The Battery Completely Dead, Can You Still Jump The Battery?


One of the tricks to start the engine with a dead battery is the jump start method.

But what if the battery is completely dead, it means that there is no voltage left in the battery. Can it still be?

What is Battery Jump Start

Battery jump start is a technique to start the engine, where the battery has no voltage.

The principle of the jump start is to use another power source for the starter system without removing the empty battery.

So all electrical systems in a car, including the starter system, have an energy source that comes from the battery. If the battery is dead, of course all electrical systems will die. However, if we switch it to another energy source, it is another battery which is fully charged, so the electrical system will run normally.

Jump start, can divert the energy source to another battery without removing the original battery.

The trick, by connecting the two batteries in parallel. This connection will supply a voltage from the jumper battery to the origin battery with the same value. So that the electrical system will get the same voltage source, that is 12 volts.

To do a battery jump start, you need a fully charged battery. It can be from other cars that have fully charged batteries. Then two jumper cables.

You only need to connect the two battery terminals with the same type, positive with positive, and ground with ground.

After that, you can start the car as usual and the engine will start.

When the engine is running, you can disconnect the jumper cables and the engine will stay run.

Returning to the topic, what if the battery is completely dead? Does the engine keep running when the battery jumper is disconnected?

Of course it is ok, because every engine has a charging system. The charging system functions to recharge the voltage on the battery.

But when the battery is completely dead, the voltage generated by the charging system will be prioritized for the engine's electrical system supply, such as the ignition system and the EFI system.

If there is more electricity from the charging system, it is used to recharge the battery. So that the battery will be full by itself.

But it's a different story if the electrolyte battery is low. This means that electrolytes cannot store electrical energy in a large amount. So in this condition, battery cannot be used for starting.

But it can still be turned on via a jump start as described above. If you disconnect, the engine keeps run because the electricity needs are supplied by the charging system. When the engine is turned off, the battery is unable to start the engine.

The reason is, the battery is already charged with electrical energy. However, because the electrolyte storage capacity is weak, only a small amount of electricity is stored in the battery. That is why the battery is not able to start.

To find out the condition of electrolytes, there are several ways

1. Measure the specific gravity

If you have a tool to measure the specific gravity of electrolytes, you can find out whether the electrolytes are in normal conditions or not.

2. CCA battery

In sealed lead acid type batteries, we cannot access electrolytes. It's because of the closed battery design. To check it, you can use a battery tester. You can measure the voltage, and the most important is the CCA.

Each battery has a CCA standard printed on the battery box. If the rated CCA is lower than the standard, the battery will need to be replaced.