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

The battery bank or Power Bank is an ideal solution if you are running out of battery on your device when you really need it.
It's charged using a miniUSB or microUSB cable directly connected to a power source or USB port (PC or MAC).

Its operation is very simple, you only need to connect the battery bank to your smartphone, tablet, MP3, Ipod, etc. and automatically will start charging.

The provided charge to the device depends on the capacity in mAh of the battery bank, usually can perform a full charge of a device and depending on the capacity of the power bank, it can do it a few times.

To calculate the times you can charge your device simply divide the capacity of powerbank between the battery capacity of the device.

Example:
If the battery bank is 7.200mAh i your device is an Apple iPhone, Samsung Galaxy or similar with 1.800mA battery, you can charge up to 4 times without going through the plug.

The charging time of your device using a powerbank is very similar to the charging time using the original charger.

Ideal for long trips, meetings, campsites, etc.

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).