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Published: 21 November 2015

Last bit of Wiring

I thought I would have everything done now to get the car rolling but things just keep popping up and taking way longer to finish.  The 12V wiring is a good example of that.  I previously showed that I had to install a new fuse box with 12 circuits in it.  That was to accommodate all the pumps, fans and EV electronics.  The fun started when I tried to connect all the circuits.  The only way I could see to make all the connections was to get another contactor box and use it as a wiring cross-over box.  Of course that meant having a way to bring wires into and out of the box.  The Ampseal connectors are the easiest to use and they come in all number of pin counts.  Since the main contactor box had a 14-pin Ampseal I decided to use that size for the wiring cross-over box.  I purchased a box that would fit in the engine compartment where I had room, but unfortunately the sides of the box were not wide enough to accommodate the size of the Ampseal feed through.  I had to get a larger box, which actually made the wiring inside easier but it caused another problem in the engine compartment.   The place I had available for the cross-over box was right near the main disconnect switch.  In my last video I showed that switch being mounted on the side of the plexiglass isolation box I used for the buss bars.  With the new larger box for the wiring connections that switch did not fit in that area anymore.  I really did not like the switch on the side because it was going to be difficult to get to. It also caused the battery cable to make a wide loop.  I really wanted to put the switch right on top, but with the position of the plexiglass enclosure the maintenance switch would interfere with the hood.  That interference was only do to the arbitrary position I mounted the buss bars in.  If the buss bars were moved down 1 inch then the maintenance switch could be mounted on top and clear the hood.  So that is what I did, I moved the buss bars, but unfortunately that meant getting a new plexiglass enclosure machined, which is on order now.

One of the issues I have had with the GEVCU is that the enclosures, even the CINCH are not 100% moisture free.   The residual solder flux on the pcb will corrode if exposed to moisture.  The lead based solder will also corrode and so will any of the non-gold connectors. The corrosion could lead to reliability issues with the control electronics.  In OEM manufacturing the way they get around this problem is to conformal coat all electronics.  Conformal coating is designed to seal the electronics from the environment.  There are lots of conformal coats available and I got one in a spray can from my local electronics dealer.  It is silicon based and makes a very tough and durable coating when fully cured.  The conformal coating material I got also can be removed with a solvent, so if the board ever needs repair the coating can be removed.  It also has the feature that it fluoresces under UV light so it is possible to check the coating coverage.  The spray coating was very easy to apply, one coating dries to the touch in 5 to 7 minutes.  I applied three coats of both sides of the board.  Besides the GEVCU I also conformal coated the BMS board.  I covered all areas with tape that did not need the coating, specifically the CINCH enclosure gasket and the connector for the WiFi antenna on the ConnectOne WiFi module.  The one issue with the silicon conformal coat is that it takes 48hrs to cure at room temperature.  I bought an oven so the next time I do conformal coating I can cure the coating faster (2hrs at 150C).  The other issue with the coating was related to the WiFi.  I was planning to use a patch antenna, because the CINCH enclosure does not have a feed through for an antenna and the Wifi signal would pass though the plastic enclosure .  Patch antennas require a ground plane to work well.  When I initially tested the antenna it worked very well because the top metallization on the GEVCU board was providing the ground plane.  What I found after the conformal coating is that the patch antennas do not work anymore!  I think that the fairly thick (~0.5mm) of dielectric is preventing the patch antenna from working.  I realized that I could drill a hole in the CINCH faceplate that held the Ampseal 35pin connector.  There was just enough room to drill a hole and mount a SMA feed through.  I could now mount a dipole antenna on the outside of the CINCH enclosure so the WiFi connection would work.  I probably will remove the antenna when not using the WiFi.
Lastly I got a new vacuum pump for the power assist brakes.  The first pump I tried to use had a lot of extra wiring - wires for the pressure switch, a relay and wires for the pump itself. I was already struggling with placing all the wires so I was looking for an alternative. I found looking on the EVWest website that they had a vacuum made by CVG that has the pressure switch and relay integrated into the pump, so the only wires that need connecting are just the power wire and ground to the pump.  The CVG pump was considerably larger than the other pump so it required an new bracket to be machined and painted.  I thought I had everything covered now with vacuum pumping but I discovered when connecting the vacuum lines that the connector on the BMW power assist used 12mm hose and I was using 3/8 for all the connections.  That meant getting another hose adapter to accommodate that hose size.

A video of all this fun can be found here.

