What are watt-hours on a battery- introduction and calculation?

Any person who uses batteries needs to know how long your battery will provide power. It is most important when it comes to people who own cars. Calculating how long your battery will last before it needs to be recharged will save you from suffering a dead battery in the middle of anywhere. To prevent this, you have to know the total number of watt-hours your vehicle uses.

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A watt is the standard unit of energy which can be defined as joule per second. It is the amount of energy consumed by a device. It shows how powerful a device is. Before buying a battery for any device it’s important to check the watt hours. The general rule of thumb is that the more the watt hours the battery has the longer it will last. If you have a 200watt hour battery it means that it will release exactly 200 watts in one hour before it is discharges at a specific voltage. 

Below we discuss what watt-hours on a battery is. We also discuss how you can calculate watt-hours and how long watt-hours last. Let's get started.

How to Calculate Watt-Hours of a Battery

A watt-hour is a unit of energy denoted as Wh. It measures the capacity of power in watts moving over time (an hour). To better understand it, compare it to battery life. When talking about battery life, it means the number of watts that an application or device uses per hour.

So, if your device is rated at 100W, it will use 100W of power in an hour and 200-watt hours in two hours

To calculate watt-hours from amp hours, you will use the following formula:

Watt-hours = Amp-hours * Volts

Where; voltage is the amount of energy that is given to an electronic circuit.

Amp-hours is the capacity of the battery. It can also be defined as a measurement of current in amps flowing over a period. It is the number of amps a device or an application draws when you u it for an hour.

For example:

A battery has a voltage of 11.1 and a capacity of 4400 mAh. Calculate the watt-hours.

In the example above, you will first need to get the Amp-hour rating. To get this, divide the mAh rating by 1000. 

4400/1000 = 4.4ah

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To get the watt-hours, you will use the formula above. 4.4 Ah x 11.1 volts = 48.8Wh

Example 2

Suppose you have a car battery that runs on 12 volts and is rated at 100Ah. To get the watt-hours, you will need to multiply the volts by the amp hours: 100Ah x 12 volts = 1200Wh. This will mean the battery has a capacity of 1200Wh.

Note:

Watt-hours are different from Amp-hours. The Amp-hours will vary slightly depending on the nominal voltage. For instance, a 12-volt battery with 50Ah will have an average pf 650Wh, while a 12 V battery with 100Ah, will have 1300 Wh.

How many watts in a 12-volt battery?

A 12 Volt battery usually has six cells that produce 12.6 volts of electricity when the battery is fully charged. However, this will decrease as the battery is continuously discharged. Therefore, it is good to know your battery's watts and watt-hours.

When calculating watt-hour, we will use the formula according to Ohm's law.

Watt-hour (power) = battery voltage x Amp hour 

For instance, a 12 volts 50 Ah battery calculation will be 50 Ah x 12 volts = 600Wh. 

If the battery amp hour is 1Ah, the watt-hour will be = 12 V x 1 Ah = 12Wh if the battery amp hour is 300, Ah, Watt Hour = 12V x 300 Ah = 3600 Wh.

If your battery energy capacity is 12 volts and has a capacity of 60Ah, it will have 12 x 60 = 720-watt hours.  

Therefore, when you want to know the number of watt-hours in your 12-volt battery, it is good to know the amp hours first. A 12-volt battery with 105 Ah can supply 1260 watt-hours or 1.26 kWh under perfect conditions and 100% discharge.

Example

Suppose you have a car that is running in gear speed setting 2. The engine runs on 12 volts and draws15 amps. The car will have a power consumption of 180W (12 X 15). When you switch to a speed setting of 4 that draws 25 amps and still runs on 12 volts, the car's power consumption will be 300W.

How long does a watt-hour last?

One watt-hour is defined as 1 watt of power expended for 1 hour. One-watt hour equals one watt of the average power for over one hour. Therefore 1 watt will last for one hour. 

Example 1: 

A 100 watt light bulb is supposed to last for 4 hours. Therefore, the watt-hours of the battery will be 100 x 4 = 400-watt hours.

Example 2:

A regular car battery with a 12-volt rating usually has a 48 Ah capacity. The battery can provide around one amp for two days straight with a complete charge cycle. It can also deliver around two amps for one single day. Apart from this, the battery will have 576-watt hours (12 x 48)

Conclusion

It is easier to calculate your battery's watt-hour once you already know the voltage and amps. Knowing your battery's watt hours and wattage, it becomes easier for you to travel or even prepare beforehand specific setups should your battery fail. Apart from this, knowing the watt-hours of your batter is crucial as it will help you buy the right battery and know how best to use it.

Therefore, the next time you buy a battery, take a look at the battery pack package or the battery itself. To get an idea of how many volts the battery has. You should also consider other factors like getting the right-sized battery with the correct cell power and reserve capacity when looking for a battery.

I hope you find this information useful when selecting the battery that fits your specific needs.