# Calculating total energy of battery (J)

• mburt
In summary, the conversation discusses calculating the total electric potential energy of a battery with two cells and determining the duration of a motor running on a certain combination of batteries. The conversation also mentions the watt hour rating of a battery and Peukert's law. The final point is about the efficiency of a battery and whether a lower watt bulb would make it last longer. Further research is needed to fully understand the calculations involved.
mburt
Hi. How would you calculate the total electric potential energy of a battery containing two cells (just an example), with for instance 20 V (cumulative, if cells are in series) and runs on a 60 A circuit.

Is it required to have the charge of the battery to calculate total energy in joules?

The whole point of this is to calculate how long a 100 W motor would run on a certain combination of batteries.

(By the way, these are all hypothetical situations)

Thanks

One measure is the watt hour rating of the battery. This is voltage times current times the number of hours it can provide that.

So an approximate answer is provided by the product of the rated voltage of the battery times the amp hour rating...

http://en.wikipedia.org/wiki/Automotive_battery#Terms_and_ratings

If you want to understand more, also check Peukert's law.

In practice A battery actually disppates energy (during charge and discharge) via its own internal resistance...hence a wet cell lead acid battery with a higher internal resistance is not actually as efficient as a low resistance AGM battery

Oh okay thanks. But wouldn't a batter last longer running a 50 W bulb compared to a 75 W bulb?

I assumed that if you knew the total number of joules of energy that a battery could produce, then you could calculate the total time it would take to discharge.

Hm I guess it's a little more complicated then that, I'll have to do some research

## 1. How is the total energy of a battery calculated?

The total energy of a battery is calculated by multiplying the voltage (in volts) by the charge capacity (in ampere-hours).

## 2. What is the unit of measurement for total energy of a battery?

The unit of measurement for total energy of a battery is joules (J).

## 3. Why is it important to calculate the total energy of a battery?

Calculating the total energy of a battery allows us to determine how much energy the battery can provide and how long it can power a device. This is important for managing battery usage and determining when a battery needs to be replaced.

## 4. Are there any other factors that affect the total energy of a battery?

Yes, the temperature and age of a battery can also affect its total energy. Higher temperatures can decrease the total energy output, while older batteries may have a reduced charge capacity and therefore a lower total energy.

## 5. Can the total energy of a battery be increased?

No, the total energy of a battery cannot be increased. However, it is possible to increase the charge capacity of a battery by using larger or more efficient cells, which can indirectly increase the total energy output.

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