For Want of a Nail

So near yet so far.

Yesterday was focused on completing the battery pack area in the rear under the hatch. There was a good bit of fabrication involved and I'm really pleased with the results. 

First, the Nissan master disconnect/fuse unit was installed on the left of the pack.

 Then the DC/DC Converter control box with fuse and AVC2 charge control on the right. The red circular device on the edge is an inertia switch to shut off power in the event of an impact. The little red thing sticking out behind it is a switch for the enable signal. I connected the normally closed terminal of the AVC2 relay to the enable line of the GEVCU to prevent driving off with the charge cord attached. Turning off the enable switch will prevent the car from running. It's a rudimentary security feature, and our little secret. 

There is more hiding beneath this shelf: the mid-pack contactor and a terminal strip to connect the J1772 charging port with the charger and controller. The spaghetti will be out of sight down here.

Viewed as a whole, I think the battery bay looks tidy and businesslike.

With all the cabling in place, it was time to power up. Just as I turned the switch, there was a clap of thunder outside and I couldn't help thinking ...

All the pumps were pumping and pack voltage read correctly when turned on, then showed zero when off. Charging started up when the J1772 was plugged in. All good. So I went off for a late celebratory supper with plans to finalize the configuration in the morning and maybe take the first spin around the block.

Alas, was not to be. I calibrated the throttle and power cycled the GEVCU, but noticed that my multimeter was still showing full pack voltage when the system was turned off. Not good. Last night it was zero, now full pack voltage and dropping slowly, eventually getting into the millivolts range. It occurred to me that I was watching the capacitors in the DMOC drain which must mean that the contactors were still closed. Something awry with my precharge routine? I pulled the rear contactor and it checked fine.

Then I pulled the Better Place contactor module and found that the contactors were both locked in the closed position. Contacts welded shut! The GEVCU manual has a full chapter on precharge considerations, and my setup worked as it should last night. What happened?

Here's the culprit: sorry it's out of focus, but you can see the chunk of insulation that's missing. This is the common +12 volt connection for both contactors and the precharge relay. The GEVCU manages the startup sequence by opening first the precharge relay ground line, then the main contactor's ground after the capacitors have reached pack voltage, avoiding the inrush surge current that welds the contacts closed. What changed?

The yellow circle highlights the connection for the wire above. This particular wire was a bit too short to connect with the +12 volt terminals at the left of the box, so I connected it to the normal input side of the diode. Good +12v there, but a rather awkward placement - notice that it passes over the top of the output terminal on the charger side of the diode. I must have nicked the wire when I installed it, and then the bare wire made contact with the charger power output screw. When I plugged in the J1772, power passed through that screw to the contactors without the GEVCU managing the connection. Result: inrush current and welded contacts. I've ordered a fresh contactor, precharge relay and resistor. UPS should deliver them early next week, so all is not lost. Unless, of course, there is collateral damage to the GEVCU, but won't know that until later.

For want of a nail the shoe was lost

For want of a shoe the horse was lost.

For want of a horse the rider was lost.

For want of a rider the message was lost.

For want of a message the battle was lost.

For want of a battle the kingdom was lost.

And all for the want of a horseshoe nail.

Circuit Box

Three very long days in my 90+ degree garage have put the project ever closer to it's first test drive. 

That tangle of wiring at the back of the inverter is finished save for one wire to the reverse switch. 

It looks like total chaos, but there is a method to the madness. The relays (clockwise from the upper left) control the 12 volt switched ignition, power steering pump, heat exchanger fan, and charger. Almost invisible above the charger relay is a dual power diode that enables what I hope is a clever way of automating the charge process. I can't test that until the rear wiring is done (tomorrow, if all goes well), but in theory, it's very cunning. I have been able to test the power brake vacuum pump, power steering pump, and coolant pumps, and all are spot on! I do plan to put a cover on the circuit box so it looks neat and tidy.

