here.

Or you can check out the prequel video to the first drive here.

Details

Published: 23 August 2016

Driving soon???

I took part of the summer off, going on vacation and spending time with my family so not much work being done on the 320i for the past three months.  I was able finish the dashboard and all the 12V wiring.  I installed the AVC2, which is a module for controlling the J1772 connection to the charger.  Back at the beginning of June when I was getting ready to go on vacation I had charged the batteries up to 30AH and 375V which is half capacity and a cell voltage of 3.2V.  I assumed with nothing connected and even the manual disconnect switches open that the battery pack would just sit there and stay charged and be ready for me to drive it when I got back.  Just a couple of weeks ago I wanted to test out the AVC2 connection and turned on the car.  I always check the JLD404 to verify the voltage and state of charge.  To  my horror instead of reading 370V the pack was only reading 77V!!.  That meant the batteries had been discharged to less than 1V!  Not a good practice for lithium batteries of this type.  Over discharge can cause large losses in capacity because the lithium gets tied up in the cathode material.  I do not know what caused the discharge.  The only thing connected to the batteries was the BMS.  The current leakage in the switches used in the BMS is only a few microamps at 800V.  At the voltages the BMS switches see the current leakage should be sub-microamp so it would take a long, long time to drain down 30AH ( more than 30,000,000 hours!).  Something else must be going on.  My biggest concern was the state of the batteries. I measured the voltage of every battery.  They were all around 0.6V and the lowest was 0.25V and the highest was 0.85V.  No battery was at 0V so the bottom balancing I did earlier might have saved all the batteries.  I removed one of the batteries from the front battery box and connected to my lab bench supply and charged it at 1A until the voltage was 2.7V. That did not take very long - about 60 min. I then could put the battery on my Powerlab charger - that charger will not work on batteries discharged to a low level.  I charged the battery at 10A to 3.65V and the battery looked just fine.  The charge curve was normal and the battery charge capacity was 64AH.  As received from CALIB the average capacity of all the batteries was 66AH so a very small loss in capacity.  The problem I had was with the Bursa charger for the main pack because it would not work on a low pack voltage so I had to charge groups of batteries up to 2.7V using the Keithley 2420 source meter I have.  Earlier this year I had used that power supply for bottom balancing some of the batteries. I have a program I wrote for doing the bottom balancing, which is essentially what I would be doing again.  I charged batteries in groups of 10 to 18 up to an average voltage of 2.7V at a 1A charge rate.  I carefully checked the voltage of all the batteries during this initial charge.  After all the batteries were bottom balanced I could charge at the Level2 rate with the Brusa charger.  Once again I charged the pack to 375V and 30AH and carefully monitored all the battery voltages during the charge.  Nothing looked out of the ordinary. I then finished fully charging the pack to 60AH and 413V.  Everything still looked ok, except one battery went to 3.65V when the average charge voltage as just 3.45V. I stopped the charge because that battery went to full voltage and I did not want to overcharge that battery, even though I will probably replace it. The question now is how did the pack become discharged in just a couple of months.  I know earlier from making measurements there is no leakage path to the car ground. I only measure capacitive voltage when I test from the battery peak voltage to car ground.  However, recently when I was changing out that battery in the front battery box that went to 3.65V during the charge I got a shock when I brushed against the battery box.  The battery box is grounded, but the batteries should have no reference to that ground.  When I measured from the last battery in the front box to ground I measured 53V, which should not be there.  I started disconnecting things and found the ground reference was in the Delphi DC/DC converter connection.  When I removed the high voltage cable the voltage reference to car ground went away.  So either the DC/DC converter is the issue or the cable is.  It might explain how the pack could be fully discharged in such a short time.  Using a 33k ohm resistor I measured the leakage to car ground from the high voltage point of the battery pack.  I got a 2.5V drop on the resistor indicating a 0.076mA current flow.  That is well inside the spec for the Delphi DC/DC converter. The voltage that appears to car ground is disconcerting and is probably what gave me a shock.   But that small amount of current leakage should not have discharged the pack in just a couple of months.  Something else must be going on.  The BMS was the only other component that was connected. I still need to connect that and measure any current leakage.  When I first started testing the BMS I found that the 3.3V DC/DC converter on the board was not working.  That explains why the BMS was not sending any CAN messages when the USB was disconnected.  I need to repair that board so I can do some more testing.

