I spent most of yesterday and a few hours today wiring up the PakTrakr system. It's a bit of a pain to disconnect the most negative lead before attaching the display, but that's minor nuisance. It seems to measure pack voltage well; however, the voltage measurement on each battery seems to be slightly inaccurate. The Zivan charger is balancing the batteries well and each of them is within an 8.48V-8.50V range (20mv difference is pretty good!).
I chose to mount the display on the central console as shown above. It doesn't have a backlight but is easy to read during the daytime and the placement makes the buttons easy to access.
I had to greatly extend one of the PakTrakr remote module cables so that the rear battery pack could talk to the remote modules in the front of the car. That involved cutting one of the 3-wire cables on one remote module and splicing in an 8-foot extension of additional 3-wire cable. I added heat-shrink tubing to make the splices clean so they could be pulled through the right-hand heater duct under the passenger-side door.
The system seems to work fine. Having a backlight would be nice, but not necessary. My biggest gripe is that double sided tape seems to have a big problem sticking to the back of the PakTrakr modules, even though they tell you to use it to mount the modules.
On a downer note, the CCPower DC-DC converter blew again (fuse was vaporized and FETs shorted out). I actually caught the system in a working condition just before driving home and found out that it had blown when I got home. The only difference was that the DC-DC converter was under a heavy load on the drive home because the headlights were on.
Based on the circuit inside the DC-DC converter, I suspect that there is a significant amount of current (required from the headlights) going through 144V side. When the FET opens, the current rushing through the inductor causes a high voltage spike (300-400V is not unheard of) that gets added to the +144V side and just wipes out the 500V FET. I'll have to double check to see if the inductive kick-back diode is properly functioning. The CCPower website only has the input voltage of their DC-DC converters listed as 80 volts so, although these are designed for EVs, the underlying design may not be able to handle the higher voltage, especially with spikes from regenerative braking.
In the meantime, I'm using a 12V charger to charge the accessory battery as well. Maybe I can integrate that into the overall charging circuitry when I plug in the car.