Your iPhone's lock screen shows all kinds of things: date and time, notifications, playback controls when you're listening to music. In some cases, the iPhone lock screen displays information such as different colored battery icons or a thermometer..
Each icon gives you useful information, if you know what it means. It's important to understand what these icons mean and what you should do when you see them.
Red battery icon: Time to recharge
You may see a threatening-looking red battery icon if it has been a while since you last charged your iPhone (Read the article to save your iPhone battery life). In this case, your iPhone tells you that its battery is low and needs to be recharged. The charging cable icon under the red battery icon is another clue that shows you that you need to plug in your iPhone..
IPhone is still working while showing the red battery icon on the lock screen, but it's unclear how much time is left (unless you see your battery life. percentage). It is best not to push your luck. Recharge your phone as soon as you can.
If you are not able to charge it right away, you should try the power saving mode to conserve as much battery life as possible. See more on this topic in the next section..
If you're always on the go and still can't charge your phone, it might be worth buying a USB port portable battery to make sure you don't run out of juice.
Orange battery icon: power saving mode
You won't see this icon on the lock screen, but sometimes the battery icon at the top corner of the iPhone home screen will turn orange. This means your phone is running in power saving mode.
Power saving mode is a feature in iOS 9 and later that extends your battery life for a few more hours (Apple claims it adds up to 3 hours of use).
It allows you to temporarily deactivate unnecessary functions and modify the settings in order to extend the life of your battery as much as possible.
Green battery icon: charging
Seeing a green battery icon on your lock screen or in the top corner is good news. It means your iPhone battery is charging. If you see this icon, you probably know your iPhone is plugged in. Still, it's good to know how to look for it in case you're trying to charge it but there's something wrong with it.
Red thermometer icon: iPhone is too hot
Seeing a red thermometer icon on your lock screen is rare. It's also a little scary: your iPhone won't work as long as the thermometer is present. An on-screen message tells you that the phone is too hot and needs to cool down before it can be used again.
This is a serious warning. This means that your phone's internal temperature has risen so much that the hardware could be damaged (in fact, overheating has been linked to cases of iPhones exploding). There are a number of things that can cause this to happen, like: leaving a phone in a hot car or a battery related malfunction.
When this happens, the iPhone protects itself, according to Apple, by disabling features that might be causing problems.
This includes automatically stopping charging, dimming or turning off the screen, reducing the strength of the connection to the carrier's networks, and disabling the camera flash.
If you see the thermometer icon, immediately move your iPhone to a cooler environment. Then turn it off and wait for it to cool down before trying to restart it. If you've tried these steps and left the phone to cool for a long time, but still see the thermometer warning, contact Apple for help.
