What Happens to an Unused Battery Over Time?

There is a pretty good chance that you have some kind of battery just laying around and not being used for a long time. If so, you might wondering what happens to an unused battery over time? I will explain it to you how different types of batteries behaves, and whether they will degrades over time and what you can do about it. So, let’s see the correct answer for this question.

All batteries will degrade over time if not used, period. And depending on the battery type it will degrade in faster or slower rate. They degrade because of physical and chemical mechanism that occurs inside them. This mechanisms depends on battery chemistry, fabrication, operation condition, usage history and so on. In some of the batteries we can’t do anything to stop or slow down degradation, but in others we can actually slow down degradation process and get some more energy life.

We have a couple of battery types, and they are divided into two groups. First group are Primary cells or non-rechargeable batteries and second group are Secondary cells or rechargeable batteries. Most common ones of both of the groups are:

  • Nickel Cadmium (NiCd)
  • Nickel-Metal Hydride (NiMH)
  • Lead-Acid
  • Lithium Ion (Li‑ion)
  • Lithium Ion Polymer

There is a many more types of batteries. They are not quite known because of their impractical applications. In other words they are not useful, but they still exists. Some of them scientists use to future develop a new class of batteries.
So, let’s see what will happens to an unused batteries of common types that we listed above.

Primary cells (non-rechargeable) batteries

This group of batteries like all the other once will lose their charge over period of time. After 3 to 4 years most major brand names disposable alkaline batteries will have most of their initial charge.

But if we compare Lithium based batteries to alkaline, Lithium based primary cell batteries will last longer. Any self discharge of this primary cell batteries are permanent, because they can not be recharge. So, do unused batteries expire?

One tip that I have for you is that if you buy this primary cell batteries take a close look on expiration date, and you can check it on a package, it is printed there.

Lead-acid batteries

How long do unused car batteries last? For Lead-acid batteries, we know that monthly charge loss at 20°C is about 2-8%, and this percentage doubles for every 10°C increase in temperature.

That will be something like this, If the Lead-acid battery stays 4 years at 20°C and never be recharged it will only have 10% of its charge. Let’s just say that if the Lead-acid battery stays in discharged state for that much time, it will have damage that is permanent trough multiple physical and chemical mechanisms, which will form a non-conductive lead sulfate on the plates.

We also have Lead-acid batteries which are flooded, and they will lose water over time by evaporation. So, if you want to store that battery well in addition to charging it every 6 months you will also need to add water into the battery cells.

This maintenance should be regular every 6 months or so, in order for battery to  last long time, more than just 3 to 4 years. But probably will lose some capacity, and that is pretty normal for Lead-acid batteries.

Nickel-metal hydride (NiMH) and nickel-cadmium (NiCd)

Nickel-metal hydride (NiMH) and nickel-cadmium (NiCd) batteries lose 20% per month of its charge, and that’s the old and bad design.

Newer development of this batteries are greatly improved, and that really bad discharge rate of 20% is reduced to amazing 2-3%. And this batteries have long battery shelf life in its discharged state.

Only concern is that Nickel-metal hydride (NiMH) and nickel-cadmium (NiCd) batteries will lose electrolyte through evaporation, and because they are sealed really well this process will take a long time.

The permanent damage of this batteries that I can think of will be for example if you store them in multi-cell environment with an attached electrical load on them, one or more cells will reverse its  polarity and cause a failure.

In contrast to this, if you have new, unused battery and you store them in discharged state it will be fine for long time and you should not worry, when you recharge them it will be perfectly fine.

Lithium Ion (Li‑ion) and Lithium Ion Polymer

This batteries after storing them for a long time will be just fine, because they have very low self discharge rate. But, even then they have some loses over time, especially if you store them fully charged you can notice that some of capacity is lost.

Lithium Ion batteries can also be permanent damaged. For example, some of them have monitoring circuitry built in, and this feature will consume battery stored energy charge.

And if the Lithium Ion battery is deeply discharged you can called a day and toss that battery out. To reduce degradation of Li-Ion batteries it is recommended to store them at about 50% charged state just in case of self discharging.

If you’re a drone pilot you know that Lithium Polymer drone batteries are most common batteries for drones. This LiPo batteries also belongs to the group of Lithium Ion batteries and the same rules apply.

Lower Temperature Battery Storing

If you want to improve life of a battery while storing them you should do it at a low temperature. I know what you think right now, refrigerators, right? But, that is not recommended at all, because when time comes to get the battery out from a refrigerator it will form a condensation.

And you already know that water and electricity shouldn’t be mixed at any costs. If the battery gets wet while storage, obviously the rate of discharge will be increased since the wet surface of the battery can form a conductive path between the terminals and cause a closed loop which leads to a faster self discharge.

Freezing can also damage water-based batteries, all but lithium-ion, due to expansion of the electrolyte, causing anode and cathode to potentially crack and gets in open or closed circuit.

Did you ever heard of nanocrystals?

Scientists discover the reason why batteries lose capacity over time, and it’s a single word: Nanocrystals!

When scientist develop a new batteries, what we usually get it is just an overall capacity. And repeated charging cycles stay the same or slightly better, but that is so tiny success that is not noticeable at all.

And capacity is nothing without the longevity to survive a large number of repeated charging cycles. The most advanced Li-Ion battery suffers from losing capacity as they get older.

Until we know the cause why this is happening we can not prevent that. The new studies from the US Department of Energy come across some evidence.

They saw that tiny nanoscale crystals are guilt for capacity loss over time.

The team from Brookhaven National Laboratory used a very sensitive transmission electron microscope (TEM) to observe the changes in high-quality nickel-oxide anodes as they were repeatedly charged and discharged.

They saw that as lithium ions pass through cathodes and anodes, they become stuck between ion channels which was caused by  reaction and small crystals are made, this is buildup of salt.

This cause to move less efficient and lower their capacity.

The conclusion here is that component there are used for anode and cathode are not perfect. Materials of which are anode and cathode made have imperfections no matter how they are carefully made, so causing this crystals to form.

The second study from the Department of Energy’s National Renewable Energy Laboratory looked at the effects of charge speed and capacity on batteries. They get more attention to cathode.

In fact what they are realise is that if they want to get more of the battery density, the longevity will be hurt here. The more density, the nanocrystals will form faster.

So, is there a way to prevent this nanocrystals to form? It may be. In theory they should treat the battery components with a type of atomic deposition to fill in the  tiny gaps and imperfections as possible with nanoparticles.

This way will slow down formation of crystals in the ion channels. That will obviously not solve the problem but will make possible for scientists to create much more density without hurting longevity.

We are facing many devices with non removable battery, which can be so stressful because lifetime of a devices are determined by how many cycles battery can take, and yet companies making smartphones, tablets and laptops with non removable batteries. And this is not good.

This research might open new doors in battery development, and as we can see the  battery longevity is more important then battery density or capacity.

By figuring out how to fix this not quite simple problem your battery can last long long time without need of replacing it. With future development scientist will solve this problem once for good, I am sure.