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Short Summary
Main recommendation: To jump start a car safely, connect the jumper cables in a specific order, ground the dead vehicle's negative cable to an engine metal mount rather than the battery terminal, start the donor vehicle first, and then start the dead car with accessories off. The presenter, Len from 1A Auto, also explains that a healthy battery should test at 12.4 to 12.6 volts, and that a running car should show around 14 volts once the alternator is charging the battery. Once the car starts, the alternator should keep it running, so a car that dies after the cables are removed may point to a faulty alternator.
Key Points
- Inspect before jumping: check that terminal ends are tight and cannot pivot, and look for corrosion, which can signal a battery draw and a possible cause of the low charge.
- Batteries typically last about five years, depending on charging system and how often the vehicle is used, and long periods of sitting can drain them.
- Cold cranking amps (CCA) matter because larger engines need more starting voltage; the presenter compared a 525 CCA small-engine battery with a larger-engine battery with higher CCA.
- The alternator, not the donor car's revving, is what charges the dead battery over time, so the car should be driven afterward to recharge it.
- If the car stalls as soon as the cables come off, the alternator may not be producing enough output and should be tested.
Details Worth Noting
- Concrete instructions:
- Wear hand and eye protection whenever working near the battery or vehicle.
- Optionally test voltage with a multimeter first. Connect positive to positive and negative to negative. A healthy battery should read 12.4 to 12.6 volts.
- Connect one red jumper clamp to the positive terminal of the good battery.
- Connect the other end of that red clamp to the positive terminal of the dead battery, working around any corrosion, and clean corrosion if needed.
- Leave the black negative clamp from the good battery hanging/unconnected at first, away from anything that could cause contact or ground out, before later connecting it.
- Do not connect the dead battery's negative clamp to its negative terminal. Attach the final black clamp to a solid, unpainted-looking metal engine mount or ground point, away from rust or debris, and wiggle it to confirm a solid connection.
- Start the donor vehicle and let it run about a minute before starting the dead vehicle, so some charge flows into the dead battery (not to fully charge it).
- Before cranking the dead vehicle, turn off the blower motor, wipers, headlights, and radio to direct power to the starter.
- Once the dead car starts, remove the cables in reverse order: first the black clamp from the engine ground, then the black clamp from the donor battery, then the red clamps, keeping clamps apart so they cannot touch.
- Check the multimeter. A running car should read about 14 volts, and the presenter's example showed 14.36 volts.
- Drive the vehicle afterward so the alternator can recharge the battery over time.
- The presenter notes that some people connect the final negative clamp to the dead battery's negative terminal, but he prefers an engine ground because of sulfuric acid and possible explosive gases near the battery vent.
- Revving the donor vehicle's engine is not necessary; the presenter says the alternator is meant to charge the battery after starting, not provide a large starting burst.
- The presenter says a battery that is too low after parking may not restart, so a car that appears to run only on battery power may still have an alternator problem.
Bottom Line
Jump starting works best when you protect yourself, use a solid engine ground, and let the alternator finish the job by driving the car afterward and checking whether it keeps running once the cables are removed.
