The lux (symbol lx) is the derivative unit of the International System of Units for the illuminance or lighting level. Equal to one lumen/m². It is used in photometry as a measure of luminance, taking into account the different wavelengths by the luminosity function, a standard model of the light sensitivity of the human eye.

Light meter (also called luxmeter or light meter) contains a photocell that captures and converts light into electrical impulses, which are interpreted and displayed on a display or needle with the corresponding scale of lux. It is used for precise measurement of luminous events in the field of industry, commerce, agriculture and research can also utilizarce to check lightingng the computer workstation in the window dressing and the world of design. The device has a central unit which displays a measurement range: 200, 2000, 20000 or 200000 LUX either 20, 200, 2000 or 20,000 FC. (Picture 1). In turn has a light sensor (picture 2)

When calculating the life of a battery it will be necessary to know the number of charge cycles that can be performed until the battery does not begin to lose its capacity.
Depending on the type of battery these charging cycles can vary, the most common being the mobile batteries, manufactured Li-Ion or Li-Po, which have a duration of between 300 and 500 charging cycles according to model and manufacturer.
Once thisE limit we will notice how the battery loses duration of operation, arriving to lose up to 25% of its capacity of load.
At this point it will be necessary to evaluate a battery change.
It should be noted that usage and charging habits can significantly affect battery life. For example, factors such as heat, charge the battery several times a day without it is almost exhausted, etc. Will be affectedits duration.
Therefore, to get the most out of the battery we must know when a full charge cycle is performed, and try to avoid misuse of charge, to increase its useful life.
A charging cycle is considered when the battery has been discharged or its 100% charge has been used.
The manufacturers advise that the charge is never made below the 58% battery, since the battery voltage would not fall so lowTo, so you could end up winning up to 4000 charge cycles.
Tips to increase the life of a battery.

• Avoid extreme heat or cold or very long applications of the device.
• Charge the battery as often as you can.
• Fully discharge the battery from time to time.
• Do not let the battery run out completely before charging.

Below is a table with theDifferent voltages (V), charge cycles (C) and battery percentage (B).