I use the included lightning to usb-c cable to charge my iPhone 12 by connecting it to my macbook pro (2017). I've heard that reducing the charging current is potentially beneficial to the battery. If so, is there a way for me to limit the amount of current available to the iPhone (for example, to the standard 1A)?

Current current data:

  Available Current (mA):   500
  Required Current (mA):    500
  Extra Operating Current (mA): 1900
  Sleep Current (mA):   2400
  • It's already self limiting, it will slow down over 50% charge & then stop at 80% until your usual disconnect time. It's also only running at the standard 500mA iPhone max anyway.
    – Tetsujin
    Jan 9, 2022 at 13:14
  • @Tetsujin Thank you for pointing that out! I compared this to a SSD and confirmed that the iPhone is indeed only drawing 500mA if the data reported is accurate. But if it only uses 500mA, why does it have the higher extra operating current / sleep current?
    – Joy Jin
    Jan 9, 2022 at 13:21
  • That's what the MBP can output if requested. I don't have an MBP here to compare.
    – Tetsujin
    Jan 9, 2022 at 13:29

1 Answer 1


There's no need to reduce the amount of current available to the iPhone as the iPhone itself will not draw more power than it needs or more power than is "good for it".

If you still want to do this even though it is not a good idea, you cannot do it on the Mac.

  • While the OP shouldn't worry about short-term damage to a battery or starting a fire, it's still an excellent idea to avoid fast charging if you're looking to prolong the lifespan of a battery. See e.g. figure 3 of this article. I personally put a high value on the lifespan of my battery, and always limit current by using the old 5 W chargers, or hacks to achieve even slower charging.
    – swineone
    Mar 13, 2022 at 2:42
  • There's something missing from your argument I think. You refer to figure 3 in the article, which shows that if you charge at a higher rate than 1C, you're more than linearly degrading the battery capacity over time. I.e. if you value your battery lifespan, don't charge it faster than 1C. However, Apple's Fast Charging feature is advertised as "charge to 50% in 30 minutes" - which is exactly the rate of 1C.
    – jksoegaard
    Mar 13, 2022 at 14:56
  • Quoting from the article: “The longevity can further be prolonged by charging and discharging below 1C; 0.8C is the recommended rate.” Moreover, fast charging usually results in higher temperature, whether directly in the battery or in nearby power circuitry, which usually conducts to the battery. And temperature is enemy #1 of a battery, which is also the reason I never use wireless chargers.
    – swineone
    Mar 13, 2022 at 18:32
  • I’m still not convinced by that argument. The charge rate they talk about is the average over many charges - you’re not fast charging all the time, so your average charge rate is not 1C - it’s considerably less. Whether or not a harmful temperature is present depends on how well the thermals of the phone are designed. I have seen no evidence that there’s any meaningful loss of capacity over a reasonable amount of time (for example 3 years) by disabling fast charge religiously.
    – jksoegaard
    Mar 13, 2022 at 18:40
  • I admit I’m way more paranoid than most people when it comes to battery lifespan since I live in a warm country and a battery swap is twice as expensive (in dollars, never mind a purchasing power matched comparison) as in say the US. I just do what it takes to lessen battery degradation over the 3-4 years I keep my phone. Doesn’t mean I wouldn’t fast charge if SoC was low and I was pressed for time, but I do try to plan ahead to avoid it. Also, it’s plain to anyone who touches a phone while fast (or wireless) charging that it is warmer than on a regular (5W) wired charge.
    – swineone
    Mar 13, 2022 at 19:06

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