The vacuum pump has its own relay and wiring jumble. Yesterday I solved the mystery of how and where to hook up the vacuum lines to get the air conditioning flap to operate. Once it did, it moved an impressive amount of air, and will need to be somehow integrated with the aftermarket AC compressor. That's for another day.

The 12 volt battery feeds an eighty amp breaker that serves all the EV circuitry and provides a single shut-off point. The 50 amp fuse on the left protects the power steering pump. With the battery pack cabling ahead tomorrow, along with the remainder of the charging support, we are closing in on a first test drive. Keep checking in ...

Wiring the Motor Bay

Spent the day routing wires and organizing the split loom to keep things neat and organized. Started by wiring the power steering pump and aggregating with the cooling pump wiring for a single loom into the circuit box.

After cutting the high voltage cable to size, I crimped on the lugs and installed the contactor module. 

The GEVCU is mounted to the rear of the inverter and excess cable is coiled on the coupler housing below it. Other wiring is tagged and ready to be connected to the GEVCU harness.

The charge controller is mounted to the front of the inverter and all connected to the charger.

The fan wiring is consolidated with the charger and throttle wiring, then routed to the back of the inverter where it will be fed with all the other connections into the circuit box.

Meanwhile ...

Robert has been painting up a storm. These all look great, and I'm afraid the rest of the car will need the same treatment down the road a bit.

Robert mentioned that I really should get the headlight covers painted as well so they match. He's right, of course, so I pulled them off the car and took them over. The car will look fantastic!

Robert also finished out the top cover for the coupler housing, so I picked that up and spent nearly all morning installing it. It's in a very awkward place with no room to swing a wrench, so four bolts took way too long. It had to be done now because the GEVCU will be  mounted over it and it will be even more obscured with all the cabling that goes along.

The afternoon was spent on an equally fussy project, fabricating and installing the charge port. Again, working in the hatch behind the former gas filler is an exercise in contortion, but the payoff is a really pretty piece of bling.

Along with those two major projects, I finished installing the GEVCU and Charge Controller now that the paint has dried on the mount box, and started gathering the under hood wiring into split looms for connection to the GEVCU harness in the circuit box.  

Building Better Boxes

A couple of nights ago I woke up at 2:30am with a brilliant idea that came to me in a dream. OK, maybe not so brilliant, but gives you some idea about what I've been dreaming about lately. It actually made sense the next morning, and had nothing to do with Dilithium Crystals, Gigawatt Transformers, or Ancient Aliens.

I have not been happy with the contactor box being in the rear of the car with the battery pack. I had already run high voltage wires through the passenger cabin along with the control wiring, which made me nervous. It just wasn't right.

I had wasted the better part of two days trying to find a space in the motor bay, but they were either too low and subject to water splash, or too precariously fragile. 

Here's the dream: (In the voice of Charlton Heston) Build ye a box around the inverter, and behold thy contactor module may be affixed thereto. Yea, verily I did proceed to do just that, using pressure treated exterior 5/8" plywood that was left over from the evTD project. Some scrap aluminum angle and a treaded rod to hold it all in place, and that's the box. With some T-nuts and three bolts, it's a comfortable fit in the space between the inverter and the coolant catch tanks with all the plumbing below.

The contactor module was included with the Better Place battery pack and contains the positive and negative contactors along with the precharge resistor and control relay, all nicely integrated. It has the connections for the high voltage wiring from the battery pack and output connections for the inverter.

The front of the box will mount the charger controller and the GEVCU system controller will mount on the back. The GEVCU manages a whole range of car functions in addition to the motor speed control, and needs a way to connect a bunch of wires in some orderly way.

I had spent hours laying on my back under the dashboard in a contortionist pose that would would make Cirque de Soleil proud. I found and removed what Porsche calls the "Digital Motor Electronic Control Unit". Just as I suspected, once it was disconnected, the basket of snakes under the hood slithered off. All that messy wiring was there to feed sensor information about the gas motor to the ECU so it could fiddle the timing and fuel injection. After hours of searching, I finally found the switched 12 volt wire, a single wire among the seven bundled into the cruise control harness. With all of that gone, the motor bay is a much neater place.

