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Lithium Battery lifetime calculation

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Yusra Osman

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I have a device that consumes at maximum 1.5 A. I want to use Galaxy S5 battery, which is 2800mAh capacity and 500mA output current. How would I calculate the time of operation using this Bat?
 

The calculation is mAh/I so in theory it would last 2800/1500 = 1.86 Hours but you would be loading it at three times it's rating so expect it to be shorter and damage or reduce the battery lifetime. Be careful if the battery overheats, Lithium batteries can ignite or explode if they get too hot.

Brian.
 

Thanks betwixt for reply. So I should use capacity info not output current? what's difference in case of Li BAT?
 

Capacity is a measure of stored power, current is a measure of how fast the store can be emptied. In general you should use the capacity figure but keep the current below the maximum rating.

Treat that battery as having 2800mAh capacity with a discharge time of 2800/500 = 5.6 hours at no more than 500mA load. You have to respect that no matter what the capacity is, there is another limit to consider. For example, you couldn't say a 2800mAh battery could produce 100 Amps for nearly 2 minutes because although the calculation works OK, the battery would melt!

Brian.
 

There are many companies making batteries for the Galaxy S5 smartphone. None of them say its maximum allowed output current.
It is Lithium and it is not protected so its maximum allowed continuous output might be 20A or more. I think your battery will be fine delivering only 1.5A.

I use 325mAh Lithium-Polymer model airplane batteries. Its maximum allowed continuous current is 70 x 0.325A= 22.75A and short duration bursts are allowed at double that!

BUT you must have a circuit to detect when the battery voltage has dropped to 3.2V then it turns off the load or the battery will be ruined and might explode or catch on fire the next time it is charged.
 

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