Is fast charging of your smartphone bad for its battery?

Fast charging is a convenient way to replenish your phone’s battery, provided your device supports it and you have a charger that can output the required wattage. But does this time saver negatively affect battery life?

Charging works in stages to protect the battery

Fast charging is not inherently dangerous to your phone’s battery. Fast chargers cannot “overload” the battery because the smartphone will only require an amount of power the device can handle. This means that you can safely use a USB charger that will pump more wattage to your device’s maximum charging rate.

The smartphone battery can only use fast charging for a limited time. This is because lithium-ion batteries charge in three stages: a slow “trickle charge”, a constant current state where the voltage increases over time, and a final constant voltage state where the current is slowly reduced to prevent overcharging and damaging the battery cell.

Fast charging only works during the steady current state, which is why many smartphone manufacturers advertise a fast charging window, for example, “Charge up to 50% in 30 minutes” or something similar. Once the final constant voltage phase begins, charging resumes at the standard rate.

Fast charging may generate more heat

The faster energy is stored in a lithium ion cell, the more heat is generated. This means that fast charging generates more heat than standard “slow” charging. This can be a problem because excessive heat will degrade lithium-ion batteries. Fast charging may shorten battery life compared to using a standard charger.

Most studies looking at the heat from fast-charging lithium-ion cells focus on electric car batteries, which are much larger than batteries in smartphones. The results of these studies indicate that some fast charging methods degrade the cell at a much faster rate than standard charging.

Since extreme temperatures are the enemy of any lithium-ion battery, using your phone in an extremely hot or cold environment or leaving your device in full sunlight can also damage the battery.

To get the most out of your battery, keep a quick charge on hold for the times when you need to charge your smartphone quickly. Use a standard charger at other times when you have time.

Replaceable smartphone batteries

Smartphone battery replacements are relatively affordable compared to the price of a new phone. Apple charges between $49 and $69 (depending on the device) for an out-of-warranty battery replacement that will return your device to a new condition in terms of battery performance.

Many Android devices have user-replaceable batteries, while others can be serviced by the manufacturer or a third party for a moderate fee. User can service both iPhone and Android devices with new battery using parts and manuals available from sources like iFixit.

Batteries will degrade over time even with perfect use. Understanding when to replace the battery (and how this can increase performance) can help you.