As we celebrate International Battery Day on February 18th, 2025, it's crucial to understand the technology that powers our modern world. Batteries have become integral to our daily lives, from powering our smartphones and laptops to enabling the transition to renewable energy and electric vehicles. However, despite their ubiquity, many misconceptions persist about how batteries work and how to maintain them properly.

This article will explore and debunk some of the most common battery myths, helping you make informed decisions about battery usage and care. Understanding these facts will not only help extend the life of your batteries and devices but also contribute to safer and more sustainable battery consumption.

Your Battery Needs to be Empty Before Recharging

False

The idea that batteries incorporated in devices need to be fully drained before charging is a common misconception rooted in older technology. While this was true for older nickel-centric batteries that suffered from the "memory effect," modern lithium-ion and lithium-polymer batteries used in smartphones and other devices work differently. In fact, completely draining these newer batteries could potentially cause more harm to them.

For optimal battery life, keeping your device's charge level between approximately 20% and 80% is recommended. This range minimises stress on the battery's internal chemistry, where lithium ions move between lithium cobalt oxide and graphite layers. At 50% charge, these layers are in perfect equilibrium, creating ideal conditions for battery longevity. However, this is not something to worry about too much. While it is true that rechargeable batteries gradually lose capacity over time, this loss is minimal. Most modern smartphone batteries maintain about 80% of their original capacity even after years of regular use. If capacity eventually does become an issue, battery replacement is a straightforward solution to restore full performance.

Keeping Batteries in the Refrigerator or Freezer Makes Them Last Longer

False

Many believe that keeping batteries in the fridge or freezer will extend their lifespan, but this is a persistent myth. While excessive heat can damage batteries, extreme cold isn't beneficial either—in fact, it can do more harm than good. Storing rechargeable batteries like NiMH or lithium-ion in freezing temperatures can slow their chemical reactions, reducing efficiency and potential long-term damage. Meanwhile, alkaline batteries are particularly vulnerable to condensation when moving between cold and warm environments, which can cause corrosion and degrade performance. The ideal battery storage solution is a cool, dry place—not freezing cold or humid—with stable temperatures around 15-17°C. Avoid extreme conditions, and your batteries will thank you with longer life and reliable performance.

You Shouldn't Mix Battery Brands or Types

True

When it comes to mixing batteries, conventional wisdom is not just marketing hype. Using different battery brands or types together in a device can actually impact performance and safety. Different brands may have varying chemistries and voltage levels, which can reduce efficiency when combined. While there has been some debate about mixing old and new batteries, particularly with AA alkaline batteries, which work independently, experts still recommend using batteries of the same type, capacity, and charge in your devices. This practice ensures optimal performance and helps prevent potential leakage issues.

It is Dangerous to Overcharge Your Phone Battery

It depends (but better safe than sorry)

In theory, lithium-ion batteries can be "overcharged," leading to safety risks like overheating or even catching fire. However, modern smartphones have built-in protection circuits that stop charging at 100%, preventing damage from overcharging. Additionally, smart chargers regulate power flow, switching to a low "trickle charge" once fully charged. While this means charging overnight is not inherently dangerous (in the case of new technology), it does contribute to battery wear over time. As a battery ages or becomes damaged, the risk of overheating, swelling, or fire hazards increases.

Although the fire risk in newer phones is low, charging overnight is still discouraged, especially as your battery ages. Excessive heat accelerates battery degradation, and older or damaged batteries pose a more significant safety hazard. Make sure to charge on a hard, ventilated surface and avoid flammable materials like pillows, blankets, or clothing. Never cover your device, as trapped heat can degrade the battery.

For battery health and safety, monitor charge levels, allow proper ventilation, and replace ageing batteries before they become hazardous. Despite technological advancements, many fire departments still recommend against overnight charging as a precaution.

You Can Test Batteries by Dropping Them

It depends (but it is a very bad idea)

You may have heard that you can check a battery’s charge by dropping it and observing how it bounces. While this holds some truth for certain alkaline batteries, this method is strongly advised against as it is often unreliable and can cause damage. Forcefully or repeatedly dropping certain types of batteries, such as lithium or rechargeable batteries, can be dangerous. Lithium batteries, in particular, can rupture, leak, or even catch fire if mishandled. Even with alkaline batteries, repeated drops can damage internal components, shortening their lifespan. To avoid risks and get an accurate reading, use a battery tester or voltmeter instead.

If you want to learn about using batteries safely, click here for a comprehensive handout.