How to Restore NiCad Batteries

Nickel-cadmium, or NiCad, batteries are a common type of battery. Although lithium-ion batteries are becoming more popular, you likely have a battery-powered tool or appliance that uses NiCad batteries. The rechargeable AA and AAA batteries in your solar lights or flashlights may be NiCad. Unfortunately, NiCad batteries have a problem with the “memory effect.” This is especially a problem in older NiCad batteries. The battery builds up “memory” based on a short charging cycle, and it can no longer charge to its full capacity. Thankfully, there are solutions to this! Keep reading to learn NiCad battery essentials and how to restore NiCad batteries.

NiCad batteries are rechargeable batteries that use nickel oxide hydroxide and metallic cadmium as electrodes. The name NiCad is broken down into two parts. The Ni comes from the chemical symbol of nickel (Ni), and “Cad” comes from the chemical symbol of cadmium (Cd).

The first NiCad batteries were invented in 1899. Since then, they have been greatly improved and modified. They were once widely used in portable power tools, flashlights, and other portable electronic devices.

Why Do NiCd Batteries Fail?

NiCad batteries can fail for a variety of reasons. The most common one is the “memory effect.” A NiCad battery can build up memory based on how it’s charged. For example, if you discharge a NiCad battery to 50% and then charge it, over time, the battery will begin to register 50% as 0. Once this memory is established, the battery will no longer use the other 50% of its charge.

They can also fail due to frequent overcharging, leaving the battery discharged for a long time, or exposure to extreme temperatures. You can tell this is happening to a NiCad battery when it appears to be fully charged but discharges quickly after a short period of use.

How to Restore NiCad Batteries?

If your NiCad batteries are refusing to charge, you might be wondering what to do with them. Do you throw them in the trash? Or take them to a recycling facility?

Luckily, there is a third option. You can bring your NiCad batteries back to life! Let’s take a look at how to restore NiCad batteries in several different ways.

By Freezing

The first method for reviving NiCad batteries is freezing them. First, take the battery out of whatever electronic device it is powering. Next, put the battery in a plastic bag and carefully seal it. Clean and dry the battery before placing it in the bag.

Place the battery in the freezer and leave it for 24 hours. After 24 hours have passed, remove the battery from the freezer and let it thaw. You should allow the battery to thaw at room temperature for 5–6 hours.

Finally, remove the battery from the bag and clean off any water or moisture accumulated on the battery.

By Discharging

Another way of reviving a NiCad battery is by completely discharging it. Completely discharging a NiCad battery is particularly important because of its ability to build up memory.

The first step of this process is to use the battery until it is completely discharged. Then, charge the battery with a high-quality charger until it is fully charged.
Repeat this process three to four times and then check the performance of the battery. This process should erase any memory the battery has.

Safety Tips & Warnings When Reconditioning NiCad Batteries

Reviving NiCad batteries can be dangerous. Wear goggles and gloves for safety at all times when restoring a NiCad battery. Additionally, check the battery voltage before attempting to revive a NiCad battery. It is essential to take the appropriate safety measures when refurbishing a NiCad battery.

Tips to Maintain NiCad Batteries

Now that you have reconditioned your battery, the proper care will ensure that it remains in tip-top shape. The first time you use the revived battery, discharge it completely and then charge it fully. Charge the battery only when it’s fully discharged to keep it operating at its full capacity.

After a NiCad battery has been fully charged, do not leave it in the charger.Getting a charger that shuts off automatically when the battery is charged is highly recommended. If you do not have one, pay attention to the LED indicator on the charger and remove the battery as soon as it indicates that it’s fully charged.

FAQs

You might have some questions as you are figuring out how to restore NiCad batteries. These are the most common ones you’ll likely have.

Can You Revive NiCad Batteries?

You can revive NiCad batteries. It is possible to remove the memory they build up using the methods listed above. However, even after restoring the battery, it may not have the same charging capacity as when it was brand new. Maintaining your NiCad batteries is the first and best option.

How to Tell if a NiCad Battery is Bad?

It is relatively easy to see if a NiCad battery is bad. You can accomplish this in two steps.

The first way is to do a basic voltage check. Take a multimeter set to direct current voltage. Take the red multimeter probe and touch it to the positive end of the battery, and the black multimeter probe to the battery’s negative terminal. The multimeter will display a voltage. If the number is 10% or less of the initial rating, the battery can’t be used.

The next step is testing milliampere hours. First, connect the battery to a circuit that will discharge the battery. Any device that uses a battery is sufficient (i.e., flashlights, toys, radios, etc.). Charge the battery completely before testing it.

Occasionally remove the battery from the circuit and test the battery voltage as described above until the voltage per cell drops to one. Calculate how long it took (in minutes) for the battery to discharge. Multiply the time by the current (in milliamperes) and divide the result by 60 to get the battery capacity in milliampere-hours (mAh).

Compare this number to the battery’s rating. A mAh rating lower than what the battery is rated for indicates that the battery needs to be revived.

How Long Does a NiCd Battery Last?

If properly maintained, NiCad batteries can last up to 15-20 years. If you are using the battery regularly, a NiCad battery can last for around 1,000 cycles of discharging and charging if appropriately used.

Do NiCad Batteries Have a Memory?

If misused, NiCad batteries can build a memory. You can reset this memory using the methods described earlier in the article.

How to Dispose of NiCad Batteries?

Do not throw your batteries away. Batteries are toxic and can harm the environment if they are disposed of improperly. All batteries, including NiCads, should be recycled by an authorized facility.

Which Is Better, NiMH or NiCad Battery?

NiMH batteries have more capacity than NiCad batteries, which means they can power a device for longer. Additionally, modern NiMH batteries do not suffer from the memory effect that NiCad batteries do. Finally, NiMH batteries are better for the environment.
However, NiCad batteries are cheaper and perform better in extreme temperatures.

The Takeaway

Even as new battery options become available, NiCad batteries are still going strong. Testing and reviving older NiCad batteries is a great way to save money and protect the environment. With the proper care, your NiCad batteries can keep your electronics running well into the future.
Wondering what the main differences between NiCad, NiMH, and Lithium-ion are? Find out here.
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