Why Do Batteries Deplete Their Charge When Not in Use?

You fully charge a tablet or a power drill battery pack, tuck it away, and forget about it. The battery is dead the next time you take it out. How come? The following explains why batteries cannot and do not stay charged.

Over time, all batteries lose charge

Let’s examine the main overall notion associated with this subject before delving into the many battery types. Energy seeks to achieve balance by moving, not by being still. Consider the straightforward case of house heating and cooling. You must constantly add heat to your home during the winter since it transfers heat energy into the chilly surroundings. Additionally, throughout the summer you must constantly expel heat while fending off outside energy.

Batteries are a small technical marvel, despite the fact that we take them for granted. With the help of batteries, we have amazingly developed a system that allows us to temporarily store electrical energy in a small space and use it when needed. For the most part, the energy stays put and doesn’t leak out into the environment.

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But the electrical energy we store in batteries is comparable to a group of students crammed into a classroom. The kids are antsy and fidgety, and they really want to go outside the classroom, running around the playground. You might readily counter that youngsters do not naturally remain quiet and still in orderly rows.

Your battery’s electrons are like those restless children; they are itching to get free and start moving around once more. Batteries may be highly deadly when things go wrong because the chemical components inside them do not naturally arrange themselves into calm, orderly rows. Even if your gadget is fully off or the battery is totally detached, as is the case with power tool batteries that have been removed from the tool, it is still not truly off at the atomic level.

Although considerably more muted than when the battery is being used, the chemical activity inside the battery that creates the battery is still happening. The battery’s internal low-level activity progressively uses up the energy that is being stored. Electrical discharge that occurs when a battery is not being loaded externally is known as self-discharge and cannot be prevented.

various battery types discharge at various rates

Not all batteries are made alike, as you may have noticed if you’ve kept track of the kind of batteries your various gadgets use and how frequently they appear to deplete when taken out of the charger for an extended period of time. Although self-discharge is a common side effect of all batteries due to their design and the fact that they must go by the physical laws that govern the world, the pace at which they drain varies greatly. These popular rechargeable battery kinds are listed along with how rapidly they discharge.

Charge Type

Monthly Self-Discharge Rate
Lithium-Ion 2-3%
Metal Hydride Nickel (NiMH) 25-30%
Low-Discharge Metal Hydride Nickel 0.25-0.50%
Nickel-Cadmium (Ni-Cad) (Ni-Cad) 15-20%
Lead-Acid 4-6%
The type of batteries that the majority of us use most frequently are lithium-ion batteries. Such batteries are found in a wide range of consumer goods, including drones, action cameras, Bluetooth speakers, tablets, smartphones, smartwatches, and laptop computers. They are the same batteries used in electric cars. These days, portable consumer devices seldom utilise nickel-metal hydride (NiMH) batteries, but power tools typically do since they are less expensive than lithium-ion batteries.

NiMH batteries have a high rate of self-discharge, although there is a variant known as low-discharge NiMH. Small rechargeable batteries are the main application for the discharge rate, which can be as low as 0.25–0.50% each month. The most common type of low-discharge NiMH battery is probably Panasonic’s famous Eneloop series of rechargeable batteries.

NiMH batteries have replaced the earlier Nickel Cadmium (Ni-Cad) batteries, which were the first kind of portable rechargeable batteries. Despite having a higher discharge rate than NiMH, Ni-Cad batteries have a memory effect and require more upkeep than NiMH and lithium-ion batteries, making them less popular nowadays.

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Because of its heavy weight and safety concerns arising from the sulfuric acid bath the lead electrodes are immersed in, lead-acid batteries are not employed in portable electronics. Because of their lead-based construction, lead-acid batteries are unsuitable for use in anything other than stationary applications because even little ones weigh as much as a light dumbbell. The bulk of lead-acid batteries are used in automobile starters, solar-powered off-grid power storage, uninterruptible power supply for computers, and other devices.

Methods for Delaying Battery Self-Discharge

Although you can’t completely stop batteries from draining, there is one easy thing you can do to slow down the pace of discharge for all battery types: keep the batteries cold. Keep the battery as cold as possible if you want to prolong the life of a lithium-ion or NiMH battery.

Cool, naturally, within bounds. Do all you can to minimise heat, but don’t put your batteries in the freezer (condensation difficulties while putting them in and out of the freezer can create major problems with the sophisticated internal circuitry present in current rechargeable batteries).

Instead of putting your power tool batteries out in your hot detached garage, you might want to think about charging and storing them in your cool basement. Additionally, if you won’t be using gadgets for a while, keep them out of hot automobiles and put them in the coolest area of your house.

It’s time to replace your batteries if they are depleting so quickly that you almost have to leave them on the charger all the time to make sure they are ready when you need them. Even with the finest care, batteries deteriorate with time; if a battery can no longer retain a charge as it should, it should be recycled and replaced.