Here’s why your phone battery drains even though your phone is turned off:
The reason that your battery drains even when the phone is off is that the battery is incapable of holding a charge forever.
The raw physics of how batteries work forces them to slowly lose charge over time, even if they aren’t powering anything. This, the age of the battery, and its environment all play a part.
So if you want to learn all about why your phone battery drains even when it’s turned off, then this article is for you.
Let’s jump right in!
What Is Draining the Battery of Your Cell Phone?
For the most part, there are two things that drain your battery even when it’s turned off. Those are trickle charge and self-discharge. They are very different physical things that happen to batteries, but both of them happen to all phone batteries.
No matter how new or advanced your phone might be, it is still subject to these principles.
Trickle charge is inherent to all electrical systems, big or small. It’s based on how circuits work in the first place.
In order to have a circuit that conducts electricity and does any of the countless things we use electricity to do, the circuit has to be complete. That is, there can be no gaps in the circuit between where the electricity originates and where it terminates.
A simple example can help. Let’s say you have a battery-powered flashlight. Let’s also assume it’s as simple as possible in terms of design.
In the flashlight circuit, electricity flows from the battery to the light. In order for that to happen, there can be no gaps between the battery and the light. If there are, the light can’t shine.
If the light isn’t on, that means the circuit is not complete. Despite that, you still have a conductor attached to a battery, and ultimately, that circuit has to end somewhere.
At the end of the circuit, whatever is attached to the wires can absorb small amounts of electricity. So, even when the flashlight is off, a tiny amount of electricity is draining from the battery into the environment.
It’s not enough to cause danger anywhere. It’s not enough to quickly drain the battery.
But, if you’ve used traditional batteries, you might have noticed that they last longer in the package than in an unused flashlight. Trickle charge is why.
Trickle charge is exacerbated as the systems grow more complex.
As circuits get more complicated, you add things like capacitors to the system. These are devices that stabilize the current and help make the system work a little more regularly.
They also successfully comp[lete a circuit even when a device is off. That means that systems with capacitors experience more trickle charge than systems that don’t have capacitors.
Getting back to your phone, there are small capacitors in the system. So, when the phone is off, each capacitor is slowly draining the battery. It’s why most phones lose noticeable amounts of charge when they are turned off for a few days.
There’s a second issue at play. Even in the absence of trickle charge, batteries experience what is known as self-discharge. This is a process by which batteries lose a little bit of their total charge over time.
This is different from trickle charge because it even happens to batteries that aren’t attached to a circuit. It’s part of the chemical nature of how all batteries work.
In order to charge a battery, it actually undergoes a chemical change. This is why all batteries eventually stop holding a charge. Each time that chemical process happens, the lifespan of the battery goes down a little bit.
With self-discharge, the chemical nature of the battery allows it to act upon itself. A charged battery has a lot of electrical potential. That potential actually attracts and repels other parts of the battery, and it creates electric fields that can alter the nature of the battery.
This all happens on a pretty small scale. The bottom line is that a charged battery slowly but surely uncharges itself because of how electricity and batteries interact with each other. To date, there are no batteries that can overcome this.
Overall, self-discharge isn’t huge. For the average phone, it would take a week or more for the average battery to drain because of self-discharge (adding trickle charge to the mix can make batteries drain a lot faster). If this does happen, you can just plug in the phone and recharge the battery.
As batteries age, they undergo those chemical changes mentioned above. These changes lower the battery’s capacity to hold a charge. The overall wear and tear means that the battery can’t last as long between charges as it used to.
Age also causes self-discharge to accelerate. As the battery gets more and more chemically depleted, it is less able to resist self-discharge. What used to take a week or more can happen in a day or less when a battery is near the end of its life.
Why Is It Worse for Cell Phones?
All of that is simple enough, but why do cell phones drain so fast when other things don’t? Smart remotes can go months between charges. Meanwhile, a phone battery can drain in a matter of days.
The answer to this is found in a few things. First, as you already know, more complicated systems have more capacitors. Phones have a lot more trickle charge than your standard smart remote.
Second, phones and their batteries are subject to a few situations that are less common for remotes and a lot of other electronic devices.
One thing happening here is more psychological than physical. Most battery-powered devices don’t give you a clear indicator as to how much charge is present when you turn it on.
Computerized devices are the exception. So your laptop, tablet, and smartphone will all let you know exactly how much charge you lost while the device was off.
This can make trickle charge, and self-discharge effects feel worse than they really are.
Why It’s Never 100 Percent When You Turn It On
Most phones also don’t actually fully charge the battery. This is because the time to charge a battery increases as you get closer to 100 percent.
So, with a fast charger, you can get a 50-percent charge in a matter of minutes. You can usually get a 90-percent charge in under an hour. Then, it will usually take multiple hours to get above 95 percent from there. Getting to a genuine 100-percent charge can take days.
Some phones will round up to 100 percent when you get close. Others will pretty much never display 100 on the charge level.
There’s also an issue with temperature. Phones tend to go with us wherever we are. Sometimes, that can include a journey into very hot or very cold weather. Extreme temperature changes impact the battery and can reduce its capacity to hold a charge.
As long as the temperature changes aren’t too intense, these changes are temporary. If a phone is kept below freezing or above 120℉ (49°C) for more than a few minutes, the changes can actually become permanent. Extreme temperatures are very bad for batteries and for phones in general.
Do All Batteries Drain When the Phone Is Off?
To date, there are no phones that are immune to drain when your phone is off. It’s just how batteries work.
That said, the performance of the battery will change depending on how it is made. The best batteries last a lot longer in this scenario.
Lithium-ion batteries are the most common rechargeable batteries in the world. The vast majority of phones use them. The reasons for this are that these batteries charge faster and hold their charge longer than their predecessors.
That’s why modern phones actually see less discharge while turned off than a lot of earlier phones. When they were still using nickel and cobalt in the batteries (the ones that would swell a lot when they got old), the batteries would often completely drain even while the phone was off.
These days, a healthy lithium-ion battery can usually last several days while a phone is off. Sometimes, they can last more than a week.
Lithium polymer batteries are newer and exciting. They are starting to replace lithium-ion batteries in many applications. For now, they’re still less common.
These batteries are still made with lithium-ion technology, but the polymer electrolyte holds the battery in a different medium. In simpler terms, the battery has less fluid inside of it. That subtle but important change allows these batteries to charge faster and last longer than traditional lithium-ion batteries.
Because they aren’t used widely enough, it’s hard to put a solid number on the difference. But, in general, you would expect a lithium polymer battery to drain even slower when a phone is off.
It could potentially last upwards of a week on average. But, it would still mostly depend on the health of the battery and the phone’s external environment.
What Can Be Done to Stop Battery Drain of Your Cell Phone?
The most important thing to remember is that your phone will drain over time. As that happens, you’ll notice this issue more and more.
You can’t prevent your phone from aging, but you can extend its life. There are two ways to do this. First, try to only do heavy phone usage while it’s plugged in.
While older batteries were prone to overcharging, it’s impossible with lithium-ion technology. Putting stress on the battery is the worst thing, so if you’re going to play games on the phone or watch ultra-high-def videos, plug in the phone as much as possible.
Second, don’t drain your phone all the way. If it happens every once in a while, the battery will be fine. But, running the battery until the phone dies is stressful for the battery. Avoid it when you can.
On another note, learn all about whether your phone goes straight to voicemail when the battery dies here.