It is normally used dBm optical fiber, external radio networks, microwave. This measure, which also can be called dBmW is a measure that is in decibels relative to one milliwatt. The main idea is to measure dBm power factors.

The dBm (sometimes also dBmW or decibel-milliwatt) is a unit of measurement of power expressed in decibels (dB) relative to one milliwatt (mW). It is used in radio networks, microwave and optical fiber as a convenient measure of absolute power because of their ability to express both very large and very small values ??in short form. It is distinct from dBW, which refers to one watt (mW 1,000). Typical values:

• 21 DBM-> 125 MW> Maximum output power for a mobile phone UMTS/3G (phone power class 4).
• 15 DBM-> 32 MW> Typical power transmission WiFi laptops.
• 0 DBM-> 1.0 mW = 1000 ?W-> Standard Bluetooth Class 3 coverage 1m.
• DBM- -10> 100 ?W-> Typically the maximum Potentiometeria that can be received on a wireless network (-10 to -30 dBm).
• -194 DBM-> 0.00004 AW-> thermal noise bandwidth of 1 Hz in outer space (4 kelvin).

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).

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.