UniEnergy Technologies Battery » How to Jump Start a Car With a Spare Battery? (10 Steps & Expert Tips)

How to Jump Start a Car With a Spare Battery? (10 Steps & Expert Tips)

A failing car battery is one of the most frustrating things any driver can experience. No matter how much you turn the keys, your car won’t start. And if you’re far away from a mechanic, you might think all hope is lost.

That is, until you realize how easy and effective a spare battery can be to charge your car. Don’t worry – you don’t need much, if any, mechanical skill to pull this off. All you need are some small pieces of equipment and the correct method to restart your car.

In this article, we’ll run through step-by-step how you can jumpstart your car with the help of a spare battery. We’ll also highlight simple but effective ways to maximize your battery’s life and ensure your extra battery is kept in good health to help you in a future jam.

10 Steps on how to jump start your car with a spare battery

10 Steps on how to jump start your car with a spare battery

Using a spare battery to jumpstart your car is somewhat similar to using the battery of a second car. There are specific guidelines on how to connect and disconnect cables and essential safety precautions you must respect to perform the task.


  • Safety glasses & rubber gloves
  • Wire brush
  • Set of jumper cables
  • Spare battery

Step-by-step Guide

  1. Put on protective gear, including eyewear and rubber gloves.
  2. Open up your car hood and locate your car battery. Inspect it for any signs of corrosion, dirt, or debris that could prevent it from starting.
  3. Use a multimeter to check if your spare battery has enough power to jumpstart the car. Twelve volts should be adequate.
  4. Get your spare battery and space it close to your car’s battery. You don’t want too much distance between the two when connecting them.
  5. Identify the positive terminal (usually red and with a + sign) and the negative terminals (typically black and with a – sign).
  6. Clamp one end of the jumper cables on the battery’s positive terminal of the dead battery with the positive terminal of the spare battery.
  7. Next, clamp the black clips of the negative terminals with that of the spare battery. If cables are not correctly aligned, sparks may appear.
  8. Now, go into the driver’s seat and try to start your car. It would be best if you let the engine run for a couple of minutes before you turn off the vehicle and disconnect the cables.
  9. It’s important to remember to disconnect the cables in reverse order –disconnect the negative terminals first and then the positives. This prevents a short circuit from entering your car’s electronics.
  10. Drive your car for 30 or so minutes to allow the battery to recharge.


What if your car doesn’t hold its charge?

The first thing to do is inspect the connections of your car. Perhaps there’s a slack cable or a loose nut that’s not connecting correctly. Use a wrench to tighten connections together gently – don’t apply too much pressure, or they might crack.

Additionally, check the battery terminals (and the surrounding areas) for any signs of corrosion. Even the presence of moisture can be a cause for concern. Using a wire brush or dry cloth, expel debris, which in turn can help improve the battery’s connectivity.

What if your battery repeatedly dies?

If your car battery continues to fail every couple of days, despite being jumpstarted, this can point toward more severe problems within your car. There could be a fault within the electrical system, your alternator could be damaged, or your battery may finally be beyond saving.

Gently loosen the bolts holding your battery in place, and e detach the terminals one by one, ensuring they do not come in contact with metal surfaces. Inspect your battery for any signs of corrosion, test its voltage with a multimeter and refer to the car’s manual when a replacement battery is necessary. On average, car batteries last between 2-3 years before requiring a total replacement.

Is your battery or alternator the problem?

Many drivers falsely assume there’s a problem with the battery, and despite many attempts to recharge or replace it, the car still refuses to start. But sometimes, your vehicle may fail to start if its alternator becomes damaged.

Unfortunately, it can be difficult to distinguish if your alternator or battery is the culprit. If your battery is at fault, your car may have a battery warning light on the dashboard. Check your manual for specific instructions on this feature.

A common sign of the alternator being at fault is if the car starts, but electronics like headlights and dashboard LEDs are dimmer than usual.

What type of cars can be jumpstarted?

Most cars can be jumpstarted. If in doubt, consult your manufacturer’s manual. In the case of hybrid cars, you should always use a compatible spare battery to prevent the vehicle from overloading. Generally speaking, a 12V battery will work in most scenarios.

Are there any safety precautions?

When working with an exposed car battery, you must prioritize your and your car’s safety.

An exposed flat battery can still with it potential electric dangers; as such, you must wear non-conductive materials, including rubber gloves. Additionally, jumpstarting batteries have the potential to cause tiny sparks. While this is normal, sparks can damage your face, ignite nearby gaseous materials, and cause an explosion.

As such, jumpstart your car in a safe, clean, open environment free from potential hazards. Never wear loose clothing, necklaces, bracelets, or hair your wear down, as these can be easily caught and compromise your safety.

Final Tips

Final Tips:

  • Your car battery has a life expectancy of between 3 to 4 years. After this point, you should seriously consider a complete replacement.
  • Consider starting your car at least once a week to prolong its charge and prevent it from dying.
  • It’s essential to disconnect the negative terminal first and then the positive. This prevents a short circuit from developing in your car.
  • Check your driver’s manual for information on performing a battery diagnostic. Sometimes your dashboard may have a battery icon that tells you its condition.
  • Always clear dirt, debris, and corrosion from your car battery and spare. Any material between cables can compromise connectivity and lead to a failed charger.
  • Additionally, ensure no moisture gathers while the car hood is open. Strive to charge your battery in an open, dry, and cool area.
  • While it’s normal for tiny sparks to appear during a recharge, if sparks are consistent, large, and abrupt, it may indicate a problem with your car’s internal circuitry.
  • Always store your spare battery in a cool, dry place far away from liquid, excess heat, and pressure. A trunk can be more than ideal.
  • Always use compatible spare batteries to jumpstart your car. If in doubt, aim for a 12V power.
  • Use a high-quality battery charger to keep your spare in good condition. A poor charger can comproise the capacity of the battery, and lead to a quicker discharge.
  • Regularly turning on and driving your car will ensure its battery doesn’t lose charge. Going for even short distances can be helpful.
  • If your car and spar battery is failing and you are stuck for help, remember to check your insurance coverage for AAA roadside assistance.


Nothing feels worse than turning the keys in the ignition and your car’s engine doing nothing. And things can be all the worse if you’re in the middle of nowhere with no mechanic nearby.

Protect yourself from being stranded by keeping a spare battery in your car. As our article shows, using a spare battery is easy and straightforward, and once you adhere to safety precautions, it should be a stress-free task. You can expect a fully charged battery in your car without the help of a professional.

You need only a few pieces of equipment and adhere to safety precautions to boost your dead car battery back to life.

Because inactive batteries often discharge themselves, regularly recharge your spare battery so that it remains functional. This means checking it for corrosion, signs of leakage or damage, and performing a power check. Store it in a safe, secure, and dry place.

If you still have questions about jumpstarting a dead battery with a spare, please comment below.

But when in doubt, remember:

  • Your car battery will last between 3-4 years, depending on use. After that, it’s wise to replace it with a brand-new battery.
  • Your spare battery will only be of use if it is charged. Regularly inspect its power levels and keep it juiced.
  • Always disconnect the negative terminal first and then the positive. When reconnecting, perform the task in reverse order.

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