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Published: 18 September 2015

Almost Rolling

This summer there have been a lot of distractions from working on the car although I have been working on the car when I am not doing anything else. And I have been taking a day off of work here and there to work on the car. What I struggled with was finishing the brake job. In the last blog I talked about the upgrade of the braking system. That upgrade took longer than it should because of various problems. What really stalled me was installing the brake pressure transducer. I had a really hard time coming up with the fittings to adapt the brake pressure transducer to the brake system. The pressure transducer is used the tell the GEVCU to apply regen torque when the brakes are engaged. The problem I ran into is that BMW uses a very special flare on the end of the brake tubing. It is called a bubble flare or convex flare. Although many places make adapter fittings I could not find exactly what I needed.   The main problem is the brake transducer came with 1/8" NPT and it has to be mounted on in a tee in the brake line. That meant I had to adapt 1/8"NPT to convex flare. I could not find fittings of the proper sex for the setup I was trying to use. After several tries I finally got all the correct fittings. I had to use a custom made stainless steel braided brake line to accommodate the placement of the transducer and to adapt it to the braking system. Related to the braking system is the clutch slave cylinder. I found I had to replace the slave cylinder and that turned into another big job. The slave cylinder cannot be bled while mounted on the transmission. BMW put the bleed screw on the bottom of the cylinder so the slave cylinder had to be removed and held in a special fixture to be bled. That had to be done first before bleeding the main braking system. I used a pressure bleeder to finish the job.

On the Electrical Vehicle front I now have nearly all the high voltage and low voltage wiring done. The high voltage wiring required the completion of the secondary contactor box that controls high voltage to the PTC heater in the car and the box heaters in the battery boxes. I still have figure out what to do with the thermistor wires coming from the battery box heaters. I don't need precise heating control and the heaters are somewhat self limiting in the amount of heat given off. I also have temperature monitoring in each battery pack via the BMS. The temperature measurement is really only required to determine if the batteries are too cold to charge. That normally will not be an issue for me because my habit with the Leaf is to put it on the charger as soon as I get home. If the batteries were cold from the car sitting in the parking lot all day they will warm up by the time I drive home. But it was a lot easier to add the heaters in the boxes before the batteries were installed, just in case I need to heat the batteries

I also got all the wiring connections completed for the BMS and made up the harness connector for the Cinch enclosure. I really like the Cinch enclosure because of the design and the very strong sealing mechanism. But the harness connectors are harder to assemble than Ampseal. I did not think that was possible. It took me several tries to get all 18 wires inserted into the harness header. Those connectors are supposed to be able to use with 26GA wire. I have 22GA and I really struggled getting those wires in the harness header. That size wire is used for the BMS as a safety feature (no fuses required, if a short occurs the wire will just melt and open the short). I did finally get a completed header assembly and was able to test the BMS. All temperatures and voltages were reading correctly although VBAT2 for the second battery segment had to be negated to read correctly. That means for the ADC the voltage was inverted. I reviewed the layout of the BMS and found there was an issue with the VBAT2 measurement circuit. I came up with a rework on the board that was fairly simple and it worked to fix the measurement problem. I had Collin Kidder send me his board to apply the same rework.

The last major bit of low voltage wiring needed is connecting the GEVCU to the car. I originally thought I would do that connection after I got the engine and DMOC back in the car because I plan to mount the GEVCU to the side of the DMOC. Having the engine out of the engine bay has worked really well to do the wiring because I can climb into the engine bay to work.

Hopefully in the next blog I post I can announce driving the car under electric power. The last time it was on the street as an ICE mobile was November 2013. If I get it rolling soon this conversion will be completed before two years are up.

A video of all this work can be seen here.

Details

Published: 01 June 2015

Getting Closer

I have been spending the last six weeks working on all kinds of small issues.  I needed to make the mounting hardware for all the peripheral components.  This includes the radiator/fan cooling unit, the water reservoirs, the water pumps, the vacuum pump and vacuum reservoir and the DC/DC converter.  The mounting hardware takes a lot of time because it has to first be designed, then machined and then painted. I also made some mounting hardware to mount the Brusa charger in the spare tire wheel well in the trunk.  The Delphi DC/DC converter proved to be a problem mounting because of the cooling lines.  The converter has 3/4" connections that required a hose that was more than an inch in diameter to be uses.  A hose that big does not bend with a tight radius so I had to adjust the position of the converter to account for that stiff hose. I also had to get some adapters to go from 3/4" hose to AN8.  In addition to the mounting hardware I also have been working on wiring all the pumps and cooling fan.  These all go through a new fuse box that I setup that will run off the DC/DC converter. Other mechanical issues I have been working on are the brakes. The front brakes got new rotors, calipers and pads and I purchased a upgrade kit for the rear brakes to convert them from drum to disk.  The installation of that kit went very well, although removing the left rear wheel hub was quite challenging and required a 5-ton hydraulic puller to break it loose.  It probably has never been removed in the car's lifetime.  The upgrade kit included some very well written instructions and all the hardware necessary for the conversion, including new hubs, new rotors, new calipers and new brake pads. A link to the brake kit vendor is here (Aardvark Racing). Other work on the brakes included restoring the vacuum booster unit and master cylinder.  The vacuum booster was in very bad shape - rusted and paint peeling.  So I removed it, wire brushed all the old paint and rust and repainted it.  I also rebuilt the master cylinder.  I am still amazed that I can get brand new parts (albeit 30 years old) from the BMW dealer.  The master cylinder repair kit , the seals and bolts and a new brake fluid reservoir were all available.  Some of the parts came from Germany.

