Driving and adjusting

Can't believe it has been 6 months since I posted any progress.  The car is all back together and and has been my daily driver since early March.

Since the Audi has been functioning as a car I have been doing mostly cosmetic stuff and non-EV maintenance tasks.  After I got the car moving there was a shuttering when I would accelerator, it was the same as it did with the ICE engine.  When the ICE engine was installed, I assumed it was a cylinder missing because it would smooth out when I let off the gas.  Same feel with the electric motor was installed?  Well now I know what a CV joint going bad feels like.  Without the ICE motor it only took a couple hours to replace the 1/2 shaft with a new performance unit from Raxels.

After driving around with aluminum battery boxes for a few months, it was time to upholster them so they don't standout as much. I used some 3/8" fiber board covered with carpet backing foam and upholstery fabric over it.  The panels are attached with some velcro so they can be easily removed for any battery maintenance.  The biggest benefit of having these installed is the reduction of the road noise that can be heard.  Also it looks more like completed car rather than a project.

One of the most annoying parts if driving the Audi has been the oil warning built into the gauge cluster.  Not only would this oil can flash up on the dash, there was a loud annoying tone to go along with it.

 The Audi has an oil pressure switch that closes contacts when there is 10 psi of oil pressure, easy enough to just ground the wire so it always thinks it has oil pressure.  The problem is when RPM is 0 it expects the pressure switch to be open, if it is closed it gives the same warning every time the motor stops turning.  The beeping at every stop sign got old very fast.  The first attempt fix this was using a few components and a transistor to pull the oil pressure low whenever a tach pulse was received.

This worked OK after some tweaking of the pots to get the timing dialed in.  For most driving this worked fine but I could never workout the settings for when the car would just creep slowly.  There was a hysteresis required that this simple circuit just could not provide.  Probably could have done something with discrete logic but I have been looking for an excuse to do an Aduino project and do a little programming.  I have not done programming since I took FORTRAN in collage so a small project is what I needed.

I ordered a Arduino Nano and put together a breadboard of what I though would work for hardware I wrote a couple simple sketches (that's what they call an Arduino program) to test the input from the tach and the output for the oil pressure.  The advantage of being software based I could test each separably before I tried to get the logic between them working. This is my breadboard configuration.

From the breadboard I soldered the parts on a circuit card and mounted it in little box with a D-Sub connector.  I wanted to box to be easily to remove for programming when needed.

The sketch I wrote uses a hardware interrupt the built in timer and one output pin.  The Arduino has way more capability and lots more input and output pins but they were not needed.  I'm sure a real software engineer could do much more efficient code but it works.

For now I'm driving gas free, I will try to get another post up soon with some energy usage.

Driving, problems and rework

Been a while since I have updated, but I have has the car moving under it's own power.  Sorry I don't have any video will try to get some soon.  Here is a picture of the first drive without the front body plastic installed.

The end of November I went for my first drive around the block and up and down the street a few times.  The first problem I had was the DC-DC controller fuse blew, draining my 12 volt battery, shutting down the controller leaving the car dead in front of the house with all the neighbors watching.  Shutting everything down allowed the battery to recover enough to get back in to the garage.  Looking on line I found this was a common problem and is either caused by the capacitors in the DC-DC converter trying to drive the car when the main pack sags or by an AC ripple on the DC high voltage caused by the controller.  I installed a diode to prevent the capacitors from back feeding and a 100 uH inductor to kill any ripple.  I also changed from a 10 amp fuse to a 15 amp fuse. With about 50 miles on the car since I have not had any more problems.

The next problem I ran into was not having enough heat.  At 20 degrees the amount of heat  was enough to keep the windows from fogging and make it tolerable to drive.  The problem was there was not enough heat to melt frost off the outside of the windows.  This is kind of important in the winter in Iowa.  So I decided to re-do the heater.  I decided to use a couple 1500 watt PTC heater elements that I removed from heater I found at Home Depot for $20 a piece.

The problem is getting to the heater core.  The entire dash has to come out of the car along with the structural cross bar.  Working in the unheated garage, with one of the heater running inside the car, it took me a day and a half just to get to the heater core.   The heater core slides down into the black square in the center of the photo below.

Once I got the heater core out it was time to modify it to hold the PTC elements.  Taking a grinder and pliers to the heater core made room.  I stacked the two elements and held them in place with some fire block expanding foam.  Then sealed up the rest of the fins and small holes with some high temp RTV.  The final heater core ready to be re-installed is below, with the scraps of aluminum that were removed from the heater core in the back ground.

I have the heater core back in and wired but I had to order a new switch that will be installed in the dash to control the heaters.  I will have a low and high settings for 1500 and 3000 watts.  So the dash panel will stay out until I get the new switch.

After hearing more about bad things that can happen to Li-Po4 cells when they are charger below freezing, I decided to add some battery box heaters.  I found some flexible silicone rubber heaters on line at Omega.

I have these hooked up to 120 volt AC plug to connect when I pull in the garage   Even at 2 watts per square inch I found they get very hot.  To disperse the heat I attached these to a piece of 0.063 aluminum under each battery pack between the insulation and the battery and connected them through a cycling relay that turns them on for a minute and off for a minute.  From 20 degrees they get the batteries up to about 45 degrees in about 3 hours.

I also did a little body work on the car.  Like most ICE cars, there was a cutout in the back for that tail pipe.  Since I don't have a tail pipe it looked silly to have a cutout.  I used some fiberglass cloth and resin to fill the hole and covered the panel with some foe carbon fiber.  I think it make it look much better and I'm sure will cut 2 seconds off my 0 to 60 time.