batteryiosipad
As advertised with the release of iOS 9, Low Battery Mode can be activated on most modern iPhones to conserve power.
My question is, why doesn't the iPad support Low Battery Mode? It would seem to have the capability to – is there an official or proven answer as to why not?
(I am using an iPad Air 2)
If your phone shuts down with more than 10% charge remaining on the estimate, then you have a voltage / capacity issue in the battery and should have the device tested with Apple diagnostics to check the health of the battery. Think of a small town with a medium sized reservoir and a small water tower. The reservoir level can have water, but if it’s not pressurized (voltage) in the tower, the system can ask for more water (current) than the tower can supply. For a shower, the water just stops, but for an iPhone, it shuts off when the voltage drops too quickly.
The diagnostics read the low battery logs and compare them with thousands of other logs and Apple engineering standards to tell if your battery needs to be replaced.
Technically, those log files are total benefit with no downside. Your phone is out of juice and will shut down anyway. The OS is logging the data so you can take action on it if you choose. They don't cause anything other than logging what led up to the low power condition.
I watch my LowBatteryLog-YYYY-MM-DD-hhmmss.plist log files quite regularly to know when to seek service for my battery.
Technically, the lithium polymer cells can exhibit voltage drops when they are out of specification but not yet failing or in a state where they should be shut off and not used again.
Looking more deeply into your two posted logs, I would focus on these lines primarily:
Awake Time: 03:45:27 (13526)
Standby Time: 04:55:29 (17729)
Partial Charge: 0
Capacity: 0
Voltage: 3469 mV
When Partial Charge is 1 - that means that you plugged it in and the device received a charge between when it was full and first removed from power and it eventually shut itself off due to low power detection. In those cases, I really only focus on the Voltage - knowing when the device decided to preserve the remaining voltage for standby and battery protection.
The log above shows a very short awake time and indicates a likelihood that the battery isn't providing the correct duration and amount of power. Even if the CPU is full use, all radios are on, speaker cranking, brightness max - I expect 4 to 5 hours on most devices.
Unless that 3h45m run was a rare occurrence, my estimate is you need a hardware repair as sleeping more often will allow the sleep time to increase, but never increase the active time.
For newer iOS hardware (think iPhone 5 to 10) the voltage to available current to available capacity can also be due to aging, power management software or hardware issues.
Apple hasn't really discussed specifically what Low Power Mode actually does. Its main underdocumented feature is that it underclocks the processor, reducing performance to increase battery life, but there's a few other tweaks it makes to the system as noted underneath the switch.
As shown in these screenshots, Low Power Mode reduces the performance by ~30%.
Source: http://www.macrumors.com/2015/06/25/ios-9-low-power-mode-benchmarks/
Apple lists the following as features modified by Low Power Mode:
- Email fetch
- Hey Siri
- Background app refresh
- Automatic downloads
- Wi-Fi associations
- Some visual effects
Source: https://support.apple.com/kb/HT205234
More details are provided in the developer documentation (Energy Efficiency Guide for iOS Apps):
- Reduce CPU and GPU performance
- Pause discretionary and background activities, including networking
- Reduce screen brightness
- Reduce the timeout for auto-locking the device
- Disable Mail fetch
- Disable motion effects
- Disable animated wallpapers
Apple encourages developers to take advantage of this feature by implementing a lower power state in their apps. This means that this feature may increase battery life through support in third-party apps.
Your app should take additional steps to help the system save energy when Low Power Mode is active. For example, your app could reduce the use of animations, lower frame rates, stop location updates, disable syncs and backups, and so on.
Best Answer
'Why' is always difficult to answer.
That it doesn't appear to work on iPads would seem to be of concern to many people, but there doesn't appear to be any answer as to why.
See Where’s The Low Power Mode in iPad, iOS 9 Users Want To Know or
Low Power Mode Not Available on iPad in iOS 9: No Solution Till Now & others on Google. No-one seems to have any answers.