Other fun I have been having before the first drive is installing the carpeting and front seats.  The carpeting I got from a company called Stock Interiors. When I received it I checked it against the old carpeting.  It seemed to have the right shape and contours in the right place.  Aftermarket new carpets never have any of the holes cut so I had to cut the holes for the gear shift, e-brake, throttle pedal and the seat mounting points.  I did not realize at the time that the contours for the seats areas were not quite right.  I struggled to get the carpet in the correct position before I started cutting.  It seemed like the carpet was too small in some areas and too big in others. The carpet over the transmission tunnel is loose, but under the seats it is tight. The info on the company's website says it should take 3 hours to install the carpet.  I don't know what universe that got that number from but it took me two days to install most of it.  I still don't have the kick panels or the rear seat section installed.  That number is probably for a late model car that does not have as many contours as the 320i.  I got the driver's seat installed, the steering wheel and center console.  Everything I need to make the first test drive.

A video of all this fun is avialable here.

Details

Published: 10 May 2016

Wheels-a-spinning II

Hard to believe that it has been almost exactly 2 years since the wheels spun under electric drive. In my blog and video of May 2014 I described and showed how I connected the Siemens and DMOC to the car and had strapped up all the batteries in the wooden crates they were received in.  Using a bench-top contactor system, a throttle body and a GEVCU I was able with the to get the wheels spinning,  just to prove all the hardware worked.  Now 2 years later I finally have all the components assembled in the car and all of the assembly has been completed in the engine compartment.  I got the DMOC bolted in and connected to the buss bar and Siemens.  I installed the GEVCU on top of the DMOC.  In my last video I had made a measurement to test that the GEVCU would fit there.  It really was the best place to mount it considering all the wiring connections.  All those connections are now complete.  I also came up with a mount for the throttle body.  Using some angle aluminum pieces I fabricated a mount that would bolt to the side of the DMOC, using the screws that hold the DMOC cover as fastening points. I also came up with a fixture to hold the throttle cable.  That throttle body from NetGain is real piece of bling. Very nicely anodized and is a dual Hall effect sensor. The only issue I have with the wiring is with the  fabricated wiring harness I got for the GEVCU from EVTV.  It is very nicely made, all the wires are color coded and labeled.  The issue is that I only need about 2/3 of the wires in my build.  There are 35 wires on that harness so I have about 20 wires that have no place to go.  I might just coil them up and put them in an enclosure so I could use them in the future if I need any of the unused signals.
I finally got all the wiring and battery connections done so that I could start charging the full battery pack.  Of course that did not go as planned.  When I installed the new Siemens EVSE and turned it on for the first time it came up in failure mode.  I called Siemens and they had me try all kinds of resets but nothing worked.  So they are going to replace the unit.  I did not really need the unit to charge the car.  I really wanted it so I could test out the J1772 interface to the Brusa to make sure that would work with public charging.  To charge the battery pack what I did was removed the J1772 cable and plug from my old EVSE and put a plug on the other end so it could plug into the 240V outlet I had installed for the Siemens.  The Brusa charger did not start at first.  I found through the monitor program for the Brusa that I had forgot to connect a thermisitor for the battery temperature measurement.  Once I added that the Bursa started right up and I was able to set the parameters in the ChargeStar program.  The batteries only had about 7 AH of energy so for the pack that corresponds to about 2.5KW.  The pack is 25KW so at 3.3KW charge rate per hour that means it will take just over 6 hours to charge the pack.
