I’ve read articles online over the last month that suggest charging an iPhone 8, 8 Plus or X wirelessly will cause the phone long-term battery damage. Perhaps increasing the charge cycles and causing the phone to need a replacement battery sooner than is ideal. I have problems with this, and I want to write a counter argument and explain why I think these stories are wrong.
The stuff I’ve seen seems to stem from a ZDNet article. Now I’m not interested in a fight, but my understanding of how wireless charging works is different. I’ll explain: In the article the claim is made that during a wireless charge an iPhone is powered from its battery, not the charger. This is, I believe, incorrect.
I’m pretty certain when I say that this is wrong scientifically. A battery can’t be charged and discharged at the same time, this is simply not possible. When you place a phone on either a wireless charger, or a cable-based charger, you are providing enough power for both the phone to run, and the battery to charge. The phone is operating on mains power, and the leftover goes into the battery. On low output chargers (wireless included) this might lead to slow battery charging, but the process is always the same.
The watts coming out of the charger will first power the phone, with anything left charging the battery. If the charger provides 5 Watts, the phone operates using 2 Watts then the battery can have 3 watts.
So wireless or not, the cycle is the same. However what Adrian Kingsley-Hughes noted in his article was that his phone had done a lot of “charge cycles” for its age. This, I think is somewhat true because when you place a phone on a wireless charger and top it up you’re basically completing a cycle. If you’re like me, I put my phone on a wireless charger on my desk when I’m at it. This could mean that my phone is dropping to, say, 80% then being topped back up to 100%. If I do that twice, then the phone has done two cycles in a day.
What Kingsley-Hughes suggests is that this is bad news. However uses Apple’s wording here says that it designs batteries to last 500 cycles and to retain 80% of their original capacity. It does not, however, suggest that this is a hard and fast number. You might get to 500 cycles and have 90% of the original capacity. An iPhone (or Galaxy S9) may actually last through 1000 cycles retaining 80%. If you mistreat the phone and the cell overheats, you’ll see way less.
Could wireless charging cause damage to a battery some other way? I’m pretty sure not, the big way to cause problems in smartphone batteries is to overheat them. Wireless can create extra heat, but I suspect it’s not enough to shorten the life of the cell.
Of course we’re making $1000 investments in phones these days, and we don’t want to ruin them. So I have sympathy with the idea, and desire to protect our phone batteries but my instincts are telling me that the reasoning on this one is wrong. If you’re worried, avoid putting your phone on the charger unless you actually want it to top up. At least that way you’re lowering the number of cycles the battery goes though. This advice is the same for both cables and wireless chargers – certainly try not to worry about this stuff – life’s too short.
