By Erik Watkins

How Many Watts Are In A Car Battery: A Simple Calculation

Last Updated: June 30, 2022
How Many Watts Are In A Car Battery

If you are wondering how many watts are in a car battery, this article will help you. While manufacturers do not show this figure on their products, there is a way to work the numbers on your own.

Don’t rush. Go through the following information and instructions carefully to ensure you fully understand the terms and calculations.

How Many Watts Are In A Car Battery?

On average, a car battery comes with 12.6 volts and 105 amps, equaling 1323 watts.

What Does The Watt Number Means For A Car Battery?

Before getting to know the number of watts in a car battery, you need to understand two terms: car battery wattage and watt-hour. 

Watt is a power measuring unit that indicates how much power is in a device. It’s often used with electrical devices like machines, motors, or heaters. 

Meanwhile, a watt-hour is a unit used to measure a device’s energy usage. The number of watt-hours also illustrates the power capacity, meaning how many watts of power a device can deliver in an hour. 

Both watt and watt-hour have variants for measurement, such as megawatt, kilowatt, kilowatt-hour, megawatt-hour, etc. 

When discussing the power of a battery, watt-hour is the proper unit to use. 

How To Calculate A Car Battery’s Watt-Hours?

Manufacturers do not print a battery capacity on its case. However, they provide certain specifications that you can use to calculate the watt-hours in a car battery, including voltage (V) and ampere-hour (Ah).

  • Battery voltage: The electric potential difference between the battery’s positive and negative sides. The typical car battery has 12 volts, divided into six cells. 
  • Ampere-hour: This unit measures the battery charge that allows 1 ampere of current to flow in an hour. In another word, ampere-hour indicates the amount of energy a battery can supply for one hour. 

You can easily find these specifications on the battery case. To figure out the car battery watt-hours, rely on the following formula: 

Ampere-hour x Voltage = Watt-hours

For instance, the car battery in the following image features a voltage of 12V and an ampere-hour rate of 4Ah. The watt-hour rate of this battery is 4 x 12 = 48 watt-hours (Wh).

How To Calculate A Car Battery’s Watt-Hours

How Many Watts Are In A 12-Volt Battery?

To be exact, the average automotive battery has a voltage of 12.6 volts, consisting of six 6.1-volt cells. At the same time, the average ampere-hour rate is 105 amps. 

By calculation, the batter would have: 12.6 x 105 = 1,323 watt-hours.

It’s worth noting that while the 12V car battery voltage has become a common standard for automobiles, the ampere-hour rate varies a lot among brands and models. Therefore, it’s best to check out the specifications shown on the case. 

How Many Watts Does A Car Use?

The answer to this question depends on what battery is installed in your vehicle. The wattage is determined by not only the size of the battery but also the type of battery. 

To know how many watts a car uses, you also need to do some calculations based on the ampere-hour and voltage rate of your car battery. Then, using the same formula, you can determine how much electricity your car uses. 

When it comes to the type of battery, it can be said that lead-acid batteries are less efficient than lithium-ion batteries. That’s why a car with a lead-acid battery will use more power than one with a lithium-ion battery. 

How Many Watts Can A Car Battery Supply?

The number of watts a car battery supplies is not the same for every vehicle. As mentioned, a typical car is designed to have a 12-volt battery. However, the ampere-hour rate is different from one battery to another. 

For instance, with a 12V 100Ah battery, it’s translated into 1200 watt-hours of power. With this power capacity, the battery can produce 1200 watts in an hour, 600 watts in 2 hours, or 400 watts in 3 hours. 

It means there isn’t a definite number regarding how many watts a car battery can supply. 

On the other hand, a battery’s power supply is affected by external factors, such as the temperature. In the winter, it produces less power, which is why it takes longer to start your car than in the summer.

See more: How Many Amp Hours Is A Car Battery

How To Choose Car Battery

Technology

One of the first things to decide when shopping for a car battery is whether you want a deep cycle or an AGM battery, depending on your needs.

An AGM or a starter battery delivers a huge amount of power to help you start the engine. The alternator then recharges it. However, it cannot endure several discharge/recharge cycles, so improper use can reduce the battery life significantly. 

Meanwhile, a deep-cycle battery gives a steady amount of power over a period of time. Batteries using this technology don’t suffer from damages from repeated discharges and recharges. As a result, they are more durable. 

Power

When browsing car battery models, power is the next factor to remember. Here, you must check out the reserve capacity (RC) and cold cranking amps (CCA). 

CCA indicates the battery’s starting power, which must match your car’s requirements. RC shows how many minutes of reserve power is in the battery at a given load, which ensures all accessories in the car are powered. 

Maintenance

There are maintenance-free batteries and maintenance-required ones. The former cost a lot more, but you don’t have to worry about electrolyte monitoring. 

Though the other type is cheaper, you have to check the electrolyte level and top it up when needed. It calls for more effort and attention from you. 

Specifications (Amps per Hour and C20)

Amp-hour (C20) is an important specification to consider if you want to buy the best battery for your car. It illustrates the amount of energy stored to supply for 20 consecutive hours at 80 degrees F without dropping to under 10.5V. 

Related Questions

Can You Power A House With A Car Battery?

Yes, you can. However, you will need a power inverter to match the battery’s current with your house’s current. 

Can You Use A Car Battery As A Generator?

Yes, you absolutely can. Your car battery can act as a power bank for you to charge your devices. Yet, you need a power inverter made for 12V batteries.

How Many Watts Is A 12V 100Ah Battery?

To answer this question, you need to multiply the voltage by ampere-hours. You will get: 12 x 100 = 1200 watt-hours. A 12V 100Ah battery holds 1200 watt-hours of power.

How Many Watts Does A Car Battery Charger Use?

To charge a car battery, a 10A charger uses less than 200 watts, while a 25V charger would use less than 500 watts. 

Conclusion

Overall, the general formula is multiplying the volt by the ampere-hour to determine how many watts are in a car battery, how much electricity your car uses, or how much power it can supply. 

You should quickly find these specifications on the battery case and do the math within seconds. If you are looking to replace your car battery, it will help to know these figures in order to select the right model for your vehicle.

Automotive Master Mechanic at PowerAll

With 7 years experience in management positions leading automotive mechanics at PowerAll, Erik Watkins wishes to share useful knowledge and information about automotive mechanical equipment.

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