Now That's a Shunt!

There hasn't been a lot to report over the past few weeks.  I've been dealing with acquiring the hardware necessary for the Air Conditioning system. 

You may recall I'd ordered a Masterflux compressor and controller off a user on eBay for a bargain $200.  The unit was reported to be new but old stock.  In addition it required a 48 Volt DC supply.  I'd been looking for how I was going to supply the necessary current to the controller at the proper voltage.  Well the good news is that I've solved that problem, sort of.  It turns out the compressor was not new, old stock.  It was in fact used and not in good condition.  The compressor had been crammed into the box along with two poorly protected controllers.  Both had sustained damage while in shipment. Why the shipped two controllers, I have no idea.

Ultimately, I didn't trust either controller to work properly, and simply because of the circumstances, perhaps due to guilt by association, I didn't trust the compressor either.  Everything went back. 

Instead I have on order a brand new system that is designed to work directly off of my 160 volt DC system with no modifications required.  The upside is obvious; the downside is it was $1200 more than the other system.  Still, I'd rather spend the money and have a system that works.  I don't want to mess with it once it's up and running.

In the mean time, I've been working on the revised motor mount.  I cut and formed some steel and started dry fitting everything.  Sadly I ran into another road block on this front.  The problem I face is of course one of space.  I need to get adequate shock absorption material under the motor.  without any, it simply lays on the front steering rack with about 1/2" gap between the motor and the sub-frame right behind the steering rack.  I need to support the motor so it's at least 1/4" off the rack so that it doesn't hit it during any vibration.  More space would be better.  The problem is that if I push the motor up too far, I begin to ruin the alignment of the drive line. 

So, I need to find a way to support the motor in the proper position, with the proper attitude, provide shock absorption and tie it to the frame securely.  I could go back with the previous solution I had, but I'd really like to add more shock absorbing material.  The short story is that the pretty solution I drew up in the previous post simply won't work.  Back to the drawing board.

I also started working on a minor part of the A/C system, and that was how to turn it on and off.  The Z3 has a neat little button in the console with a picture of a snow flake on it.  When you depress the button, it glows orange and turns on the A/C.  I tried it out to make sure that it still sends a 12volt signal to the line that previously went to the compressor to turn it on, and no luck.  I don't know if the ECU needed other connections from the wiring harness that are no longer there, but there was no way I could get that to power up. 

Instead, I took the switch out, and started reverse engineering it.  That switch also has the button to turn on/off air recirculation within the cabin.  It has 8 points of connection.  In short order I figured out which blade had power to it when all the right conditions were met; the A/C button was depressed, and the HVAC system fan was on.  I simply spliced a new wire into that line so that I can draw 12V off it to power a new relay.  That relay will turn on power to a fuse box that will provide power to the Masterflux controller and the AC condenser fan and a cooling fan for the controller itself. 

I'm also taking this opportunity to swap out the Xantrex Link-10 meter I've been using, for a Xantrex Link-Pro.  OK, it's actually the e-Xpert Pro; same thing.  Why the change?  You can chalk this up to a rookie mistake.  In the beginning, when I was ordering all the parts for the car, I simply didn't understand how all of the component's specs needed to match up.  I ordered a Zilla capable of putting out 1000 amps, and the Link-10 capable of reading only 500 amps.  As long as I left the Zilla set to a 500 amp output or lower, then the Link-10 meter could measure the current accurately.  If I set the Zilla higher, it didn't hurt the meter, but it simply didn't read the current, which meant the usage it reflected in terms of the battery's state of charge would be wrong. 

Part of the package is a much bigger shunt, one that can handle 1000 amps vs. the 500 amp shunt for the old meter.  Check it out...

It reminds me of Crocodile Dundee, "that's not a knife..."  That thing is huge!  Which raises a concern as to where I'm going to put it.  I think I'll  be able to fit it where the old one was.  I hope.  Fortunately, the meter is exactly the same size and the leads I need to power it and provide data to it are identical, so it's a straight swap as far as that goes.  I did opt for one other thing when I bought the meter, and that is a temperature sensor that I'll be running to one of the batteries.  I'm going to pick one somewhere in the middle of the pack, one that is likely to get the warmest.  In this way I can keep an eye on the temperature of the pack during the summer heat. 

One other thing I've done was to remove the gaps between the batteries I have in the box under the trunk.  I'd put gaps between them so that I could force air between them if necessary.  I had installed a thermal switch that would turn on and force air over the batteries if they reached 125 °F.  It never came on.  Plus with the temperature monitoring I will now have on the meter, it's not really necessary.  But the biggest reason is that I intend to replace all the copper straps that connected the batteries with braided ones.  In order to do so, I need the batteries pushed together. 

So, I pushed all the batteries together and then carefully measured and cut some wood to push into the space created.  Mind you, this isn't to compress the cells, but merely to keep them from moving around. 

You can see it there over on the left hand side.  As I'd mentioned before, and as several people have discovered, the cells do not expand unless you over charge or over drain the, rendering clamping them together unnecessary.