Tuesday, September 13, 2011

On the Road Again

All Willie Nelson references aside, the Z3 is back on the road.  There's a lot to tell, and I'm sorry I haven't posted more as I was working, but as most of you know, I have a deadline that I had to make.  This made for some very long days and nights in the garage.  I'll touch on some of the highlights, good and bad.

The controller for the MasterFlux compressor comes as a circuit board with an aluminum heat sink anchored to one side and all the components open to the world on the other side.  You don't have to be a computer expert to know that probably ought to be protected from the elements.  I started looking for a project box big enough to put it in and would fit in the space I had picked out for it, but found none.  It wasn't long before I realized I was going to have to build my own.  Well, I figured that would be fun.  My material of choice would be thin sheets of aluminum, but I don't have a press break, or access to one.  There was no way I was going to be able to build a nice box out of metal with neat edges.

OK, that meant plastic was the material of choice.  I found someone on eBay selling sheets of PVC plastic, so I ordered a 2'x4' sheet.  I was able to cut it quite easily with a utility knife and a metal straight edge.  It was clearly formed with a PVC foam-like material rather than the type used to cast PVC joints for plumbing.  But on thing was certain, it would glue the same.  I very carefully cut sheets the proper size, planning on two sheets per side, sandwiched together, with staggered edges so I would have more surface area to make sturdier lap joints at the corners.

My plan to build a box around the controller was going well.  But then my dad had a great suggestion.  He noticed that the heat sink is a bit larger with the edges sticking out beyond the edges of the circuit board, so he suggested making that one side of the box and simply enclose the circuit board.  Brilliant!  I was able to do just that and build a secure mounting system and put it exactly where I had hoped I would be able to.  This had the added benefit of leaving the heat sink open to the outside air for cooling

Notice the fins of the heat sink facing the front of the car between the two battery packs.  Right next to that, to the left, is a little project box that holds a large diode and two relays.  The diode is to prevent current from the capacitors on the controller board from flowing back into the car's traction system should the voltage in traction system drop below the voltage stored in those capacitors.  Apparently this was a common problem with the MasterFlux units that they've decided to overcome by recommending you buy an extra $25 part.  The relays work like this: the on/off switch on the car's dashboard for the A/C system triggers one relay, which provides power to the fan mounted on the condenser at the front of the car, and to the second relay.  That second relay simply makes a contact that will allow the 5V signal back to the controller turning it on.

(By the way, notice the nice new braided connectors between the batteries.  Nice huh? )

All of this should work flawlessly.  In theory.  You see, I tested what I could before hooking everything up, but there was no way to test all of it as one system after it was hooked up, until all the batteries were in.  Plus, I have no idea if it's even safe to run the compressor before the system has been evacuated of air and charged.  In fact, I've been trying to reach Revolt Electric (the resellers of MasterFlux products) to ask them about this and a few other things but they have been, how shall I say, less than diligent about returning emails or phone calls.  Part of being a reseller is living up to the responsibility of offering end user support, and they're falling short at the moment.

Tomorrow morning, I'm taking the car into a local BMW shop to have them evacuate the system and charge it.  First, they'll put a vacuum on the hoses and pump all the air out.  They'll leave it like that for a couple hours to be sure it holds the vacuum.  If it does it's good to charge.  At this point I have no idea if it will.  I can't express how much I hope it does, but there's no telling.  Since one of the new joints in the system had a brazed fitting, I think that one will be fine.  The other one was still an accursed compression fitting.  I give it a 50% chance of holding a vacuum.

If it holds up they'll charge it and I get to turn it on for the first time.  I'm not worried about incorrect wiring and/or damage to the system, but there is the distinct possibility that it simply won't work for some reason which I can't conceive of at the moment.  I'm about 90% sure that will go well.   Whether I drive out of the shop with A/C tomorrow, only time will tell.

They are also going to align the front end to take out all the toe-in.  I never had it re-aligned, so it will be interesting to see how much of an impact this has on energy consumption.  Sadly I won't know right away because the new meter I put in isn't working.

Actually, the meter is not the problem, it's the original pre-scalar I was using with the Link-10 meter.  When I put power to the system yesterday, I turned on the meter and started running through the various menu setting to set it up for the car.  When it was done, it read that the system voltage was 68.8V.  Wha...  I double checked that I'd selected the 1/10 pre-scalar knowing full well that I'd never seen a 1/4.3 setting that would be necessary to see 68.8 Volts.  Eventually I pulled the meter out of the console and actually measured the voltage on the wires coming from the pre-scalar.  I found that it read 6.88 volts.  Well how about that.  Apparently while the car sat doing nothing over the past 4 months, the pre-scalar developed some sort of problem that renders it useless.  I have no idea how, or why, but a replacement unit is $54.  *Sigh*  A new one is on the way. 

