In the Jeep's high voltage (traction) power system, two contactors are used. A contactor is basically a large relay or switch used to switch high current loads on and off. I've chosen the commonly-used contactors made by Curtis/Albright, model number SW202-505. These contactors have a rating of around 400 amps continuous on the high voltage side, and have 12-volt coils which switch them on and off. One contactor is used between the 160 volt Battery Positive (+) and the motor controller Positive (+), and the other is used between the 160 volt battery negative (-) and the motor controller negative (-).
The most positive contactor is also referred to as the "main" contactor. This contactor is mounted in the engine compartment near the motor controller. I mounted it inside a small pocket that is located above the driver's side coil spring bumpstop. This contactor switches the positive wire going from the 160 volt batteries to the controller, and is activated by the controller. The contactor will only be switched on by the Zilla controller after the Zilla has determined it is ok to do so. Should the Zilla ever detect an unsafe condition occuring in the vehicle's drive system, it has the ability to switch off the contactor and disable the vehicle. Thus the controller has the abillity to control its own main power source mechanically.
The negative contactor in this case is also referred to as the "initial" contactor. This contactor is simply switched on and off by the ignition switch. I mounted this contactor to the inside of the battery box under the trunk floor. It is mounted directly next to the most negative traction pack battery. The purpose of having this second main contactor is to provide redundancy for safety. Should something bad happen such as the main contactor getting welded "on", this second contactor will still be there to safely shut off the power.
Circuit Protection (High Voltage):
As with any electrical system, it is neccessary to incorporate a means of protecting circuits incase of short-circuits or overloads to prevent the wiring from melting or combusting (and well, that would be a bad thing). The high voltage systems in electric vehicles usually incorporate a large fuse or Direct Current (DC) circuit breaker. I purchased a fuse instead of a circuit breaker since they are cheaper. The fuse I got is made by Littelfuse and is rated for about 400 amps DC. You may notice that this is lower than the motor controller's rated limit of 1000 amps. However, the fuse is still acceptable is because the input current of the controller tends to be less than the output current, due to the way the controller lowers the output voltage to the motor when not at full throttle. Thus the battery pack side of the high-voltage system in the Jeep's system shouldn't exceed 400 amps for any significant length of time under normal conditions. Even if it does so momentarily, the fuse will not blow right away because it is designed to handle more than 400 amps for a short while (and the higher the current is, the faster the fuse will blow).
The Ammeter Shunt is a device used with an ammeter, or a meter which measures the current flowing in an electrical circuit. The shunt is installed in series in the circuit that is to be measured, and works by creating a small voltage potential across its two terminals as current flows across it. The shunt I am using is designed for 0 to 400 amps DC, and is a 50mV shunt. This means that when a current of 400 amps is crossing the shunt, a voltage potential of 50mV is created, and thus my 400amp/50mV ammeter hooked up to the shunt will readout 400 amps (full scale). The biggest advantage to a shunted system is that you keep the high voltage and currents away from the meter (and out of the passenger compartment).
The shunt is usually installed in the negative side of the high voltage system. I chose to mount my shunt to the firewall, directly above the bellhousing. There was already two bolts sticking out in that area, so I utilized them for a means of mounting the shunt. First I welded together a sort of "U" shaped bracket out of flat steel, which I then mounted the shunt to. Next I marked and drilled holes in the "U" shaped bracket to match the spacing of the two bolts sticking out of the firewall. Lastly, I bolted everything down & wired the shunt. There are two connections for the 2/0 cable of the main negative line, and two small screw terminals where the wires going to the ammeter connect.
"Front to Back" Wiring:
In order for the Electric drive system to get wired up, I needed to have some wiring running from the rear battery boxes to the engine (aka motor) compartment. I could've run the wiring inside the passenger compartment of my Jeep, but this would be somewhat difficult and unsafe. A safer and easier approach is to run the wiring on the underside of an EV because then high-voltage wiring is never present in the passenger compartment.
My Jeep has three distinct sets of wiring that must run from front to back. First, there is the large 2/0 AWG size wire to connect the rear batteries to the front batteries (to complete the series battery circuit). Next, there is a second 2/0 AWG size wire to connect from the negative (initial) contactor to the ammeter shunt (which then connects to the motor controller). Lastly, there is a group of smaller wires which include: a wire from the charger to the positive (main) contactor, a wire from the DC/DC converter to the negative contactor, a low-voltage wire from the ignition switch to the negative contactor, and two low-voltage wires from the "fuel filler" door sensor to the "charger disable relay" which prevents the Jeep from starting/moving while it is plugged in.
I decided to run all the "front to back" wiring under my Jeep, against the unibody's main frame rails. To protect the wiring from the elements, I ran all the wiring in liquid tight conduit. It is the same type of conduit used to run wiring to outdoor electrical fixtures such as lighting, hot tubs, air conditioners, etc. It is gray in color, fairly flexible, and completely weather proof if used with the proper end connectors. In my Jeep, the two 2/0 AWG sized high-voltage wires run in separate liquid tight tubes along the passenger side of the vehicle. These runs of conduit end at fittings which are mounted to the rear battery boxes. The other end of both conduit tubes end at the red Anderson connector located at the passenger side of the firewall. All of the other front to back wiring is run in a single conduit tube that goes from the left side of the rear battery box to a location at the driver's side of the firewall. This conduit is run along the driver's side of my Jeep, right next to the hydraulic brake and clutch lines.
Battery Cables and Interconnects:
All the electrical current going into the drive motor of an EV must first go through the battery circuit. For this reason, the battery circuit is connected up using a rather large size of wire. In my Jeep, I needed to use 2/0 AWG wire size due to the frequent times that I draw as much as 400-amps through the batteries. All wiring that goes from the battery pack to the motor in my Jeep is 2/0 AWG size. This includes the interconnect cables that connect the batteries to one another to form a series string.
In order to be able to work with large wire like 2/0 AWG size easily, you want the wire to be stranded. However, typical stranded 2/0 AWG wire (like the kind used at the electrical mains of houses) is still pretty ridgid because the wire is composed of a small number of large diameter wire strands. For greater flexibility, you want wire that has the largest number of smallest diameter wire strands possible. A type of wire which meets this requirement quite well is welding cable. Welding cable is used in most Electric Vehicles because it is very flexible and easy to work with. As a bonus, many brands of welding cable use a neoprene jacket around the wire which is rated for up to 600 volts and is fairly resistant to abuse and chemical attack. For these reasons, I too chose to use welding cable for all the wiring in my high-voltage traction battery pack.
-work in progress-
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