Have you ever wondered how many amps are actually needed to start a car? When you look at a car battery it has a CCA rating. That is the Cold Cranking Amps. When you start a car engine it can draw enough current to drop the battery voltage to 6V. That is the CCA rating of the battery. The electronics are designed to work enough at 6V to get the engine started.
As soon as you stop cranking the voltage will jump back to 12V and everything will be working. The current required depends on engine design, engine/oil temperature. If the engine is cold it is routine to draw 100–200A. Most small-sized vehicles will take 200-250 amps to start a car if the engine is cold. In the case of trucks, more than 400 amps are necessary.
The ECU will decide whether to crank the engine or not, so if your battery voltage is below about 10.4V then many cars will not even try to start. The alternator can charge your battery at 100A, so if you crank at 200A for 5 seconds to start, then it can be recharged in about 10 seconds. If your battery is dead and is not giving any output, you can try this method here.
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