Standard charger wattage for iPhone 15

Does using less than a 20W charger improve the life of the battery? Is it less damaging to use a lower wattage and thus improve the lifespan of the battery? Or is the battery optimized for 20W?

at the end i didn't really get it

for longer battery life span it's better to use 12W or 20W?

but isn't it better to use a 12W adaptor for iphone 15 promax since it generates less heat than the 20W one?

You need USB-C (for the correct connection type) so any Apple charging adaptor with a maximum output rating 20W or higher will be good for either a wired connection or MagSafe. Note the power rating is simply the maximum an adaptor can provide. Your iPhone is smart and will only take as much as it needs even if it is only a few % of the charger's rating, you should not need to worry about fast or slow charging.

If you want to continue using an older USB-A charger/adaptor I know the 10W or 12W units will work, and even lower will probably work but not tested. You will probably need to look at a Lightning to USB-C adaptor so you can continue to use your existing Lightning cables from a previous iPhone. Apple list a suitable device on my home store (UK) and it will exist in other regions but you might have to search

USB-C to Lightning Adapter - Apple (UK)

This adaptor is also useful if you have USB-A sockets in the car and need to charge on a long road trip.

Standard/recommended is an Apple 20W charger, or a 3rd party charger supporting USB PD (USB Power Delivery), bearing in mind that the charger doesn’t “push” power; it just supplies the power “drawn” by the device.

Take a look at this support article too:--> Fast charge your iPhone - Apple Support

Regards

Giulio

From this support document from Apple, Fast charge your iPhone - Apple Support

You need a 20W or higher power adapter to fast charge your iPhone 12 and later. Anything less will not fast charge the phone. I use the 20W on my iPhones and have not experienced any problems.

So which will charge faster an apple cube 20w or an apple cube 35w ? Or does the 15 pro max only pull 20 w no matter what cube it is hooked up to if higher than 20?

The battery will only take what power it needs. That is one of the great things about how the charger in the phones and other Apple products work. If you generally charge your iPhone overnight to get the advantage of having a fully charged phone in the morning and letting it backup automatically to iCloud, you can use one of the lower wattage power adapters. And if you have optimized charging turned on, it will learn your charge pattern, then charge to 80%, then slow down to finish to 100% just before you would normally be disconnecting it. You can look over this document from Apple about batteries and charging. About Optimized Battery Charging on your iPhone - Apple Support and this one as well. Batteries - Maximizing Performance - Apple

Won't hurt to use the 35W cube, but it also won't really help.

The "charger" is in the phone and it controls the "charge" at about 20.

I only have my own experience with my own test equipment. Have not looked further than that because I believe what I see.

But maybe someone else will post to say that the phone charges twice as fast at 40W than it does at 20W.

As I said, it won't hurt to use a 35W supply, but it also won't help as far as charging the phone. The larger supply won't be working as hard to supply the 20W, so might run a bit cooler if that is important.

Thank you for that answer. Any data anywhere that I can look at that info. I think that is what the Apple Store told me that I didn’t need over 20 W. But everyone I know is using a 30 or 35 to get faster charging, so they say.

I no longer have test equipment handy, but the phone "pulls" about 20W from a 35W-85W power supply.

Your friends will be disappointed to learn this, so you might want to hold off on breaking the bubble for them.

So if I read that correctly, no matter what charger you’re using, what cube, if it’s 20 all the way up to the 100 it will charge at the same speed, correct? Just looking for data to back that up before I trade in my 20 W cube for a higher one.

If you’re REALLY interested, there’s a decent USB-C VA Meter available for abt $25 which can be used to settle arguments.

It’s the size and shape of a “normal” USB thumb-drive and has a built-in display screen.

If you’ve got a “tech mindset” it’s also interesting to watch how the USB-PD negotiates voltage and current for different devices AND how the battery acceptance rate falls-off as the SoC increases.