So now the electric motor needs the same sort of inputs and outputs, so a circuit box was built and mounted on the top rear of the inverter. Four relays and twenty six terminal connections will be centrally housed here with all wiring entering and exiting through the open back. I think I'll put a hinged lid on it for easy access later.

A coat of black paint will make the whole apparatus disappear, then I can mount the components and wire everything up. That should basically finish the under-hood activity and we'll move on to the back. Tomorrow is another day ...

Perfect Spot Redux

Remember that perfect spot I found for the high voltage fuses a couple of days ago? It had a couple of threaded openings in the strut mount, easy access and clearly designed for the fuses, right?

Well, turns out it was also the perfect spot to mount the throttle. It was right in line with the accelerator cable and just the right distance away. It allowed a gentle angle for the cable and once in place, very good feel for the pedal.

I'm once again using the Evnetics Throttle Pot. I used it on the eBugeye and the evTD. It has been bulletproof and easy to set up using the existing pedal and cable. Unfortunately, Evnetics has moved on to other markets, so this may be my last one.



Working around the aluminum mounting plate, I snagged a finger on the sharp edge (ouch) so I added some door edge guard strips to make it "finger safe". Makes the whole installation look pretty neat.

So what to do with the fuse mount that got displaced? Found another perfect spot for it with another threaded opening, this time on the frame rail. I had to employ the "wire stretcher" since the new mounting point is a bit father away from the firewall. It looks like it was designed for the spot as well with the added bonus that it's within easy reach of the charger cable. The other fuse will attach to the air conditioner positive cable. I used fairly stiff 6 gauge wires to span the distance to the battery pack under the hatch and the high voltage wires from the charger and A/C compressor appear to be 10 gauge, so once again, overkill is always appropriate.

Cool, Man!

The cooling system is complete. The plumbing is a hybrid of 3/4" heater hose and elbow fittings to connect the catch tanks, pumps, motor, and inverter, 5/8" heater hose for the charger with 3/4 to 5/8 adapters, and AN8 hose and fittings to and from the heat exchanger.

Starting with the forward pump, there's an elbow to get the hose pointed at the charger and a 3/4 to 5/8 step down to get the correct size.

Notice the AN8 fitting and return hose from the heat exchanger. 

The 5/8" hose charger inlet is on the right and the outlet is on the left,

looping through another 3/4 - 5/8 step up sleeve and elbow into the motor inlet. 

the motor outlet leads to an AN8 adapter

that connects to the heat exchanger.

The heat exchanger is a dual core Derale unit with the upper core serving the motor and charger cooling loop and the lower core taking care of the DMOC inverter. The inverter had to be removed to install the plumbing on the front of the motor.

While the inverter was out, I decided to rotate it 180 degrees to get the plumbing connections on the same side as the pumps, primarily to free up space on the opposite side for the air conditioning compressor fittings. You'll see soon why that was necessary.

Unfortunately, that meant I had to chop up the artistically curved underside of the mount to get clearance for the protrusion on the bottom of the inverter. My grinder skills pale in comparison the Robert's, but what it lacks in grace and beauty, it makes up for in utility. The good news is that after the inverter is connected to the motor and secured, the mount will be out of sight.

With the inverter and its cooling loop installed, you can see that if the inverter inlet and outlet had remained on the opposite corner, it would certainly have left no space for the A/C fittings. As it is, it leaves scant clearance for the power steering pump. If it seems that there an awful lot of hose clamps, there are! The cooling system used twenty five clamps in addition to the ten I also installed today on the power brake vacuum lines.

I set up my test rig to make sure all those clamps were doing their job. Good news - no leaks!

The systems took almost a gallon of coolant, and after about a ten minute run, all the air bubbles seemed to have worked their way out. I was most pleased that the time I spent last month calibrating the PWM signal generators paid off. Those tiny controllers held their settings and ran the pumps at about half speed in near total silence. I've since learned that the pins exactly match a three pin computer fan cable. That will make for an elegant installation that, again, no one will ever see.