Suggest a good battery pack for smartphones

I use an Android handset with a dual-core processor. My problem is that its battery barely lasts 8 hours. I have heard of battery cases for phones. Can you suggest a good brand? Also, suggest a good externalbattery pack for smartphones 

—-Rohan Sharma, Prashant Patil

We have seen such cases available for the iPhones and certain Android smartphones such as the Samsung Galaxy S III, but are not aware of their availability in the Indian market. You can, however, pick up an external power bank. These are battery packs that comprise either lithium-ion or lithium-polymer cells that can be charged to store power - and later, when your phone runs out of juice, you can simply connect these via USB to charge your device. When buying... Buy a battery pack that uses lithium polymer cells.

These provide double the charge density per unit weight when compared to lithium-ion . On the other hand, lithium-ion technology is the cheaper of the two technologies. Most USB devices draw not more than 1 Ampere to charge their internal batteries. However, some smartphones and tablets need 2.1 Ampere current. So check your device's charging requirements before buying a battery pack. Most battery packs do not offer more than 75% efficiency.

So it's always better to invest in a higher capacity battery pack than what you require. Buy a 5600mAh if you need 4000mAh. The CoolerMaster PowerFort ( 4,999) uses a 6,600mAh lithium polymer battery that allows for the simultaneous charging of two devices. Its 5V-1 A connector is ideal for charging most phones, while its 5V-2 .1A port charges tablets and bigger handsets. Then there's the Zebronics Power Grid ( 1,990) that uses a 4,800mAh lithium-ion battery, but also comes with a 5V-1 A as well as a 5V-2.1 A connector to charge two devices simultaneously.

If your need is only for a 1A charger, then you could opt for either the 2,200mAh Nokia Universal Portable USB Charger DC-16 or the 2,600mAh PM Powerpack 'Recharge+' Power Bank. Both these retail at 1,499.