Astute readers will have noticed in the picture of the motor bay that the big red slap switch I had in the prior builds is gone.  "Where did it go" you ask?  Well after I pulled it out to start the work in the area, I noticed something peculiar about one of the contacts on the positive terminal side.  Take a look:

You can see in the top right side what the contact pads should look like.  They are little silver pads soldered on the copper bar.  However in the bottom frames, you can see that one of them has completely melted away.  The bottom left picture is the bottom bar in the contact, and the bottom right picture is it's mate above.  At some point, there was some serious arcing in there that, for all intents and purposes, destroyed this switch.  Well there was no way I was going to put it back like that, and I see no reason in replacing it with a like one as there will now be the possibility of sending even more current through it.  Nope, I need to find some other safety disconnect.  But, that will have to wait for later. 

I finally added an expansion tank for the coolant used to keep the Zilla cool.  Finding a location for it was a challenge. The fact is, it's on the opposite side of the car from where the pump is.  As a result, there are coolant hoses running all over the place.  The underside of the car is, quite frankly, a bit embarrassing now.  It's just too crowded with stuff and it all looks a bit thrown together.  Such is life.  The cooling system does seem to work great though.

Yesterday after putting everything back in and together, I was working near one of the batteries while touching the chassis of the car, and I grazed a battery and felt an unmistakable shock.  What the!  My mind raced.  I got out my meter to check and sure enough, there was continuity between the chassis and the battery pack.  I stood there cursing, wondering how the hell that had happened.  I disconnected the positive most terminal and started looking to see what had happened.  Eventually I isolated the problem to the motor.  My first though was that as I'd lowered the battery pack on top of the motor, I must have crushed one of the lugs and it shorted out to the motor's housing.

There was no way around it, that pack was going to have to come out.  Mind you, this is coming less than an hour after I'd put the final bolt in holding everything together.  What a bitter pill that was.  Rather than take the pack out as a whole, I decided the best thing would be to dis-assemble the first row of batteries and remove them so that I could see the terminals which are under them and if I'd crushed a lug.

What I found was no crushed lugs, but one was clearly wedged in there and under pressure.  I as able to get to it and get it out.  I found that the plastic boot on the terminal had what amounts to a pressure wound on top of it and was actually pierced, ever so slightly.  The heat shrink tube underneath it looked intact, but I cut if off and could clearly see a hole you could fit a pencil lead through when I held it up to the light.  There it was, that was what had been touching the chassis.  I found a less risky path for that wire and bolted all the wires back in place.  I checked and there was no continuity.  Problem fixed.  Whew!

This morning, I re-assembled the rest of the system, put power to the system, dropped the car to the ground and carefully drove out of the garage.  I took off down the road cautiously and found that the car was driving perfectly.  Furthermore, the wobble that was in the drive line before it went up on blocks was now completely gone.  The Warp 11 motor was perfect again.  Finally, on the road again.

Tomorrow is my appointment with the shop, which I'll report on.  The rest of the week will be spent replacing that pre-scalar, and getting ready to trailer the car and tow it to Missouri for EVCCON.  I am genuinely looking forward to that. 


Gam0ra said...

You know...going through Denver only adds 200 miles to your drive and provide you with a convenient and free place to stay the night.

It's amazing the amount of work you put into that car and all the excellent maker-style work your figuring out how to do.

Anonymous said...

Hi Tim.
Great to hear the Z3 is rolling again. You picked the same spot for the coolant reservoir as I did !

For the safety switch, why not look into relays? I am using two/three EV200's to disconnect the battery packs from eachother. The emer-switch cuts the 12V going into the aux & contactor box.


Tim Catellier said...

200 miles for a night's lodging isn't a bad deal, but having to pull the car through the Rockies in order to head East out of Denver is a bit more than I'm willing to do I'm afraid.

The car has definitely been a labor of love. But I think it's been worth it.


I hadn't considered using contactors to disconnect the pack but I'm going to think on that idea. What I had in mind was more of a physical switch, actuated by hand, rather than a separate system relaying on electricity.

Jack Rickard has been using a large switch that has two copper plates that slide next to each other to produce a connection. On video it looks bigger than I might like, but it has plenty of surface area on the connecting plates to prevent arcing or heat build up. I'll keep everyone posted.