Before fully charging the pack I wanted to make sure all the subsystems worked, from the DC/DC converter, DMOC, Siemens, GEVCU, BMS and instrument cluster and LEVID driver.  When I first connected the high voltage through the contactor box that was controlled by the GEVCU the DC/DC converter did not initialize.  The Delphi requires a CAN message to be sent with the target charge voltage before the unit will output any current.  I thought that was in the GEVCU code, but apparently it is not.  To get the DC/DC converter running I programmed another GEVCU board with the Delphi program.  That worked to get the Delphi running and charging the 12V battery.  The next test was to spin the Siemens motor. That would test the motor, DMOC, high voltage wiring and GEVCU.  I calibrated the throttle and connected the gas pedal to the throttle cable.  Pressing down on the pedal I expected to hear the nice sweet sound of the Siemens spinning up.  Unfortunately all I heard was a rough sound and felt a lot of vibration.  Even with full throttle the DMOC only drew 10 Amps.  At that torque request it should have put out 100 or more amps.   Something was definitely wrong.  I brought up the embedded website on the GEVCU. The overview page showed all green indicators.  Next I brought up the dashboard page.  When I pressed the throttle, the throttle indicator ramped, the requested torque gauge ramped but the tachometer showed no rotation, even though the motor was making sounds.  I next brought up the ccShell program that is used to program the DMOC.  It has a viewer screen on which any parameter of the DMOC can be displayed.  The one of interest was the IR2Hertz parameter, which is the motor RPM value. When I pressed on the throttle pedal the IR2Hertz value jumped around, first showing 22 rpm and then -24 rpm.  To further check the system I mounted a tire on one of the rear wheels.  Just powering the DMOC with 12V I brought up the ccShell program and watched the IR2Hertz value as I manually rotated the wheel.  The IR2Hertz value showed the same wrong values from before. Unfortunately this is an indication the motor encoder signal is corrupted in some way or the DMOC has failed.  I can't believe the DMOC could have failed, it has only be used a half dozen times and not really for very long or for high power output.  The encoder hardware in the Siemens motor is most likely not bad either.  Both the motor and DMOC have been tested together several time, the last time just a few months ago to test the GEVCU in the CINCH enclosure with the new wiring harness.  Everything worked well then.  The only thing linking them is the encoder cable.  I removed the cable to test the continuity, but first I examined the connector shells and jacks on the cable and the DMOC and Siemens. What I found was on the Siemens jack one of the pins was bent over and pushed in.   It turns out the bent pin is one of the encoder pins.  I had to remove the connector jack from the Siemens to access the pin to push in back in and straighten enough so it would go into the connector.  I was able to straighten the pin enough for the cable connector to go on.  After remounting the connector jack and connecting the cable I tested the RPM reading by manually rotating the rear wheel again.  Now I get a good reading of RPM.  The bent pin was causing one of the encoder signals to be lost.  Once I put the DMOC back together and got all the other connections reinstalled I started up the system and connected the high voltage.  Finally a nice smooth spinning of the Siemens!  I put the transmission in gear and spun the rear wheels!  Now all that's left is to assemble the dashboard and install the new carpeting and seats and it will be ready for a test drive.

A video of all this fun can be found here.

