Batteries are not mysterious black boxes that power your iPhone, in fact, they are quite simple products compared to the advanced silicon they are powering. The physical nature of batteries mean that they will ultimately wear out and become less useful over time, but device owners don’t need to worry.

Without getting too technical, these two chemical reactions are imperfect and introduce heat loss and wear to the battery. The lithium material slowly depletes, oxidization reduces usable surface area, and filaments grow from battery plates. All this leads to cell degradation and eventual battery exhaustion.

This occurred because these devices’ batteries had been exhausted to the point that they could no longer provide peak power during peak CPU draw. Since there were no other protections in place, the iPhone would sense the CPU power draw exceeding the available current and just shut down to protect the battery.

Lawsuits began and Apple made a public apology about the feature, stating it was always meant to make devices last longer, not force users to upgrade early. New iPhones starting with the iPhone X had much larger batteries too, which means it takes much longer for the battery to degrade past peak current draw.

Battery chemistry is affected by heat, charging speed, and the environment. In an ideal world, the longest battery shelf-life a person could achieve would be found if the room temperature was permanently 65 degrees, the iPhone only charged via a wire from about 20% to about 80% at about 10W, and the processor never got hot during use.

The air gap between coils, no matter how small, creates significant efficiency problems. As electricity passes through the charging coils, it generates a magnetic field, which interacts with the coils in the iPhone to provide a charge to the battery. This magnetic field is inherent inefficiency since much of the field is lost to empty air.

Coiled wire packed close together with electricity running through it gets really hot, so wireless charging pads tend to be warm surfaces. The coils in the iPhone heat up as well during power transfer, introducing yet another heat source. Overall, wireless charging is a very warm process that can affect battery chemistry long term.

Qi chargers exacerbate these issues due to poor alignment and a manufacturer’s tendency to use cheaper parts. Just because the iPhone begins charging once laid on a Qi charger doesn’t mean the coils are perfectly aligned, which increases energy heat loss, and reduces charging speed. More heat, means a battery that degrades more quickly as we’ve already discussed.

MagSafe helps alleviate some of these problems by having a higher standard for materials, as well as having magnetic alignment. Some chargers take advantage of the MagSafe magnets while offering only Qi 7.5W charging speeds, which is a decent medium. However, customers should seek out true 15W MagSafe chargers when possible to ensure the best charging experience and efficiency.

If you’re really worried about battery health, prioritize wired slow charging first, then fast charging, then MagSafe, and maybe avoid or minimize Qi charging. Of course, all available charging methods are safe, they may just lead to needing a new battery a month or two ahead of the expected two-year window.

I have an iPhone 11 that’s closing in on three years old. I just checked and the battery health is 88%, which I think is pretty good given the age. I never let it go completely flat, and I try to stop charging at 80-90% full. I always use the wired charger that came from Apple. (Tried wireless but it was so bloody slow I gave up the experiment after a few months). 

This go around I’ve been pretty diligent about keeping my launch 13 Pro between 20-80%.  If I’m not in a rush to top off I just use an old 5w iPhone charger brick from a few years ago.  I don’t just leave it sitting on the charger all day if I don’t need the phone.  It’s been about 10 months and battery health is still showing 100%.  

This content was originally published here.