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Till XS Max and prev generations of iphones I owned, I used to put it on the (wireless) charger whenever the battery went below 50%.

On iphone 11 pro max I no longer do it. I just get it charged using the PD fast charger every day morning. it takes little time to topup now and charge stays much longer, so I never worry about it.
 
The advice I have gathered over the years reading iPhone/iPad batteries and my personal experience can be summed up as follows:

1) For a good battery health, it needs to be exposed to different charge/discharge levels, so fluctuate regularly between 90% and 15-20%. Do not be afraid to let your battery run low. Aiming to keep it at a 100% is not a good strategy. However, if you charge it slowly (see below) at night and it gets to a 100%, it is totally fine as the device will just stop taking power in once charged completely.

2) It is better to charge a Lithium-ion battery with the least powerful charger possible. This is the reason Apple still ship iPhones with those “weak” chargers in the box. Sure they take longer to charge your device to a 100%, but are much better for the battery health.

3) When you have a choice, charge it in a cool/cold environment. Attaching the phone to a windscreen of a car (heat exposure) and having it plugged into a charger at the same time is really bad for the battery!

Having said that, Apple are continuing improving the power/battery management on their latest iPhones and iOS 13, which should help.
 
The advice I have gathered over the years reading iPhone/iPad batteries and my personal experience can be summed up as follows:

1) For a good battery health, it needs to be exposed to different charge/discharge levels, so fluctuate regularly between 90% and 15-20%. Do not be afraid to let your battery run low. Aiming to keep it at a 100% is not a good strategy. However, if you charge it slowly (see below) at night and it gets to a 100%, it is totally fine as the device will just stop taking power in once charged completely.

2) It is better to charge a Lithium-ion battery with the least powerful charger possible. This is the reason Apple still ship iPhones with those “weak” chargers in the box. Sure they take longer to charge your device to a 100%, but are much better for the battery health.

3) When you have a choice, charge it in a cool/cold environment. Attaching the phone to a windscreen of a car (heat exposure) and having it plugged into a charger at the same time is really bad for the battery!

Having said that, Apple are continuing improving the power/battery management on their latest iPhones and iOS 13, which should help.
2. It's true to charge as slow as possible to maintain health, but that's not why apple includes the 5w brick with the 11 (and each phone last year). They did it purely to upsell you their fast charger. What kind of company touts fast charging for the first time ever with the X, yet didn't include a fast charger. Same thing with the xs. They know the 11 will outsell both of the pro models this year, and they can pretty much count on selling 11 owners a fast charger by the boatload. It's a shame Apple makes the best products for a lot of us, because you get more for less with Android. My POS work Android has a 5000mah battery, face id, fast charge and sd card compatibility to add more storage, all for $250. Fast charging isn't a luxury these days, unless you're Apple.
 
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