Friday, January 23, 2009

Finishing the Guages, Link-10

I worked all day to get the tach sensor fixed and the link-1o installed.

Here's my solution to fixing the tach sensor. I'm using a stainless steel bolt to hold it in (which is just barely magnetic). I'm also using a salvaged plastic gear as a non-magnetic spacer to put the spinning magnet disk inside the sensor housing.

At first the gear was too thick and the head of the bolt rubbed against the inside of the sensor housing. After filing the gear down to 1/4 inch, it seems to work well, even under acceleration.

In hooking up the system, I cheated a bit and pulled the positive 144V tap needed for the Belktronix system off of the other side of the main circuit breaker. This saved a bit of wiring, but (as always) ended up biting me when I wired up the Link-10. This is a picture of the Airpax circuit breaker under the car. The 144V tap is coming from the rear battery pack is on the left post. I added a 16 gauge wire to this post and ran it into the engine compartment to attach to the Belktronix system and the link-10 connections. This allows the breaker to blow and also let me disable the system without losing power to the link-10.

Here's installing the 500 amp shunt for the link-1o meter. I have just a little space left on the driver side chassis. Just above the shunt are two silver-looking indentations aligned vertically. Those are the marks I made with a 3/16" drill through the mounting holes in the shunt. I used those to drill some holes and insert two 8-32 threaded rivnuts.

Here's the shunt mounted into place with the 8-32 bolts in the installed rivnuts.

When I had the car running before this, I simply had a negative battery cable from the Belktronix controller running directly to the negative terminal on the battery. With the shunt, I now break this path and use two cables, with the shunt in between. While your mileage may vary, I cut welding cable 9 1/2" long for the battery post to the shunt and 13 1/2" long from the shunt to the controller negative terminal.

Just under the 2/0 cable bolted to the shunt, you'll see a piece of four-twisted-pair cat5 cable. The link-10 requires a twisted pair of wires from the shunt to the display to reduce noise. Since there are only three other connections going to the display besides the one twisted pair, I decided to combine the other three twisted pairs into single wires to carry more current. The combined brown pair goes to link-10 pin 1 (negative terminal). The green twisted pair takes the differential signal from the shunt (link-10 pins 2,3). The blue combined blue pair goes to link-10 pin 4 (high voltage prescaler output) and the orange combined pair goes to pin 5 (7watt DC-DC output).

Here's everything wired up. The shunt is wired and I found some space for the Belktronix DC-DC and Link-10 prescaler beside the engine mount. Note the filler cap for the washer fluid. I'll have to be careful filling this since the washer fluid is somewhat conductive.

Yay, the link-10 works and tach above it as well. After reading the manual and setting some parameters, it seems to work fine. I used the following for my system:

  • charging end voltage: 172V
  • Peukert Constant: 1.11
  • amp-hour capacity: 100

I still have to configure the tach shift light to stop the motor from over-revving. I'll get to that tomorrow.

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