# Thread: Check if a battery consumption article is right.

1. ## Check if a battery consumption article is right.

Hello. I've a question risen from this article in the internet, it's about battery energy consumption. My calculation of how long the battery's charge last, from the alarm example in the article, doesn't add up with the one in the article. You don't need to read the article, just with the lines below I think you'll able to answer my question.
With the battery specs of the CR2450 found in here the energy held in the battery is 1.81 Joules, and with the energy consumption from the example in the table 4 that is 2.55 mJ, it would give 583 working hours that is just 24 days, but in the article says that it last for 4.33 years, am I right? what am I missing?

Thank you very much for your help.

2. Hi Rinaldi,

Without reading the article, I suspect they are referring to the life-cycle of the battery. Rechargeable batteries generally have a finite number of charge/discharge cycles before they begin to lose storage-reliability and able to maintain voltage levels.

3. HI PinkertonD thank you for your reply. The article talk about choosing the right battery for your embedded application and how to manage long duty cycles at low power consumption at micro Ampere scale generally in sleep mode with periodic picks to transmit data. So the time refers the battery discharging just once.

4. The difference between our calculations is due to the fact that in the article and many other sources doesn't take into account the voltage required to power the device, I mean they do care about power the circuit with the appropriate voltage in the appropriate time using a dc/dc converter and specially in the article that I mentioned above talk about it, but when the battery life is calculated it all comes down to the average current consumption within an hour, making:

battery life(h) = (Battery capacity Ah) / (Current consumption Ah)

and I was calculating:

battery life(h) = (Battery energy in Joules) / (Device consumption in Joules per hour)

Battery energy = Battery's nominal voltage * capacity

Device consumption = Battery's nominal voltage * drawing current * time spend within an hour

The device's total energy consumption would be a sum of it's different states.

Do you know why calculating through the actual energy consumption gives me the wrong battery's life expectancy?

5. Yeah, rechargeable batteries differs from its energy consumption It think.. Rinaldi has an idea..

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