Why is my battery draining so fast?

Jul 12, 2019   Pageview:102

As batteries get older, their chemistry will start changing. This causes sudden battery drains. To truly understand why your battery is draining, you must learn about the safety circuits and chemistry of batteries.

Lithium ion batteries come built-in with a protection circuit that is supposed to protect it from abuse. This circuit also turns off the battery and makes it unusable when it gets overcharged, this is very important as overcharged lithium ion batteries are a serious safety hazard. Along with the issue of overcharge, lithium ions also have an issue of undercharging. Lithium ions cannot be discharged below a specific point, if the voltage of the battery falls beyond this point, the protection circuit will automatically shut off the battery. The battery now cannot be revived without using specialized chargers and analyzers that boost the battery back up and revive it back to its normal state.


Does a lithium ion battery draining fast all of a sudden?

There are two concepts that you need to know before you are able to understand why a lithium ion battery drains all of a sudden.

A lithium ion battery cannot be completely discharged to 0 volts and recharged back, thus they have a protection circuit in protection that cuts off the battery below a specific voltage. This is done because it will take special equipment to recharge the battery if the voltage falls lower than this level. Sometimes you cannot even recharge the battery using these special pieces of equipment.

Each time you place any load on a battery, the voltage of the battery will dip a bit. This is a natural process and it happens to all batteries. However, in new batteries, the dip is low, while old batteries have much higher dips due to their age and internal issues. The amount of demand that you place on your device affects this too, for example, playing games on your phone will cause a much higher dip than messaging. This is known as voltage sag.

When these two issues happen at the same time, the battery will rapidly drain. When your battery has a low charge and you put a sudden load on it, it will experience voltage sag. This voltage sag will bring the battery voltage below its cutoff point, thus effectively shutting it down. This causes the sudden battery drain that you might experience with your lithium ion battery. This effect is not noticed in new batteries because they have much lower voltage sag and will not shut down unless they reach very low charges. Old batteries, on the other hand, have much higher voltage sags, making the effect more apparent.

Why an iPhone 6 lithium ion battery draining fast all of a sudden?

Like any lithium ion battery, even iPhone lithium ion battery experiences voltage sag and has a cut-off point to protect it. When your phone charge is low and there is some heavy load on it, the voltage will immediately drop below the cut-off point. This shuts down the battery and this is the fast battery drain that you experience. The 0% battery charge that you observe in your phone does not actually mean that there is no more charge in the battery, but the 0% is actually the minimum point above which you can safely recharge your battery.

The controversial update that slowed Apple devices was designed to tackle this issue. The phones with weak batteries would have faced significant instant shutoffs without the update. By lowering down the performance of the device you will be able to lower the voltage sag, this will help significantly reduce the instant shutoffs.

What you can do when a lithium ion battery draining fast all of a sudden?

In most cases, your battery is draining very fast because it has gone bad. The internal chemistry and structure would have deteriorated. This can be caused due to physical abuse, excessive heat and will also occur as the battery grows older. The battery drain will especially happen if you had constantly drained your phone below 20% charge or held it over 75% for long periods. In cases like this, the battery cannot be brought back to its original state, it is better if you replace the battery. This is because damaged lithium ion batteries pose a significant risk, they can catch on fire and explode.


This could have also been caused due to excessive load. In smartphones and computers, this will happen if you are running a lot of power intensive applications. You should uninstall these apps to protect your battery. Sometimes even clearing the cache of your applications can help. The cause could also some bug in your devices operating system, in such cases, you must reinstall the entire operating system and format your device, do backup your files in another location before you do this.

If you are using your battery to power some other device, you will need to substantially reduce the load that you place on your battery. This is simply not possible in most situations, and will thus warrant a battery replacement.


Lithium ion batteries are a complicated concoction of chemistry and circuits. It has many safety features incorporated to protect both the users and the battery. One of these features is a cutoff point below which the battery will switch off. When this is combined with the voltage dip that batteries face when placed under load is what causes the fast draining. The only way to prevent this would be to lower the amount of load you place on your device, this can include uninstalling applications and unplugging a few devices from your battery. However, if your battery has become too old, these steps will not be able to make much of an impact. It is best that you replace the battery at this stage.

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