Isolating High Voltage

There are a number of ways to shut down and isolate the high voltage components in all hybrid vehicles. First, turn the key to the “off” position and remove it, or disable the keyless start. Ensure the fob is out of range of the vehicle.

If there is a situation where you literally have to handle the cabling, or it has become damaged, extra steps should be taken. The checks and balances that are in place should keep you safe, but it’s best not to bet your life on it. If a car has flipped five times into a ditch, don’t assume potentially damaged technology will work.

The first order of business is to disconnect the 12V lead acid battery.

The capacitors have the ability to store energy for up to 10 minutes, so it’s best to wait 15 minutes to ensure complete discharge.

After 15 minutes, put on insulated gloves rated for at least 1000 volts. If there are sharp edges or shrapnel, use leather overprotectors with the insulating gloves. Most insulated glove manufacturers recommend or require visual inspection of insulated gloves before each use as well as the use of overprotectors at all times.

Now it’s time to directly shut down power for the high voltage (HV) system.

All HV shut-down components are connected to high voltage cables or components, which is why the insulating gloves must be worn. Each component location is different, depending on the vehicle manufacturer, but it should be easy to determine. They usually reside near or on the battery bank, in the trunk, or under the hood. Check the owner’s manual for location information.

To shut down the HV system, Ford, Toyota and Lexus require you to remove an HV service plug. Honda requires that you turn off an HV safety switch. There are also HV fuses in some models that can be removed.

When you disconnect the 12V battery, assuming the system is working as designed and there are no faults in the system, it will automatically isolate the HV battery pack. Taking the extra step of removing service plugs and fuses and turning off safety switches is to ensure that the system is completely shut down if things aren’t functioning properly.

Once these steps have been taken, there will be no electricity within the HV cables or capacitors, and the generators will be removed from the system. The HV battery bank will still contain its charge, but will be completely isolated from the rest of the system.