The lumen (symbol: lm) is the unit of the International System of Units to measure the luminous flux, a measure of the light power emitted by the source. The luminous flux of radiant flux difference that the former provides the variable sensitivity of the eye to different wavelengths of light and the latter involves all electromagnetic radiation emitted by the source according Wien law and Stefan-Boltzmann regardless of whether such radiation is visible or not. 1 lm = 1 cd. sr = 1 lx. m2

Photovoltaic energy is produced by solar radiation using devices called photovoltaic cells. It is ideal for supplying all kinds of isolated houses, shelters, but also can be used to supply electricity on a large scale. We show the operating principle "In a semiconductor exposed to light, a photon of energy starts an electron, creating both a" gap "in the atom excitador. Normally, the electron quickly finds another hole to refill it, and the energy provided by the photon thus dissipates as heat. The principle of a photovoltaic cell is to force the electrons and holes to move towards the opposite side of the material rather than simply recombine in it: thus, there will be a potential difference and thus tension between the two sides of the material,as in a stack "The first ground application of a commercial installation of photovoltaic cell was developed in Japan in 1966. In the picture: 1 - PV Modules 2 - Regulation and Control 3 - Battery 4 - Inverter to power.... 220V

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).