25w charging brick on my iphone 12

It should be fine as long as you trust the quality of the power supply. The phone controls/limits the current/power that it accepts. A power supply (like a power adapter, USB power bank, computer, etc) doesn't force current. It's a voltage-controlled source - typically with a maximum output rating. One could theoretically have a 500W capable power supply and it should be fine as long as the voltage is steady at 5V or 9V, the same way that a night light that uses 0.5W can be plugged into an outlet rated to supply 1800W.

If you're really concerned, it's also safe to use older USB-A power adapters and USB-A to Lightning cables. The would limit the max charging current. Even though newer iPhones accept 5V or 9V input, the battery charges at less than 5V, but I believe current with 5V would be limited.

It is normal for batteries to become warm during the charge cycle. This is caused by the energy the charger is putting into the battery. In general, the larger the charge current, the warmer the batteries will become, I also fast-charge iPhone 12 Pro with a 20W charger and sometimes with my 61W MacBook Pro charger, if I need to bring it out and I forget to charge. Its okay if the iPhone is hot, but not too hot at the point where it feels that you touch a preheated oven.

Hi,

The following articles should be able to further assist:

• Fast charge your iPhone
• Identify counterfeit or uncertified Lightning connector accessories
• About Apple USB power adapters
• Charge your iPhone with an iPad or Mac notebook power adapter
• About the Apple USB-C to Lightning Cable
• Using Apple power adapters, cables, and duckheads with Apple products
• How to wirelessly charge your iPhone
• How to use MagSafe Duo Charger with your iPhone and Apple Watch

EugeneAskWhy wrote:

It’s okay to use third party Made For iPhone bricks (MFI Certified), these bricks brands like Anker are good and well known for MFI certified Products.

It's not totally necessary, but it takes some judgement. I haven't seen any USB-C power adapters that are marketed as MFi unless they might have something like a captive Lightning cable.

It’s okay to use third party Made For iPhone bricks (MFI Certified), these bricks brands like Anker are good and well known for MFI certified Products.