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Safety First
As the number of hybrid and electric vehicles (EVs) on the nation’s roads grow, it is likely that more EVs and hybrids will come into your shop. Hybrids and electric vehicles are equipped with a battery pack with up to 800 volts, which is in sharp contrast to a conventional vehicle with an internal combustion engine that only has a 12V battery. The high voltages associated with electric and hybrid vehicles means that shop safety takes on added importance when working on these vehicles.
For some repairs, it is necessary to disconnect the high-voltage battery before completing the job. Performing a live-dead-live test is the best way to ensure that the high-voltage battery is disconnected.
Safety Equipment
Before disabling the high-voltage battery on an EV or hybrid, be sure to have the necessary safety equipment. Remember, you’re dealing with voltages that are high enough to be lethal and this equipment will help protect you.
Digital Meter
You’ll need a meter with a Category 3 or 4 voltage rating that has insulation inside that can endure an extended connection to a high voltage system.
High Voltage Gloves
Class 0 electrical insulating gloves will keep you safe while working on an EV. The two-piece design features rubber gloves and leather gloves. The rubber glove gives the primary high-voltage protection while the leather outer gloves protect the rubber gloves. Look at the manufacture date on the gloves, they are good for six months after that date before they need to be replaced.
TIP: To ensure that the rubber gloves have no holes and are safe to use, trap some air in each glove and roll up the cuff tightly and check to make sure that it holds air. A hole in the glove could allow the high voltage to get through to your skin.
Rubber-Soled Footwear
Wearing rubber-soled shoes or boots when working on electric vehicles gives protection from electrocution. Rubber acts as an insulator and breaks the circuit to the ground so you don’t conduct the shock current through your feet.
Safety Glasses
As with conventional vehicles, safety glasses give protection from fragments of metals, and splashes from oil, grease, chemicals, and other fluids.
Steps for Disconnecting High-Voltage Battery in EVs
Critical to ensuring that the hybrid or EV is safe to work on, doing the live-dead-live test after you have disabled the battery verifies that the voltmeter that you’re using to test the battery voltage is functioning properly.
TIP: Before working on an EV, consult the service information to determine if the repair or service you’re doing necessitates the high-voltage battery to be disconnected.
Step 1
Turn the ignition key off and put the key fob away from the vehicle. If you can start the vehicle, move the fob further away. You don’t want the vehicle accidentally starting while you’re working on it.
Step 2
Disconnect the 12V battery on the negative lead. Loosen the nut then push the cable away so it can’t accidentally tough.
Step 3
Wearing high-voltage safety gloves, disconnect the orange service plug on the high-voltage battery case. Put the plug on the workbench so it is out of the vehicle.
Step 4
Wait 10 minutes; it can take up to 10 minutes for the capacitors in the system to fully discharge.
Step 5
Follow Live-Dead-Live safety procedure to ensure the high-voltage system is disabled.
Step 5
Follow Live-Dead-Live safety procedure to ensure the high-voltage system is disabled.
Live
Ensure that the voltmeter is working by touching the leads across the 12V battery. If it registers 12V, you are assured that the leads are good, and the meter is on the right scale.
Dead
Check that the high voltage is disabled. Wearing the high-voltage safety gloves, remove the power inverter cover to get access to the high-voltage terminals. Take the voltmeter and test for voltage on the two high-voltage terminals; it should show 0 volts, meaning the system should be safe to work on.
Live
The final step is ensuring that the meter is working properly so you are assured that the results on the high-voltage terminals was accurate. Test the voltmeter on the 12V battery once again to verify that that it registers 12V. Once you verify that the meter is working, you can start working on the vehicle.
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The content in this article is for informational purposes only. You should consult with a certified technician or mechanic if you have questions relating to any of the topics covered herein. Tenneco will not be liable for any loss or damage caused by your reliance on any content.