How to understand a battery specification [duplicate]

Question

I read a data sheet of a li-ion battery to use it in my project. In the data sheet, it is mentioned that c5mah= 2200mah. I couldn't understand what that means. Please help me with understanding that.

Answer 1

In the data sheet, it is mentioned that c5mah= 2200mah. I couldn't understand what that means. Please help me with understanding that.

"c5mah" (sometimes written as C5mAh or C₅mAh) means the capacity (in mAh) which a battery has, when discharged at the 5h rate i.e. the rate which fully discharges the battery in 5 hours, from a specified fully charged state, down to a specified fully discharged state (e.g. perhaps down to 2.75V for a Li-Ion cell, but check your specific datasheet).

In your specific case, the discharge current for the C5 rate is calculated as:

$$\textrm{2200mAh / 5h = 440mA}$$

So discharging a fully charged 2200mAh battery of that type, using a constant current of 440mA, would discharge the battery (down to their specified end condition - see the datasheet for details) in 5 hours. That's it.

You can think of C5 as being a tighter definition (more constrained specification) of "C", the battery capacity, as it gives a specific test condition i.e. the discharge current. Note that a battery's C2 (or C1) capacity value will be less than its C5 capacity value. Whereas its C10 or C20 capacity value will be more than its C5 capacity value.

Other test conditions will also be specified, as they affect battery capacity too e.g. temperature, end voltage (i.e. fully discharged voltage) etc. That is why there isn't a fixed value for "C" which applies under all test conditions.

(As others have said, in future, please supply a link to, or relevant screen captures from, any datasheet that you ask questions about.)

Answer 2

mAh stands for miliampere hours, which is the total product of delivered current and time, which for this battery equals 2200. So in this case, if your circuit draws 2.2A (2200mA), the battery will last for one hour. If it only draws 1mA, the battery will last for 2200 hours. However, that's a rough simplification and ignores the impact of the discharge rate of your battery.

The discharge rate specifies the actual battery charge depending on the discharge current.

The higher your discharge current, the smaller is the actually capacity of your battery.

_{(source: insideevs.com)}

So usually the capacity on the battery is specified for 1C current, increasing with lower discharge currents and decreasing with higher discharge currents.