What happens when you overcharge a battery?

Overcharging means charging a battery more than its designed capacity. This process can lead to leaks or irreversible damage and may even cause the explosion of the battery in extreme situations. Overcharged batteries can even cause damage to devices that are connected to them.

What happens when you overcharge a battery

What happens inside a battery when it’s overcharged?

First of all, it’s worth noting that different types of batteries can react differently when they’re overcharged. In this article, we’ll be discussing the Li-ion battery type because it’s the most popular battery that can be found in modern-day devices including smartphones and power banks. 

When a Li-ion battery is overcharged, lithium ions can end up plating onto the anode, which can lead to the formation of small amounts of lithium metal. This can be particularly dangerous because lithium metal is highly reactive and can cause a short circuit within the battery.

Additionally, overcharging can cause the electrolyte in the battery to break down, which can generate extreme heat and potentially lead to a thermal runaway reaction. In a thermal runaway, the heat generated by the breakdown of the electrolyte can cause a further breakdown, leading to a self-sustaining reaction that can result in the battery catching fire or even exploding.

If the battery’s internal temperature rises too high due to overcharging, the electrolyte can break down and produce gas. This can cause the battery to swell or even rupture.

It’s also worth noting that most modern Li-ion batteries have built-in safety features designed to prevent overcharging. These include overcharge protection circuits that will interrupt the charging process if the voltage or temperature gets too high. However, these safety features can fail in some cases, so it’s still important to use the proper charger for your battery and to avoid leaving the battery charging unattended for extended periods of time.

Here’s what overcharging a battery looks like:

Symptoms of overcharged batteries

Sometimes it’s not very easy to tell if a battery is overcharged, especially in the early stages. But after a specific point, symptoms will start to appear. If you notice any of these, your battery might be overcharged and you should take action to prevent further escalation of the overcharging process:

  • Swelling or Bulging: One of the most noticeable physical symptoms of an overcharged Li-ion battery is swelling or bulging of the battery case. This can happen if the battery’s internal pressure rises due to gas production from the breakdown of the electrolyte, which can occur if the battery is overcharged.
  • Heat: An overcharged Li-ion battery may become noticeably warm or even hot to the touch. This is due to the excess energy from overcharging being dissipated as heat.
  • Decreased Performance: Overcharging can lead to a decrease in the battery’s overall performance, which may manifest as a reduction in the length of time the battery can power a device on a single charge.
  • Leakage: In extreme cases, an overcharged Li-ion battery may leak. This can happen if the battery swells and ruptures, allowing the internal electrolyte to leak out. The electrolyte in Li-ion batteries can be harmful, so any leakage should be handled with care.
  • Smoke or Fire: In the most severe cases, overcharging a Li-ion battery can lead to a thermal runaway reaction, which can cause the battery to smoke or even catch fire. This is a serious hazard and can cause damage to the device the battery is in and potentially lead to a larger fire.

What happens when you overcharge a battery? 1

Whenever you see a battery displaying one or more of the above signs, you need to be extra careful. It’s possible that acid spays to be released from the battery. These sprays can cause damage to your eyes, asking, and/or clothes. Contact with overloaded batteries should be avoided as much as possible and they should be approached with great caution.

How much damage can overcharging cause to a battery?

Overcharging is not an ON/OFF process. Instead, it’s like a spectrum of intensity that can have various degrees in terms of consequences. It of course depends on how long and how hard the battery gets overcharged. That means that overcharging can cause just a bit of damage, for example, a loss of capacity, which might even go unnoticed. On the other side, extreme overcharging can lead to complete destruction of the battery, even to fire and in the worst case, explosion. This is why you should treat any overcharged battery like a sitting time bomb in order to avoid any possible accidents. 

Can you repair an overcharged battery?

What happens when you overcharge a battery? 2

Overcharged Li-ion batteries are not repairable and should be immediately replaced. In fact, trying to repair them or ignoring the symptoms altogether can lead to thermal runaway chemical reactions that are extremely dangerous, especially in closed spaces. Instead, when you notice that a battery might be overcharged, please disconnect it from the power source immediately and place it in a safe, non-flammable container. Then dispose of it as soon as possible in a dedicated collection spot. 

What should you do in case of an overcharged battery?

First of all, try to prevent an overcharge from happening. Always have a look at the battery charger you are using and at the device you’re charging. Make sure to use the correct voltage when recharging your battery and not leave it charging for long periods of time.

However, if you do manage to get a battery to overcharge try to immediately replace the battery as soon as possible. There is not really a thing you can do. Ideally, dispose of the overcharged battery at designated collection points. Under no circumstances should you dispose of the battery in a regular trash bin as it could generate fires and also because it’s very bad for the environment.

Why rechargeable batteries should be constantly recharged

Brand new batteries sold on the shelves come with a full charge but they are slowly discharging. Given enough time, all batteries will deplete completely if not recharged. So overall, any battery requires two cycles to ensure a long service life: charging, and discharging. If the battery is left for too long without any of these two processes, its lifespan will be affected.

In order to make sure your battery will perform for long periods of time, try not to let it deplete under 10% on a regular basis. From time to time, it’s ok to fully deplete it. But if this is done regularly, then its lifespan will be shortened significantly. Keeping an eye on this single factor might a considerable amount of time to the expected battery lifespan. 

Overcharging in car batteries

Car batteries that are found in modern cars can also suffer from overcharging, even though they have a different type of build. They are in fact lead-acid batteries. When a car battery is overcharged, the electrolyte (a mixture of sulfuric acid and water) can be electrolyzed, creating hydrogen and oxygen gases. Overcharging can lead to the breakdown of the lead and lead dioxide in the car battery, causing permanent damage.

In addition, an overcharged car battery will often become noticeably warm or even hot to the touch. Other signs of overcharging can include an acidic or rotten egg smell (due to the release of hydrogen sulfide gas), visual swelling or deformation of the battery case, and in severe cases, leakage of the acidic electrolyte.

Have you ever encountered an overcharged battery? Let us know in the comments!

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