A Breakdown of How Many Amps to Start a Car

How many amps to start a car? Have you ever been curious about that? You may need to jumpstart the car or purchase a new battery and knowing the amp requirements is necessary for these things.

The Important Factors to Consider

There is no straight answer to the amp requirement for starting a vehicle. Several factors play into this, including the operating voltage and the state of the starter and wires. But the key factors are the engine size, type of oil used, and ambient temperature. A small engine may need only 50 amps for the initial boost, but a bigger engine will need more amps. Similarly, other factors also determine the number of amps.


The fuel used in the car or its viscosity, to be more precise, plays a role in determining the amps. For example, an engine using a 5W-15 oil will start more easily than the one using a 40W oil.

start a car engine
Oil and Temperature Affect the Way an Engine Starts. (Photo Source: picautos)


Ambient temperature actually affects the engine oil, not directly the battery amps. The oil becomes thicker in colder temperatures, resisting a free flow. For this reason, the battery draws a higher amount of current at lower temperatures.


How Many Amps to Start a Car?

Most small to midsize cars won’t need more than 400 amps. It’s likely to be enough for most compact SUVs and light trucks. Bigger vehicles will need more amperes, probably 1,000 amps. Remember that the amps required to kick off the engine are always lower than the cold cranking amps (CCA) of the battery.

Another thing to consider is that a high-amp jumper can kickstart a car that requires a lower amount of amps. For example, a 1,000 amp jumper will work for a vehicle that needs 500 amps to start. But it won’t be sufficient if the vehicle requires 1,300 amps.

If you buy a 400-amp unit, it won’t boost a car that needs 800 amps to start. But the car may not respond because of a dead battery. For example, you may have left your car radio or a light turned on overnight, which drains out the battery. In that case, a 400-amp unit can charge the battery, which can easily restart the engine.

Just connect the power unit to your battery and wait a few minutes to let it get recharged. Buying a high-amp power pack is the right decision, but a cheaper 400-amp pack is not bad either. You can use it 30+ times for effortless boosts of your vehicle.

how many amps to start a car
Even a Cheap Amp-Booster can Recharge a Battery Several Times. (Photo Source: shutterstock)

The Voltage Calculation

So, now you know how many amps to start a car, but the estimation is a little different for the voltage. If you have a 6V battery, don’t plug it into a 12V source or else it will blow up.

The starter motor’s power is calculated on wattage, which you get by multiplying volts by amps). For a 12V battery, the engine will require approximately 200 amps for starting off. But the figure will increase when the battery drops voltage.

So, the things to remember are that you can use a more powerful amp-pack but not a more powerful volt pack.