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iPhone SE 2, iOS 15.2, MagSafe wireless charger

From 11% to 31%: 1.21% per minute.

From 43% to 64%: 1.03% per minute.

From 63% to 68%: 0.87% per minute.

Do you think the speed is 7.5W or at least faster than 5W?

Zhang Wei
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    If the focus of your question has changed, please rewrite the question to focus on what you want to know and remove things which no longer are relevant. – nohillside Jan 06 '22 at 11:13

2 Answers2

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Are you charging from empty? Or at least from 50%?

The reason I ask is that over 50% charged phones (really all lithium batteries) eventually slow down charging by design. And a phone that is too warm will usually decrease the charging speed as well. This is why fast charging advertisements all mention the time from 0% to 50% or 80%.

In your iPhone 12 example, it reached 15W charging at 50% full. In your iPhone SE example, it reached 5W at 89% full. The first example is an excerpt and doesn't list the current battery level.

In my phone (iPhone 12), placing my 90% charged phone on 15W wireless charging starts the charging sequence at 15W, but it quickly falls to 5W. Connecting the same phone to wired charging at 20W shows it only wants 15W.

I assume if you retried you SE at about 50% capacity you should get your expected 7.5W of charging.

Edit:

For maximum clarity, you can purchase a USB power meter which will show the actual power draw. But you can also look up various charger statistics.

For the Apple 5W charger (from phonearena.com)

  • in 15 minutes: 14%
  • 30 minutes: 28%
  • 45 minutes: 43%
  • 1 hour: 57%
  • 1 hour and 15 minutes: 70%
  • 1 hour and 30 minutes: 81%
  • 2 hours and 30 minutes: FULL Charge

If your wireless charger is faster than this, then it can charge at 7.5W.

Dirk
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  • Thank you for your answer. As this comment doesn't allow me to type many words, I put my reply as well as update beneath my post. – Zhang Wei Jan 06 '22 at 10:42
  • According to the moderator's requirement, I removed the contents about that log in Mac Console application as well as the reply to you. See the log of this question please. – Zhang Wei Jan 06 '22 at 12:12
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Do you think the speed is 7.5W or at least faster than 5W?

This is a fundamental misunderstanding of what a watt (W) is in an electrical context. A watt is a unit of power. For current flow, a watt is equal to 1 volt multiplied by 1 ampre.

If a power adapter is rated at 7.5 watts, that doesn’t mean it will push 7.5W to a device; it means the device can draw up to 7.5W from the source.

With respect to the charging times and percentages, you simply cannot calculate wattage based on how much charge your battery has at particular time intervals. Why?

  • The initial charge level of the battery is unknown (what you see on your screen is a calculation based on spot measurements)
  • The battery age, cycle count, and current amp hours (AH) is unknown
  • The battery and cell efficacy is unknown
  • The battery chemistry and SEI layer is unknown
  • The power adapter specifications are unknown (yes, I know you’re trying to calculate this)
  • The device (iPhone) does spot measurements of battery voltage and calculates the percentage from known values. It cannot sense if a battery cell is faulty or working at optimum capacity.

To calculate wattage, you need to measure both voltage and amperage. Voltage is easy, using a multimeter, we can easily measure the output voltage of an adapter (we also know this from the USB specification: 5V). The amperage likewise must be measured, but the circuit must be under load. In other words, you can’t measure this without the device actually drawing current from the source.

The MagSafe wireless charger can deliver up to 15W of power. To see how much power is being drawn you can use a USB-C Power Meter while the phone is charging and record those measurements at defined intervals.

Once you have this information, you can calculate the watt-hours your device is charging; the speed at which your charger is currently working.

Allan
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