Saturday, March 1, 2008

Playing with PakTrakr

Many months ago, I installed a PakTrakr ( to monitor the state of my batteries and it's been acting rather flakey. The PakTrakr consists of several serially connect "remotes" which drive a "display" unit in the driver compartment. The voltage displayed shows the pack voltage and is supposed to monitor the state of each battery and the State-Of-Charge (SOC) for the pack too.

In short, the voltage displayed jumps around quite a bit. The different in voltage jumps correlates closely with the voltage being monitored by an individual "remote" unit, so I'm guessing that the communication link is bad. I contacted Ken Hall at and he suggested adding EMI suppression cores to the links between the "remote" units to cut down on electrical noise. So, I collected a bunch of spare EMI cores from a local computer recycling center and wrapped the remote cables around them. I also put dielectric grease on the connections to see if that would help with corrosion and connectivity. The result: The noise problems got far worse and the PakTrakr display doesn't register anything meaningful.

It's possible the dielectric grease messed up the connections, so I'll try removing the EMI cores and see if I still have the problem. This is not a critical part of the car, but it would be nice to measure the state of the batteries. It turns out that the Zivan charger is doing a reasonable job of over-charging the flooded batteries to keep them balanced. I've only had 50 millivolts of difference between the highest and lowest voltages when I get home from work after 16 miles of driving, so I think the pack is still doing okay. I hope this pack lasts 2-3 years while the costs of lithium batteries come down.

On a slightly non-914ev related note, I'm going to be running for a co-chair position within the Oregon Electric Vehicle Association. If I don't get elected, I'd like to start an open-source EV kit that uses all local businesses to manufacture the custom car parts with freely available designs. We'll see what this year has in store...


1 comment:

Roger Daisley said...

Great idea, Tim: Ubuntu For The Car!
Ps: I've started to drive my VW again, after it sat in the unheated barn all winter, undriven. (You know how cold it gets in Pullman.) I was careful to keep the T-125's well charged. So, far the performance, range & speed, seem unchanged ... good as before. I'm very happy about that! The only thing I lost was the new aux. battery, but Les Schwab replaced it with no quibbling.