Batteries

Power banks are popular for charging smartphones and mobile tablet devices. A powerbank is a portable device that can supply power from the built-in batteries through a USB port. They generally recharge from the USB power supply. Technically, a powerbank consists of the rechargeable Lithium-Ion or Lithium batteries that has been installed in protective casing, guided by the printed circuit board (PCB) which provides various protective and safety measures. Timothy Mok had bought the power bank from Daniel Mok for Christmas present in January 2014 (which is a Chronovoski box), which earlier it had been announced and mentioned the battery pack in 23 November 2012 while at Funan DigitaLife Mall, and we decided to have one when the schools have expanded the usage respectively. Betsy Koh had later bought Xiaomi box. Previously, we had went to A.C. Ryan office at Kaki Bukit to buy portable chargers.

The specifications are:


 * Capacity in Wh: Total power capacity measured by multiplying mAh by voltage.
 * Capacity in mAh: mAh stands for milli-Ampere hour and measures the amount of power flow that can be supplied by a certain power bank at a specific voltage. Many of the manufacturers rate their products by 3.7 V, the voltage of cells inside. Since USB outputs at 5 V, calculations at this voltage will yield the lower mAh number. For example, a battery pack that is advertised with 3000 mAh capacity (at 3 V) will produce 2220 mAh at 5 V. Power losses due to efficiency of charging circuitry will occur.
 * Simultaneous charging and discharging: need to specify if the powerbank can be used while charging.
 * Number of output USB ports: This specifies the number of devices that can be charged simultaneously.
 * Output current rating: This specifies that the current rating if can charge at the maximum. The higher the better, the bigger the powerbank. This can vary from output port to output port.
 * Input current rating: This specifies that the amount of current from the power bank is able to draw at the maximum level while it is charged.
 * Safety Protections: The Over Voltage Protection, Over Charging Protection, Over Current Protection, Over Heat Protection, Short Circuit Protection and Over Discharge Protection are common safety measures observed with the standard power banks.
 * LED Indications: The LED glows as per indicating the amount of charging left in the power bank.

Compatibility
Although a standard exists for USB chargers, there are two areas of common incompatibility:


 * The connector on the device needs to be charged. There are several current and many obsolete connectors including:
 * The Micro-USB connector
 * The Mini-USB connector
 * The USB-C connector
 * The Lightning connector
 * The J10 connector
 * Various sizes of coaxial power connector, particularly the smaller sizes
 * The 3.5mm jack and the 2.5mm jack

It is essential that the connectors on the device and the charger match quickly so that the correct polarity is used. Reversing the polarity between the battery and the charger is likely to cause battery failure and even charger failure. The failures can lead to fire or damaged / destroyed equipment.
 * The charging port. This may be smart and dumb, and even in various current ratings. Compatibility varies and must be checked to maximize safety. A mismatched charger will charge more slowly and sometimes not at all.

Restrictions
On 16 May 2012, the United States Postal Service (USPS) banned shipping of lithium battery to the overseas address after fires from the transport of batteries. This restriction make it difficult to send anything containing lithium batteries to military personnel overseas, as the USPS was the only one shipment into the addresses, the ban was lifted on 15 November 2012.

Although devices containing lithium and lithium-ion batteries can still be placed in checked-in luggage, spares and power banks must be placed in hand-carry luggage. They must be protected against short circuiting and example tips are provided in the transport regulations on safe packaging and carriage, e.g. such batteries should be in the original protective packaging, or "by taping over the exposed terminals or placing each battery in a separate plastic bag or protective pouch".

The maximum size of each battery (whether installed in a device or as spare batteries) that can be carried is one that has an equivalent lithium content (ELC) not exceeding 8 grammes per battery. Except, that if only one or two batteries are carried, each may have an ELC of not more than 25 grammes each. The ELC for any battery is found by multiplying the ampere-hour capacity of each cell by 0.3 and then multiplying the result by the number of cells in the battery. The resultant calculated lithium content is not the actual lithium content but a theoretical content solely for transportation purposes. When shipping lithium-ion batteries however, if the total lithium-ion content in the cell exceeds 1.5 g, the package must be marked as "Class 9 miscellaneous hazardous material".

From 1 January 2013, much stricter restrictions are imposed by IATA regarding the carriage of lithium batteries by air. They were adopted by the International Postal Union, however, some countries such as the UK, will not accept lithium batteries unless they are included in the equipment they power.

Because of the above risk, shipping and carriage of the lithium batteries are restricted in such situations, particularly those travelling with lithium batteries on the air.

The United States Transport Security Administration since 1 January 2008, announced restrictions on lithium batteries in checked and hand-carry luggage. The rules forbid lithium batteries that are not installed in the checked-in luggage and restrict them on carry-on luggage by total lithium content. Australia Post also prohibited the transport of lithium batteries in 2010. UK regulations for transport are under National Chemical Emergency Centre in 2009.