Power Bank Safety: What to Look For and What to Avoid
A 20,000mAh power bank holds roughly the energy of fifteen phone batteries in one hand-sized object. Handled properly this is unremarkable. The failures that make the news almost always trace back to the same few causes, and most are visible before you buy.
What to check before buying
Four things on the listing
- BIS certification. Power banks sold in India require it. A listing that shows a registration number has been through a testing regime; one that avoids the subject has not.
- Stated watt-hours. Required for air travel and a sign that the maker has measured the pack rather than printed a round number.
- Listed protections. Over-charge, over-discharge, over-current, short-circuit and temperature protection should be named individually.
- A brand with an address. If something goes wrong, a recall or replacement needs someone to be responsible.
The warning signs
Capacity that defies physics. Lithium cells have a known energy density. A pack claiming 50,000mAh in a pocket-sized body weighing 200g is claiming something no cell chemistry currently delivers. Roughly 350–400g for a genuine 20,000mAh pack is the benchmark; anything far lighter for a far larger claim is not what it says.
A price far below the category. Cells are the dominant cost. A pack at a third of the going rate has either fewer cells than claimed or cells that failed someone else's quality control.
No brand, or a brand that exists only on one marketplace. There is nobody to issue a recall.
Rattling. Cells should be fixed in place. Movement inside means they can be damaged by an ordinary drop.
Using one safely
- Do not charge it under a pillow or in bed. Cells need somewhere for heat to go. This is the most common preventable cause of incidents.
- Keep it out of the car. A dashboard in an Indian summer reaches temperatures well beyond any pack's design range, and repeated heat exposure damages cells permanently even when nothing dramatic happens.
- Use a cable rated for the current. A thin cable carrying high current gets hot along its length.
- Do not run it to zero repeatedly. Deep discharge is hard on lithium cells. Topping up is better for the pack than emptying it.
- Charge it where you can see it, at least the first few times with a new pack.
When to stop using one
These are not "keep an eye on it" signs. They mean stop:
- Any swelling. A casing that no longer sits flat, a seam opening, or a pack that rocks when placed on a table. Swelling means gas generation inside a cell and it does not reverse.
- Heat beyond warm. Warm during fast charging is normal. Too hot to hold comfortably is not.
- Any smell, particularly sweet or chemical.
- Physical damage after a hard drop, even if it still works — internal damage is invisible.
A swollen pack should not go in household waste and should not be punctured. Take it to an e-waste collection point; most Indian cities have them, and several large retailers accept batteries for recycling.
Flying with one
- Cabin baggage only. Never in checked luggage — this is a firm rule everywhere, because a fire in the hold cannot be reached.
- Under 100Wh is generally allowed without approval; 100–160Wh usually needs airline permission; above 160Wh is normally refused.
- Keep terminals from touching keys or coins — in the original box or a pouch.
- Rules differ by airline and change. Check yours before travelling.
For how the printed capacity relates to what you actually get, see why a 20,000mAh power bank never gives you 20,000mAh.