Pardon my ignorance but I just can seem to find an Answer to my question and I hope that you can help me.

What is the equation for calculating how long a Lithium Battery can supply a device?

For instance a Lithium battery has a capacity of 5600mAh, and an Output of 5V 2A. The drawing device requires 350mA and 5Vdc.

Is it as simple as dividing 350 into 5600 which would give me 16 hours of charge with optimal conditions? (This seems too easy.) or am I missing something?


Yes , that's easy because mAh is presented for a specific voltage that battery can output. Because the battery must output at a specified voltage. Your 5600mAh is for 5 volts. If it's not 5 volts. You must recalculate it. But the voltage shouldn't be change if the battery is not adjustable.

Hope you understand

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  • $\begingroup$ Although in a real battery the voltage will drop as it empties so you probably can't use every last mAh. How far you can empty it depends on the chemistry and design $\endgroup$ – Martin Beckett Apr 14 '14 at 19:39
  • $\begingroup$ @MartinBeckett Absolutuely right!! Thanks for adding information. $\endgroup$ – Poomrokc The 3years Apr 16 '14 at 1:08

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