The rule for jump starting an EV is the same as for any car: jump the 12V, never the high-voltage pack. The 12V wakes the contactor and the contactor connects the main pack to the motor. Touching the orange high-voltage cables is dangerous and unnecessary.
Why the 12V wakes the car
Every modern EV uses a 12V battery to run the accessory systems and the contactor that connects the main pack to the motor. When the 12V is too low, the contactor stays open and the car appears completely dead. The main pack can still have 80 percent charge, but the car cannot move.
A 12V jump pack designed for EVs connects to the under-hood jump points and pushes enough current into the 12V to close the contactor. The dashboard lights up, the main pack connects, and the car drives normally. The whole process takes a few minutes.
In the Puget Sound, the most common 12V death pattern is a wet 35 to 45F week in an unheated apartment garage. Pre-1980 housing across King County sits at 46.6 percent. Apartment renters in Capitol Hill, Ballard, and First Hill see the most no-start calls.
What you need
A portable jump pack designed for EVs. The pack should have lithium-ion cells, reverse-polarity protection, and at least 1000 peak amps. Standard car jump packs work for gasoline cars but may not have the surge capacity for an EV contactor.
A pair of jumper cables and a donor 12V source also works. A second EV with a healthy 12V can serve as the donor. The donor’s traction pack is irrelevant. Only the 12V matters.
Gloves and eye protection are a good idea. The 12V terminals are not dangerous at the voltage level, but a spark near a battery can vent hydrogen gas. Ventilate the area before connecting.
What to do step by step
- Open the hood and locate the jump points. The owner’s manual shows the exact spot. Most EVs use a positive post under a red cover and a negative ground point on the body.
- Connect the positive clamp from the jump pack to the positive jump point.
- Connect the negative clamp to the ground point, not to the negative terminal of the 12V. The ground point is safer and reduces the chance of a spark near the battery.
- Turn on the jump pack. The dashboard should power up within a few seconds.
- If the dashboard does not power up, the 12V is severely discharged. Leave the jump pack connected for 5 to 10 minutes before retrying.
- Once the dashboard lights up, disconnect the jump pack in reverse order: negative first, then positive.
- Start the car normally. Drive for at least 30 minutes to let the DC-DC converter recharge the 12V.
What not to do
Do not touch the orange high-voltage cables. The main pack is dangerous even when the car is off. The contactor is open, but the pack still holds a lethal charge.
Do not try to jump the main pack directly. There is no safe way to do this from outside the car. Only the 12V wakes the contactor.
Do not use a gasoline car’s 12V as a donor if the cables are too short to reach the EV’s jump points without crossing the high-voltage cables. The risk of an accidental short is real.
Do not connect the jump pack to the 12V terminals directly unless the owner’s manual says so. Most EVs prefer the under-hood jump points.
When to call for help
A driver who is not comfortable with the procedure should call a mobile operator. Operators in the metro carry 12V jump packs designed for EVs and the experience to wake a dead 12V without damaging the car. The call usually takes 10 to 20 minutes on site.
Mobile EV charging covers both 12V jumps and out-of-charge stops. The operator quotes before starting and bills the driver directly. Charge Pro SEA connects you with a local operator who knows the metro. Some models fail more often than others, so if you drive one, read up on Volkswagen ID.4 12V battery failures and what to do next.
When to call
Call (206) 202-7018 when your EV will not start in the Puget Sound region. Charge Pro SEA connects you with a local operator who quotes before starting and bills you directly.