The hidden challenges and limitations of fast charging in smartphones

Smartphone manufacturers love to compete with each other and that’s especially true when it comes to hardware specs. While design, user experience and build quality are things that are hard to measure exactly, specs usually come with nice, specific numbers that you can compare and confidently say “X is larger than Y” which obviously means X is better, end of story.

That’s how we end up with all the different races between phone makers: whose phone has the most processor cores or amount of RAM, the biggest battery, and most recently, the highest charging speed.

But improving charging speeds isn’t as easy as putting a massive power adapter in the box and calling it a day. Just like you can’t just change the engine of your car with one that has 500 more horsepower without also changing the gearbox, brakes, suspension and so on, you also have to beef up the whole power infrastructure of a smartphone to shave off those extra minutes of charging time.

Let’s look at all the major parts of that puzzle and what obstacles manufacturers face when trying to bring down charge times. Starting with…

The charging adapter 

The humble power adapter is the unsung hero of every fast-charging technology. Regardless of its make or model, your phone will never reach its peak charging speed unless it is paired with a capable power adapter.

The challenge in designing a modern power adapter lies in enabling it to deliver lots of power safely and efficiently. That's because modern smartphones come with bigger and bigger batteries, and these need more powerful chargers to charge quickly. But a more powerful charger has to be either physically larger or made using a more efficient circuit design. Thankfully, things have greatly improved on the latter front. Had the Galaxy Note 10's 25W power adapter – which is about as big as two TicTac containers – been built using the tech inside a Nokia 3310's adapter, it would have been the size of a soda can.

Speaking of evolution, a modern power adapter is much more sophisticated than a counterpart from only a decade ago. No matter what fast-charging technology it supports, specialized chips inside of it allow it to communicate with the phone throughout the charging process. This allows the phone to request the optimal amount of power, depending on the battery's charge level and temperature. All of this is done in the name of speed, efficiency, and safety.

Cable and connectors

But a powerful, efficient charger would be of no use if it has to squeeze all that power through a cable that’s not meant to handle it. While cables are undoubtedly the simplest part of the charging infrastructure, they’re just as important as any other. The challenge here depends on how each manufacturer decides to transfer the power from the adapter to the phone.