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)

Within the wide range of batteries on the market we can differentiate two large groups, disposable batteries and rechargeable batteries.
Disposable batteries are those that only allow a single use and when they are exhausted they can not be recharged. These batteries can store their energy for years.

Rechargeable batteries are those that can be recharged once exhausted. This type is losing charge when they are storedaccording to voltage. The most common we can find them of 1.2V and 3.7V

As a last point you have to take into account that lithium batteries, Lipo, Life etc. Due to its composition, specific loaders should be used.