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.
Unfortunately there doesn't seem to be a way. As far as I know it charges to around 4-5% of battery capacity so that it's sure to be able to perform the whole boot process, even if it's unplugged, so not to screw something up when losing power while starting up the OS.
15-18 minutes seems long to me, though. It's usually 5-7 minutes using the iPhone charger.
Are you charging off a PC USB port?
Best Answer
I would question two things about your framing of the issue (and will sidestep the whole repair discussion/issue entirely):
1) Apple's warranty does cover batteries that don't retain a percentage of their useful life based on aging at one, two and three years (two for most iOS warranty / coverage, but there are exceptions in some cases). You should open a ticket with them if you have coverage and see if they will repair it for you.
2) I use an iPhone regularly outdoors when the temperature reaches -30 C and even then, the decrease in capacity is temporary. While the device is colder than 0C - you get less juice out of the cell, but once you warm it (in a pocket, next to your skin to warm it temporarily - or when you are inside a heated space for long enough to warm the battery), the devices recover full capacity.
(You will want to watch to control condensation to prevent liquid damage / especially if you bring a very cold device into a warm humid space, that warm air will carry liquid inside the product. Similarly, a warm device when rapidly cooled could have liquid condense inside it and then freeze.) Devices left in a car overnight such as iPad and Mac also see no measurable decrease in battery life once I get them inside and warm - whether I charge them or not.
I'll leave the DIY repair / pay for a repair discussion for another thread where you get specific on what model, but from what I see, the environmental behavior is that cold batteries still have all the charge they took, but they don't produce as much voltage and current while they are cold.