How to charge a dead battery (with pictures)

How to charge a dead battery (with pictures)
How to charge a dead battery (with pictures)

Battery failures have many explanations: car immobilized for too long without starting, headlights left on, cold or quite simply a dead battery that no longer holds a charge. To recharge the battery, you are going to need jumper cables and a vehicle with a working battery. The battery in good condition will then charge your battery, at least enough to be able to start. It is then sufficient to connect the two batteries with the cables, the one in good condition recharging the flat one.


Part 1 of 2: What to do before wiring

Charge a Dead Car Battery Step 1

Step 1. Take a look at your battery

It must not show any cracks or cracks, or leaks of any kind.

If you spot such signs, do not charge or try to start the car with cables, you risk a serious accident. The battery must be changed

Charge a Dead Car Battery Step 2

Step 2. Wear eye protection and rubber gloves before handling the battery

These protections are useful in the event of acid projection.

Step 3. Next, check the condition of the cables coming to the battery

They must be well fixed and intact (sheath intact, terminals not corroded).

If there is corrosion (white or green powder) around the battery terminals and terminals, it should be removed with a rag or an old toothbrush

Step 4. Position the emergency vehicle (with the correct battery) facing the disabled vehicle

Position the vehicles so that the batteries are close to each other, but they should not touch each other. Either put the two vehicles face to face, or you place them in parallel by putting the batteries as close as possible to each other. It all depends on the position of the batteries in each vehicle.

  • Important point, but you will quickly realize: the distance between the two batteries must be less than the length of your cables. There are cables of different lengths on the market.
  • Do not connect never your cables if any of them are too short. You risk starting a fire, because a cable that is too short can melt.

Step 5. Turn off the engine of the emergency car

Part 2 of 2: wire the two batteries together

Step 1. Lift the two covers

Charge a Dead Car Battery Step 7

Step 2. Locate the positive and negative terminal of the battery

The positive terminal usually has a plus sign (+) and is usually connected to a red wire. The negative terminal has a minus sign (-) and is usually connected to a black cable.

Charge a Dead Car Battery Step 8

Step 3. Connect the cables

The red (positive) jumper cable must be connected to the two positive terminals of both batteries. Sometimes, on the red clamps, we see the sign "+". Proceed as follows: you attach one of the red clamps to the “+” terminal of the dead battery and the other red clamp to the same positive terminal of the good battery.

Step 4. Then connect one of the black clamps to the negative terminal of the correct battery

The negative cable is black. Sometimes, on the black pliers, we see the sign "-".

Step 5. Secure your connection

The other black clamp must be securely attached to a metal mass of the broken down car. This is called a "grounding". Most often, this clamp is attached to the metal frame of the car. Find a bare metal part, not painted or oxidized.

Step 6. Start the car in good condition

Thus, thanks to the alternator of this vehicle, the current generated will come, via the cables, to recharge the broken battery.

Step 7. Wait about 5 minutes, the time to charge the dead battery to a minimum

To fully charge it, it will take much longer. Here, we just want to restart the car.

Charge a Dead Car Battery Step 13

Step 8. Make a first attempt to start the broken down car

If your battery is not too old and holds a charge well, your car should start without a problem.

If it doesn't start, try recharging it for another 5 minutes

Step 9. Then disconnect the cables in the reverse order of connection

This will prevent sparks or even an explosion.

Disconnect the earth (1), then the black clamp on the back-up battery (2), then the red clamp on the back-up battery (3) and finally, the red clamp on the recharged battery

Charge a Dead Car Battery Step 15

Step 10. Let the rescued car run for about 5 minutes

The alternator then takes over and will, if there are no other problems, continue to recharge the battery.

Step 11. If you want a fully charged battery, ride for about 20 minutes or let it idle for the same time

If after a few hours or a few days, your battery is flat again, it is because it is "dead", it must be replaced, it no longer holds a charge.


  • In some auto stores or garages, your battery can be tested.
  • If your battery has removable caps (on top), remove them to check the electrolyte level in the compartments. Warning ! it's acid! You can, on this kind of batteries, top up the levels with acid.
  • By using thicker cables, the charge is accelerated. Ask the seller for advice.
  • Be careful when idling your engine after recharging. There is a possible risk of overheating.
  • On some cars, there may be variations in current. To avoid any problems, turn on the heating at maximum power and activate the defrost. If there is too much variation, the fuse will blow and the heater will absorb the excess energy.


  • As soon as the cables are connected, even partially, they must absolutely not come into contact, either directly or through a metallic object (a key which would accidentally fall on the two cables). You simply risk creating a short circuit, sparks and ultimately a fire.
  • When recharging the battery, hydrogen is released which is explosive. So be careful!
  • If you have a manual transmission, use the clutch pedal with care.

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