With smartphones, tablets, wireless earbuds, and even laptops becoming central to daily life, a power bank has moved from being a luxury to a necessity. For Indian consumers who travel, commute long hours, or face frequent power cuts, having a reliable power bank can make a big difference. But with so many options available in the market, choosing the right one requires some understanding of how they work and what specifications to look for.
The first factor to consider is capacity, measured in milliampere-hours (mAh). A power bank with 10,000 mAh capacity can usually charge a mid-range smartphone about two times, while a 20,000 mAh power bank can handle multiple charges or even power a tablet. However, the actual performance depends on conversion efficiency, which is never 100 percent. Heat loss and voltage conversion typically reduce efficiency to around 70–85 percent, so a 10,000 mAh power bank may deliver closer to 7,000–8,500 mAh to your device. For most users, 10,000–20,000 mAh offers a balance between portability and charging ability.
Next comes output power, which is where watts, volts, and amps become important. The power a charger or power bank delivers is calculated with the formula:
Watts (W) = Volts (V) × Amps (A)
For example, a power bank outputting 5V at 2A gives 10W, while one delivering 9V at 2A gives 18W. Modern smartphones support fast charging, which often requires higher voltage and current combinations such as 20V × 3A = 60W. If your phone supports 33W fast charging, a basic 10W power bank will charge it very slowly. On the other hand, if your device does not support high wattage, using a 65W power bank will not harm it, because devices usually regulate the maximum input they accept. What matters is ensuring the power bank supports the required protocol for your device.
Some brands use proprietary charging protocols that go beyond the universal USB Power Delivery (PD) or Qualcomm Quick Charge standards. For example, Oppo and Realme use VOOC/SuperVOOC, OnePlus uses Warp Charge, and Xiaomi has its own HyperCharge system. These protocols often deliver very high wattages at unusual voltage–ampere combinations, such as 10V × 6.5A = 65W. A normal USB PD power bank may fall back to basic 18W or 30W charging for these devices, which is slower but safe. The risk arises when users rely on third-party or poorly labeled power banks that claim “fast charging” without specifying which protocol they support. If the power bank does not communicate properly with the device, it may not deliver the expected speed, or in rare cases may cause overheating and long-term battery health issues, especially in budget devices that lack advanced protection circuits. This is why buyers should not only look at wattage but also check compatibility with the phone’s charging standard. If your phone supports USB PD, a PD-enabled power bank is the safest bet. But if your phone relies heavily on a proprietary protocol, it is best to use the original charger for the fastest speed, while using a reliable PD power bank as a backup option for safe charging at moderate speeds.
Safety and quality should not be overlooked. Reliable power banks use lithium-polymer or high-grade lithium-ion cells and come with built-in protections against overcharging, overheating, and short circuits. Cheaper, unbranded power banks may not provide these protections, increasing the risk of swelling batteries or even fire hazards. It is also essential to look for clear labeling. Manufacturers should mention the supported voltage and current levels along with the wattage, instead of only advertising “fast charging” in bold. Without this information, consumers cannot easily judge whether the power bank is truly suitable for their device.
The number and type of output ports are another important factor. Many modern power banks come with both USB-A and USB-C outputs, with the USB-C port usually supporting higher wattage and faster charging. If you plan to use the power bank for a laptop or tablet in addition to a phone, look for one that supports USB Power Delivery with at least 45W output. For multiple devices, check if the power bank can deliver high output on more than one port at the same time.
Portability also matters. A slim 10,000 mAh power bank is easier to carry in a pocket or handbag, while a 20,000 mAh model is bulkier but better for long trips. Airlines in India allow carrying power banks up to 27,000 mAh (100 Wh) in cabin baggage, so anything above that is not permitted on flights. Keeping within this limit ensures you can travel without issues.
When choosing cables, make sure they are rated properly for the power levels you need. A weak or uncertified cable may not handle 60W or 100W charging safely, even if your power bank supports it. Look for cables that clearly mention their wattage, volts, and amps, not just generic “fast charging” labels.
A reliable power bank is more than just a backup battery; it is a safeguard for your digital life. By checking capacity, supported wattage, voltage and current combinations, charging protocols, and safety features, you can make an informed choice. For Indian consumers, this means not only faster and safer charging but also better value for money. Investing in a quality power bank ensures that your devices remain powered when you need them the most, whether during travel, emergencies, or simply through the demands of a busy day.