On the electric vehicle front I started placing batteries in the battery boxes.  I started with the trunk box first.  This box is mounted on some sliding rails that allow the box to be slid forward for loading and testing batteries and then slid back and locked in place during vehicle operation.  The box design was detailed in a blog and video eariler this year (see below: BMS Respin and Battery Box Mounting). The batteries in that box weigh 254 lbs and I wanted to make sure the rail system worked.  I coated the rails with a dry fluro lubricant to help with the sliding.  The system worked just as planned and all the batteries were loaded without any issue.  Next step is to strap them all together and connect the battery cables.  I finished the work on rear seat battery boxes which included sealing and securely attaching the boxes to the seat deck.  Batteries were loaded in those boxes, but not strapped up.   I also started to work on the wiring for the BMS and battery heaters.  Next step will be to strap up all the batteries and finish the peripheral wiring.
Speaking of the BMS I also have been working another version of the BMS board.  The new version has a circuit designed to measure the battery current with an external shunt.  The board works exactly the same as the earlier version with only difference being the pinout on the connector.  To accommodate the shunt connections I had to make one common connection for the thermistor reference line.  All the thermistors are referenced to a current-limited +5VDC.  The two designs of the BMS boards give people an option to either use the CAB300 flux gate sensor or a current shunt.  The flux gate sensor has the advantage of no break in the battery cable. The current shunt has the advantage of higher accuracy.
A video of all this work can be seen here.

Details

Published: 10 April 2015

Formula E Race and EV West Visit

Last week I was fortunate enough to be able to travel out to California to see the Formula E race in Long Beach CA.  This is something I have been wanting to do since the race series was announced last year.  There were only two US dates, three weeks ago in Miami and last week in Long Beach.  I knew the California race would be better because Long Beach is not far from San Marcos, where EV West is located.  They hosted the race and had a get together before and after the race.  I was able to shoot some video of race, a link to the video is below.  The quality of the video is not that great.  It was brilliantly sunny that day which was great for the race but made it very hard to see the LCD viewfinder on the camcorder.  They also had a lot of barricades setup so it made it hard to get close to the race track.  They have to do that because when the cars crash all kinds of parts come off the cars, some at velocities that are lethal.  But the most notable feature of my video is how loud the cars are when racing.  You don't get that sound on the produced video of the race that is on YouTube (Link here).  The electric motors and gears really scream when they go by at 100MPH.  And you can really hear the tires on the pavement too.  The race had a really great turnout, probably well over 20,000 people.  The admission was free, but it was Easter weekend.  It was a really great time and I look forward to next year's race.
While I was out there I spent some time at EV West.  For the past six months they have been involved with a Smart Car repurposing program.  The Smart Car are fleet cars that have been salvaged.  Instead of crushing the cars and recycling the metal EV West is removing all the usable parts and making them available for sale.  Most notably are the battery packs, which are a Tesla design using the 18650 cells.  They cannot sell the whole battery pack, but they can sell the battery modules inside.  Each pack holds 8 modules that are 3KW/hr each.  It is quite amazing how small 24Kw/hr is with the 18650 cells.  I could almost put 48KW of these batteries in my 320i and probably take up less room and weigh less.  Maybe something to consider for my next build.  All the other parts of the drivetrain are available as well as all things like brakes and wheels.  While I was there I also looked at a Scott Inverter.  This is a 150KW inverter that might be a possible upgrade for the DMOC later this year.  The Scott has a very extensive software control package with a lot of functionality.  The only feature I did not see was the ability to program the amount of regen in the gas pedal position.  That is something that can be done on the GEVCU and gives the ability to drive with one foot.  The BMW i3 that I drove last year had that feature and I really like it.
In this past week I was also able to test the Delphi DC/DC converter that I replaced the HV input connector that I reviewed in the last blog and video.  The Delphi is unusual in that it requires 12V on the output connector to enable the converter to startup.  According to the user manual the Delphi requires that 12V to power up the internal circuitry and once the converter starts then the internal circuitry is powered by the HV.  The converter also seems to need a CAN message to set the output voltage to 13.5V.  This is very strange but it can be accommodated by the GEVCU.  I initially had a problem with the CAN messaging because unknown to me the CAN transceiver on the GEVCU I was using was not working.  Once I switched the CAN channel the converter started working and output current at 13.5V.

A video of the race and EV West visit can be found here.