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What is overdischarging in batteries?

What is overdischarging in batteries?

The term “Overdischarge” refers to a situation in which a battery’s voltage falls below the minimal level. In this article, we’ll discuss overdischarge and answer any questions you may have about it. So, without further ado, let’s get started.

What happens if the lithium battery is overdischarged?

According to a paper published in the Journal of The Electrochemical Society titled Overdischarge and Aging Analytics of Li-Ion Cells, due to the decomposition of the solid electrolyte interface (SEI) layer and the gases produced from it, overdischarge causes swelling in Li-ion pouch cells.

This is a relatively common problem with lithium-ion batteries, but it can also occur with overcharged batteries. It’s worth noting that the electrolyte decomposition of lithium-ion battery anode materials results in the formation of a passivation layer known as the solid electrolyte interface (SEI). Lithium-ion batteries’ cycles, rate capacity, irreversible capacity loss, and safety all depend on the SEI’s quality.

Due to the fact that overdischarged batteries swell, they become extremely dangerous at this point, and you should avoid applying pressure or puncturing them because the battery has a very high risk of catching fire or perhaps exploding.

Each time a lithium-ion battery is overdischarged, its capacity is dramatically reduced, which is one of these batteries’ downsides. Therefore, to avoid the negative consequences of overdischarging, keep them charged to at least 20%.

As previously stated, overdischarge happens when a cell is discharged over the minimum safe voltage limit specified by the electrode chemistry coupling. This is a pretty regular occurrence with battery packs. Compared to single cells, battery packs have the potential for overdischarge since all cells are depleted at a similar rate, regardless of their capacity.

For example, consider three lithium-ion batteries: two that are completely charged and one that is 50% charged (SOC). In this case, the partially discharged cell will be fully discharged before the other two and, if kept on, will be driven into voltage reversal by the other cells if the load is not removed. Eventually, the discharged battery will stop functioning and will most likely swell in the near future.

How do you fix an overdischarged lithium battery?

Although it is possible to restore overdischarged batteries, this is not recommended due to the significant loss of performance that occurs as a result of doing so. Apart from performance, overdischarged batteries pose a safety risk due to their unstable state. As a result, efforts to revive them may result in tragedy.

When lithium-ion batteries stop operating due to a lack of charge, this does not always mean they are permanently dead. Rather than that, they go into “sleep mode” when their voltage falls significantly and remains low for an extended period of time. The dead lithium-ion battery can be resurrected in this state. If you’ve made up your mind and want to revive the dead battery, we’ll explain how.

There are two methods for reviving a dead lithium-ion battery: one is to use a charger with a “Boost”, “Recovery”, or “Wake Up” feature, and the other is to follow the steps below. To begin, we’ll show how to resurrect a dead lithium-ion battery using a multimeter, crocodile clips, and a healthy battery.

Method 1: utilizing a healthy battery to revive the dead lithium-ion battery

Step 1: Connect a healthy battery to the dead battery

  • Take a healthy battery with the same voltage as the dead cell and connect them in parallel to revive the battery. 
  • Next, connect the two batteries in parallel using the crocodile clips.
  • At this point, connect the negative terminals together and then the positive terminals. To avoid a short, make sure the wires don’t cross one other.
  • Allow the batteries to remain in this position for around 15 minutes while you watch the process, keeping an eye out for any signals of potential danger, such as overheating. 
  • Now, you should observe an increase in the voltage of the dead lithium-ion battery as it prepares to charge using a voltage reader.

Step 2: Charging and discharging the battery

  • The following step is to charge the battery using the lithium-ion charger fully.
  • After recharging the battery, it’s time to drain it completely but not to the point where the voltage drops below the designed level.

Step 3: Freeze and defrost

  • Place the battery in the freezer, but first seal it in an airtight plastic bag; otherwise, moisture will further deteriorate the battery.
  • Next, remove the battery from the freezer after 24 hours and allow it to defrost until it reaches room temperature.

Step 4: Charge the battery again

  • Once the battery has cooled to room temperature, insert it into the lithium-ion battery charger and charge it 100%.
  • This restores the majority of the battery’s capacity lost during the overdischarge process.

Method 2: A charger with Boost feature

If you want to revive a battery more quickly and safely, or if you lack the required tools such as a multimeter, crocodile clips, and a healthy battery, we recommend purchasing a charger that has “Boost,” “Recovery,” or “Wake Up” features. 3.

Step 1: Purchase a charger equipped with the Boost feature

  • After purchasing the charger, read the user manual completely to become familiar with how the Boost function works. To finish the process, they frequently specify how long the battery should be in boost mode.
  • After that, carefully insert the battery and follow the user manual’s instructions.

Step 2: Charging and discharging the battery

  • Once the boost procedure is complete, it’s time to charge the battery.
  • Bear in mind that, depending on the charger type, some will begin the normal charge immediately once the boost is complete, while others will not.
  • After fully charging the battery, place it in a device that rapidly drains it (such as a flashlight) and turn it on to completely drain it.

Step 3: Freeze and defrost

  • As with the first method, place the battery in an airtight plastic bag and freeze it for 24 hours.
  • Remove it from the freezer after 24 hours and let 8 hours for it to defrost to room temperature.
  • Now is the time to charge the battery for the last time.

How to prevent batteries from overdischarging?

Typically, overdischarging occurs with batteries in equipment we do not use on a regular basis, such as drones. Therefore, after utilizing drones, ensure that they are not returned to their box with no charge remaining. At the very least, attempt to charge them to 20%; otherwise, the battery will die or its capacity will considerably decrease.

Take note that the majority of lithium-ion batteries sold nowadays have overdischarge protection. Over-discharge protection is designed to shut off the circuit when a predetermined voltage threshold is reached.

However, due to poor quality construction or lack of these features, certain batteries fail to protect against overdischarge. As a result, we recommend getting batteries from reputable companies. If you’re interested in learning more about this feature, check out this article: What is over-discharge protection in power banks? 

Conclusion

While lithium-ion batteries have several benefits over other types of batteries, they have a few disadvantages, including overcharging and overdischarging. Although these drawbacks have been solved in recent years with intelligent circuits; yet, you should take care of them by purchasing chargers with safe charging protections and following correct charging habits.

 

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