Best Portable Chargers (2025): iPhone, iPad, Laptops & More

Many years ago, the Samsung Galaxy Note 7 gained infamy when its batteries caught fire in a series of incidents. Since then, there has been a steady stream of similar, albeit isolated, incidents. However, despite the widespread coverage of damaged batteries, the vast majority of lithium-ion batteries are safe.

The chemical reaction that takes place in a lithium-ion cell is complex, but as in any battery, there is a negative and a positive electrode. In lithium batteries, the negative is a lithium-carbon compound and the positive is cobalt oxide (although many battery manufacturers are moving away from cobalt). These two compounds cause a reaction that is safe to control and supply power to your devices. However, when the response gets out of hand, you end up with headphones that melt in your ears. What changes a safe response to an uncontrolled response can be many things: excess heat, physical damage during use, physical damage during manufacturing, or using the wrong charger.

The three main rules that have kept me safe (so far) through testing dozens and dozens of batteries are:

1. Avoid cheap cables, chargers and plug adapters.
2. Make sure the batteries are not exposed to excessive heat (above 110 degrees Fahrenheit).
3. Check batteries regularly for signs of damage.

Avoiding cheap adapters, cables and chargers is the most important thing. These are your most likely source of problems. Those chargers you see on Amazon for $20 less than the competition? It’s not worth it. They probably kept the price down by skimping on insulation, abandoning power management tools, and ignoring the basics of electrical safety. Price alone is no guarantee of safety either. Buy from reputable companies and brands.

Then there is heat. Too much of it can cause all sorts of problems, both disposal-wise and safety-wise. Avoid heat and pay attention to your batteries when they are charging. If your device gets too hot while charging, it could be a sign of problems. Likewise, beware of any swollen, bulging, or otherwise deformed batteries.