High-Voltage Cabling and Disconnects

that follows the battery. This approach eliminates the recalibration and configuration of the charger with new charging data profiles based on manufacturer, new/old battery chemistry, and compatibility.

Charging of a battery with minimal built-in intelligence is quite analogous to an infant being fed by its mother. The reaction of the infant during feeding determines whether or not the mother provides additional food. On the contrary, the intelligent battery can inform the charger as to how much additional charge or discharge is required to maintain optimal performance of the traction battery. The battery diagnostics information is transmitted using the smart HSD bus. The diagnostics battery pack information sent to the BMONs includes battery type, serial number, manufacturer’s name, and manufacturer’s date.

In addition, EV service stations can download battery pack charging data. This data is useful to locate the fault and initiate a corrective action for:

• Conditioning or repair of battery modules • Replacement of faulty battery components, including connectors, fuses, and wiring • Replacement of an entire battery module

In addition, the intelligent battery pack information sent to the BMONs includes battery cycle count, vehicle driving profile, or driving pattern.

HIGH-VOLTAGE CABLING AND DISCONNECTS

EVs have two different wiring systems: high-voltage and low-voltage. The high-voltage wiring system is used primarily to provide energy to the motor to propel the vehicle. However, some vehicle manufacturers use high voltages to power heating/cooling systems, power steering pumps, and EV sensors. The Society of Automotive Engineers (SAE) has specified that orange cables are the standard color for high-voltage wiring in EVs.

At present, EVs have high-voltage systems ranging from 250 to 360V DC and in some cases even higher. The high traction voltages are provided by battery packs composed of dozens of individual batteries wired in series and sealed in protective cases.

A separate 12V auxiliary battery is part of design. This auxiliary battery is used for accessories such as vehicle instrumentation, lighting, and HVAC. A separate 12V battery is kept charged by a DC-to-DC

converter that steps down the voltage from the high-voltage traction batteries.

In EV designs, major automobile manufacturers use isolated electric busses for both the positive and negative sides of the high-voltage electrical system. This is an important safety feature. In the event of positive electric bus isolation loss with respect to the vehicle frame or chassi, no electrical current passes through the vehicle frame or chassis. As a result, vehicle drivers or emergency responders will not be subject to a hazardous shock by the accidental loss of isolation between the positive or negative electric busses with respect to the vehicle frame or chassis. The EV system design differs from internal combustion EV systems because the 12V DC system relies on the vehicle frame and chassis as the negative electric buss. This is an acceptable wiring design because people are not exposed to lethal voltages or currents with 12V DC systems.

In addition, all OEM EVs have automatic high-voltage system disconnects as a primary safety design feature. These automatic disconnects include a combination of ground fault monitoring, an inertia switch, and/or a pilot circuit.

Ground fault monitoring disconnects operate on the same principles as the ground fault monitoring devices used in everyday households circuits. These devices monitor the ground system in the EV for current leakage from the high-voltage battery pack. If a fault in terms of current leakage is detected, the devices automatically disconnect the highvoltage system from the battery system. The location of the ground fault monitoring system varies with each vehicle design, but it is typically in the vicinity of the traction battery pack.

In the case of EVs that use the inertia switch disconnect, the end result is the same but the method of isolation is slightly different. The inertia switch senses high-deceleration rates such as those encountered in a vehicle accident. In the event rapid deceleration occurs, the inertia switch is automatically tripped and the high-voltage system battery pack is disconnected from the rest of the EV. The inertia switch is set for a low impact. Inertia switches are also common on internal combustion engines and are used to de-energize electric fuel pumps from the engine in the event of an accident. In most cases, the inertia switch can be reset by pressing a button located on the device. Although the location of these switches varies based on vehicle design, most are located in the motor compartment.

Other vehicles use pilot circuit disconnects; again, the end result is the same, but the mechanism is entirely different. Throughout the motor compartment, high-voltage cables are routed between the battery