Details

Published: 28 March 2016

Still Not Rolling Yet

You would think over the last four months I would have gotten enough things done to get at least the wheels spinning.  Well the car and electronics are not quite there.  I was able to get the Siemens motor mounted back in the engine bay and connected to the transmission. But that, just as everything else took way longer to complete.  The main problem was that the BMW motor mounts that I planned to use did not work once the motor weight was loaded on them.  They did not work because of the design of the main bracket for the Siemens.  Because the Siemens motor mounts are on the front of the motor the mounting bracket essentially cantilevered off of the motor mount points in the engine bay.  The problem with the BMW motor mounts  is that they are designed for compressive loads, not tensile loads.  When I put the weight of the Siemens on the bracket, the rubber in the BMW mounts stretched and the motor dipped down 2 inches so that the motor was resting on the cross member.  I had to design new hard mounts out of aluminum block.  That took several weeks to get machined, but worked out very well.
I also got all the water cooling lines connected and leak checked.  I connected the Siemens to the Delphi DC/DC converter as one cooling loop.  The DMOC will have its own cooling loop because the inverter is much more susceptible to heat than the motor or the Delphi.  I did have a problem with the water pumps though.  The way I had the pumps mounted the impeller was on the bottom, facing down.  When the pumps were first tested and did not work well is when I discovered that they can be mounted in any orientation, except with the impeller down.  So I had the disconnect the pumps and flip them 180 degrees and remount to the frame of the car.  I guess one of the pumps did not like being inverted and would not pump after remounting in the correct position.  I had to buy another Laing DC5 pump to replace that pump - a costly mistake.
The GEVCU I modified to drive my instrument cluster, which I call LEVID was tested and worked very well. LEVID stands for Legacy Electric Vehicle Instrument Driver.  I modified a GEVCU so I could mount a daughter board that had isolation for serial and I2C communication.  The serial interface is used to drive the 4-digit 7-segment display that is mounted in the middle of the tachometer on my instrument cluster.  That display will be used to show a digital value of the numbers being set on the analog gauges that is selectable.  The I2C interface is for a Real Time Clock (RTC) that is read and used as to display the time as another message on the 7-segment display.  I programmed a 2nd GEVCU with a program that simulates the CAN messages that the DMOC and BMS will send during the operation of the vehicle and tested the LEVID driving the gauges.  I had to build a wiring harness to connect the LEVID to the instrument cluster. Everything looked really good.  Next step is to mount the LEVID in an enclosure and put the instrument cluster back in the dash.  Speaking of which the dashboard is in bad shape.  When I first got the car there was a straightened paper clip stuck in the side of the hazard warning switch.  When I pulled the wire out the hazard flashers turned on.  When I pressed the button it did not stay in and the flashers continued to flash.  The wire was there to keep the switch in the off position.  Unfortunately to replace it required taking the whole dashboard apart which I did.  I also had to drill a 1" hole in the dash to mount the emergency off switch for the electrical drive system.  The dashboard along with the instrument cluster still have to be installed.
 One of the issues I have is where the 320i is located in the garage with respect to where my EVSE (charging station) is located.  I had originally mounted the EVSE near the door leading to the garage as that was the shortest run for a cable conduit to the breaker panel and the Leaf I was leasing had the J1772 charge port on the front of the car.  The problem is with location of the 320i. The charge port for the 320i is diagonally across the garage from the EVSE.   That distance is longer than the cord on the EVSE, so I decided to make a new conduit run to the opposite corner of the garage.  Forty feet of conduit and 50 feet of wire was tough to pull.  I plan to get a new EVSE, a unit from Siemens that EV West sells (click here).  That will be an upgrade over the EVSE that I have now and will also be able to do 7.6KW charging (but not on this build, at least not now, the 320i has a 3.3KW charger).  The Siemens can be set for any charge level and it has a timer for delaying the charging
I got the front battery box installed, the batteries installed and all of the battery cables connected.  All but one.  When I changed the location of the maintenance switch to be on top of the plexiglass isolation, I had to make a new cable run that would go from the switch to the contactor box.  I thought I had measured that correctly but when I went to connect the cable  connector to the stud on the maintenance switch the cable was too short - about 1" short.  This was the last connection to complete the battery circuit and is required to be able to charge the pack.  The two options I have is to make a new cable or make a standoff.  Both will take about the same amount of time because I do not have any cable connectors or heat shrink so I would have to order those supplies.  Having the standoff machined will take at least a week, but I would not have to take the contactor box apart, which is my preference.  Once I get that standoff machined and installed I should be able to charge the battery pack and then get the wheels spinning.
A video of all this fun can be found here.