Saturday, October 22, 2011

Wires, wires, everywhere

It's cabling not wiring
Rear battery pack cabling complete
Working with 2-0 cable
I finally finished running all the high voltage 2-0 cabling.  This included the jumpers on the battery packs, wiring from the battery packs to the motor controller, and wiring from the motor controller to the motor.  Working with 2-0 welding cable is a different kind of wiring than I'm used to.  You don't just snip this wire and screw it to a terminal.  Just cutting the wire, stripping it, and attaching a terminal is a significant task with special tools.  You also have to very carefully plan how you're going to run the cable.  This stuff doesn't bend like #12 house wiring.  The bends need to be gradual and you have to get the lengths just right.  It was especially tedious to run the two lines from the rear battery packs up to the front of the truck.  That task took a lot of creativity and 1/2 a day.  Most of the time was spent designing and fabricating the clamping points.  The cable needs to be secure without any points where it might rub on a sharp edge and wear through the insulation--that would be an unpleasant event.

Motor controller & DC-DC converter
Welcome to my hood
With the rear battery pack jumpers done and the main lines run to the front I tackled the under-the-hood wiring.  I wanted a breaker on the main line so it was easy to disconnect the power to work on the components.  This turned out to be a non-trivial exercise, again due to the difficulty of working with 2-0 cabling.  I was able to fabricate a bracket to hold the breaker out of 16 gauge sheet metal.  I found a nice plastic box to enclose the breaker at my local surplus store.  Not sure of it's original purpose, but it makes a decent electrical box. Again I had to make a bunch of short 2-0 cable jumpers to complete all the high voltage wiring under the hood.

With the high voltage cabling done, I moved on to running all the low voltage (12v) control wiring.  This was much easier, but still tedious.

Oh what a tangled web we weave
Legacy 12v wiring harness
I now have two major wiring tasks left.  The first is to hook the DC-DC converter up to the legacy 12 volt system for the truck.  The 12 volt system is powered off of the main (116 v) battery pack through the DC-DC converter.  This is not a simple as it sounds.  I'll need only about 20 percent of the old wiring system--just that portion that runs the lights, and accessories. All the wiring for the engine, ignition, alternator, and engine control module can be eliminated.  The difficulty is figuring what wires to get rid of and what to keep.  I've got all the wiring diagrams for the truck, but this is another tedious task.

The last wiring task is to hook up the battery management system (BMS).  This requires installing small circuit board on each battery cell and then wiring them into the BMS.  The circuit boards on the cells measure the voltage of each individual cell and can shunt the charge voltage around the cell once it's fully charger.  The BMS keeps track of the state of charge of every cell and controls the operation of the battery charger.

We'll I'm now going on 6 weeks behind schedule.  I'm thinking I might make a Thanksgiving completion date.

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