The iPhone 13 Pro Max launched in 2021 with the largest battery of that year's iPhones, 4,352 mAh, and was praised for its endurance, so a drain that now seems fast is almost always the battery's age or a setting. Apple's Battery Health screen, Settings, Battery, Battery Health, shows maximum capacity as a percentage of the new battery; on a phone of this age it is often in the eighties, and Apple treats 80 percent as the line below which service is recommended.
The checks in more detail
The screen is a ProMotion 120 Hz display, which draws more power at high brightness, so Settings, Accessibility, Motion, Limit Frame Rate to 60 saves battery. Background App Refresh, Location Services set to Always, and widgets that refresh often are the usual silent drains. 5G is another: Settings, Mobile Data, Voice and Data, 5G Auto switches to LTE when 5G does not speed things up.
Low Power Mode adds hours. After a major iOS update, expect a few days of poor battery while the phone re-indexes. A phone that drops from forty percent to shut down suddenly has a battery that cannot deliver peak power, which a battery service fixes. Apple's page also says to check Peak Performance Capability, which reports whether the battery can supply peak power; a message that performance management has been applied means the phone slowed itself to avoid shutdowns, and a battery service fixes it.
You can turn the feature off in that screen only after an unexpected shutdown. Check also that the phone is not stuck in a loop of syncing a large iCloud library or a backup, which keeps the processor busy for hours and drains the battery; Settings, your name, iCloud, Photos shows the sync state, and plugging the phone in on Wi-Fi overnight lets it finish.
Differential
Likely causes of “Apple iPhone 13 Pro Max battery drains too quickly”, and how to tell them apart
- 1
A battery with reduced maximum capacity
What separates it Battery Health shows a figure near or under 80 percent
How to confirm Book a battery service
- 2
The 120 Hz ProMotion display
What separates it The screen is the largest user
How to confirm Limit Frame Rate to 60 in Accessibility, Motion
- 3
Background refresh and Always location
What separates it Apps use power at idle
How to confirm Limit Background App Refresh and set location to While Using
- 4
5G in weak coverage
What separates it The radio drains quickly
How to confirm Use 5G Auto or LTE
- 5
Post-update indexing
What separates it Drain for days after an update
How to confirm Leave it on charge and wait
Before you touch a setting
Record this first — changing settings destroys the evidence
- The maximum capacity and peak performance message
- The top apps in Battery
- The signal and 5G setting
- The date of the last iOS update
Try in this order
0 of 8 completedCheck Battery Health
ReversibleSettings, Battery, Battery Health.
Limit the frame rate
ReversibleSettings, Accessibility, Motion, Limit Frame Rate.
Limit background refresh
ReversibleSettings, General, Background App Refresh.
Set Location Services carefully
ReversibleSettings, Privacy and Security, Location Services.
Use 5G Auto
ReversibleSettings, Mobile Data, Voice and Data.
Turn on Low Power Mode
ReversibleWhen you need hours more.
Read the Peak Performance message
ReversibleIn Battery Health, note whether performance management has been applied.
Judge after a week
ReversibleAfter an update, give the phone a week to settle before deciding.
Model-specific
What is true of this model and not of its siblings
- The biggest 2021 battery
- It was rated for long life when new.
- ProMotion
- The 120 Hz display adds drain.
- Performance management
- The phone slows itself when the battery is weak.
- Settling time
- Battery life dips after updates.
Stop boundary
When this stops being a self-service repair
- !If maximum capacity is near 80 percent, ask Apple about a battery service
- !If the phone shuts down suddenly with charge left, book service
- !A swollen battery means stop
Evidence ledger
Sources behind this answer
Exact questions
Common questions
How long should an iPhone 13 Pro Max battery last?+
About a day when healthy.
Does 120 Hz drain the battery?+
Yes.
What is maximum capacity?+
The battery's capacity compared with new.
When should I replace it?+
Below about 80 percent.
What is performance management?+
The phone limiting itself to avoid shutdowns.
How long after an update?+
About a week.