Yes, You Can Jump Start With An EV
I always urge some caution and remind people that it's not a sin to consult the instruction manual.
EVs have a 12v battery, just like any other car, and if it's flat, then you are stranded.
However, as an auto electrician, this is my standard procedure for safely jump-starting any 12 volt car system, be it EV or ICE.
- Start by identifying where you can get a good solid connection to the 12v system on both vehicles. It may be on the battery itself or there can be an accessory terminal or dedicated jumper point.
- Connect your two vehicles using jumper leads.
Positive to positive first, making sure the clamps don't touch any other metal parts of the car.
Negative to negative second.
Reverse order when disconnecting. - Start up the "good" vehicle. Whether it's ICE or EV the donor car will now charge both 12 volt vehicle batteries. (cars can charge quickly, they easily put out 10 times the charging current of a plug in the wall battery charger)
- Wait for at least 10 minutes while the "bad" car soaks up some charge, and check that the connections you've made with your jumper leads aren't getting too hot to touch in the process. (depending on the connection, cables and battery state of charge, there could well be 50 amps or more flowing)
- Turn the "good" car off and then disconnect the jumper leads
- Start up the "bad" car.
If the battery is serviceable, then it should crank an ICE engine or initialise an EV system.
If it doesn't work, then you shouldn't be trying to drive a car with a completely failed battery anyway.
Tips for finding the battery terminals
Under the bonnet of this car, there's a fuse box. Remove the lid, flip open the red cover marked (+) and connect your charger or jumper leads.
RED for Positive
Black for Negative
The negative lead can be connected to any substantial metal part of the car, like a strut tower bolt or part of the engine. Avoid aluminium pipes that may be part of the air conditioning or power steering system.
In this vehicle, the battery is impossible to get to without using a screwdriver to remove the boot floor.
If you could access the positive battery terminal, the boot latch at the bottom of the frame would be a perfectly good connection point for the negative lead.
Note in the image below the brake and air-conditioning pipes circled are not suitable for connecting electrical leads.
Battery terminals are different sizes. Negative is always smaller than positive. Do not reverse the connections.
Two Safety Messages
DO NOT TRY TO CRANK AN ICE ENGINE USING AN EV DONOR CAR.
- 12 volt EV batteries are not designed to deliver large amounts of current (hundreds of amps) in a surge
- Simply use the donor car to charge the flat battery
DO NOT DISCONNECT YOUR JUMPER CABLES WITH EITHER CAR TURNED ON
- This is the standard for any jump starting procedure. Cars can deliver large currents while charging, which means damaging voltage spikes can be created, and sparks thrown, if live connections are broken.
- While less common these days, car batteries are traditionally flooded lead acid chemistry. When being charged they create explosive hydrogen gas, so avoid making sparks.
- If your 12 volt battery has been charged by another vehicle for 10 minutes, your car should start itself without jumper leads connected.
- If it doesn't then the battery is likely open circuit or has a failed cell, which means it's too badly damaged to use. The car electrical system relies on the battery to give it stability, without the buffer of stored energy available, just using the brake lights can be enough to cause a dip in voltage which will shut the car down.
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