If you have an iPhone, iPad, or iPod, you might have noticed something a little odd about the way it charges: fast up to a certain percentage, then slower and slower as it gets closer to 100%. I noticed this a few weeks ago, and since I know practically nothing about current, electricity, volts, amplifiers, chargers, etc., I was not sure if my iPhone should be charging this way or not.
In the end, I tested it on the iPad as well and realized that it does the same thing. It charged pretty quickly to around 70-80% and then slowed down significantly before reaching 100%. In fact, according to my calculations, the time required to go from 1% to 80% was about the same as to go from 80% to 100%!
In this article, I will explain what little I have learned and understood about charging Apple products, and hopefully give you some idea of ??what exactly is going on. If you are an engineer or someone who knows a lot about this topic, do not hesitate to leave your thoughts in the comments!
Energy sources versus chargers
The first thing to understand is the difference between a power supply and a charger. You have probably said the following statement at least once in your life when you own an Apple device: “Where is my charger?”
Unfortunately, this statement is technically inaccurate. The cable and adapter that you plug into the wall is really just a power supply. It draws current from your wall and supplies the specified amount of amps and watts to your iPhone, iPad or iPod. The Charger is actually in the device itself. That’s why you can use an iPhone charger to charge your iPad or an iPad charger to charge your iPhone.
The charger inside the iPhone or iPad controls the flow of current into the device, not the adapter. If you’ve ever checked, the iPhone adapter is rated for 5W 1Amp. IPad adapter rated for 10W 2.1A.
IPhone and iPad charger
The battery inside your iPad or iPhone is a lithium-ion polymer battery. This is what Apple uses on all of its devices, including Mac computers. Apple has a great page that explains a little about their battery technologies, but the best part is the table they provide:
Let’s take a look at this graph. On the Y-axis, we have the current voltage (A / V). A for amps and V for volts. The first number is amperes, the second is volts. On the X axis, we have the charging stages: fast charging and continuous charging. Stage 2 explains why your Apple device slows down and takes longer to charge when the charge level is above 80%.
As you can see, the number of amps stays at 1 (for iPhone, 2.1 for iPad) for the first two hours and then drops to zero over the next two hours when the device is fully charged. You’ve probably also noticed that sometimes when you unplug your iPhone or iPad from the charger, it can be anywhere from 96% to 100%. This is due to drip charging. When it reaches 100%, it shuts down. If the battery starts to run out, it will return to about 96% and start slowly charging again.
Why do we need lean charging?
The question arises: why the hell do we need a recharge? Why not just quickly charge up to 100% and be done with it? Well, obviously it has to do with the chemistry of lithium ion batteries, which I have no idea about. In short, lithium-ion batteries respond very poorly to overcharging and therefore you never want that to happen.
Trickle charging solves this problem by reducing the current in the last stage of charging and stopping it completely once the battery is fully charged. This is why it is also not harmful to leave the device connected to a power source even after it is fully charged.
In conclusion, the charger is inside your device, and what you plug into the wall is the power adapter, not the charger! All of this technology is designed to extend battery life over many charge cycles. If you have any questions, let us know in the comments! Enjoy!