Boosting a Dead Battery With A Donor

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boosting a dead battery
Jump Starting: Photo by Longhair: CC 2.5

Murphy’s Law dictates you will hear your auto engine clicking only in the dead of winter when it is freezing cold. You see batteries are a bit like teenagers: They prefer to sleep in, on cold winter mornings.

The clicking is the starter failing to engage because the battery is too weak to do its job. If you can’t locate an auto electrician, try boosting a dead battery with a good Samaritan’s help.

The lead acid battery is not completely dead. It can still deliver a spark, or a shock if you mishandle it. You could damage electronics on both cars if you connect the jumper cables in the wrong sequence. Wear gloves and eye protection. That gunk around the battery terminals can burn your skin. Wash your hands / use wet wipes afterwards, or if you feel a tingle while boosting a dead battery.

Switch Off and Connect the Booster Leads

Bring the donor vehicle close enough to the flat battery car. Turn the ignition off in both vehicles and check the condition of the jumper leads. DO NOT proceed if insulation is missing or any clips are loose. You do not need a spark while boosting dead car batteries.

#1 Clip one end of the red lead to the DEAD battery positive terminal

#2 Connect the other end to the DONOR vehicle positive terminal

#3 Connect the black lead to the DONOR battery negative terminal

#4 Clip the other end to a suitable earthing point on the DONOR vehicle

The two black ends should be AS FAR APART as possible on the donor vehicle. DO NOT connect the black wire to the receiving vehicle, as this could cause a spark, or an explosion if a faulty battery is leaking.

The Procedure for Boosting a Dead Battery

boosting a dead battery
Cable to Positive Post: Wtshymanski: P Domain

Start the donor vehicle and allow it to idle for two minutes. Increase the engine speed as if you were driving at 40mph in top gear. Have an assistant attempt to start the receiving vehicle by simply cranking the starter. If the engine fires up, well and good: If not, the receiving battery is truly dead.

If the receiving vehicle starts, allow both vehicles to idle for two minutes. Then disconnect the jumper cables in reverse order, taking extra care none of the clips touch. Take the receiving vehicle for a half hour drive. Find a battery supplier at the end of this journey, or store the vehicle in a warm place until you can.

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Preview Image: Day 220: Jump Starting

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About Author

Electricity has always intrigued me. I have been writing about batteries and energy storage for more than ten years, and have published over 4,000 articles on this website. During that time, I have researched developments across lead-acid, lithium-ion, sodium-ion, flow batteries, and emerging energy-storage technologies. My goal is to explain complex battery concepts in clear, practical language that anyone can understand. My writing career began unexpectedly after leaving the corporate world. What started as a search for a new direction gradually became a fascination with batteries, renewable energy, and the science that powers modern life. Writing may not have made me wealthy, but it has given me the opportunity to explore an industry that continues to evolve in remarkable ways.

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