The Ultimate Guide to 18650 Battery Problem

The Ultimate Guide to 18650 Battery Problem

What is an 18650 battery

The 18650 battery is a lithium-ion battery, and its name comes from its size: diameter: 18mm, height: 65mm. The voltage of the 18650 battery is 3.6V, and the capacity is between 2200mAh and 3600mAh. 18650 batteries are often used in flashlights, laptop computers, electronics and even electric vehicles because of their high reliability, high energy density, and hundreds of charge and discharge cycles.

How does the 18650 battery work

The working principle of lithium-ion battery refers to its charging and discharging principle.

Lithium-ion battery charging principle

When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte. As the carbon layer structure of the negative electrode, it has many micropores, and the lithium ions that reach the negative electrode are embedded in the micropores of the carbon layer. The more lithium ions are embedded, the closer to the fully charged state.

Lithium-ion battery discharge principle

The lithium ions embedded in the carbon layer come out and move back to the positive electrode. The more lithium ions returned to the positive electrode, the higher the discharge capacity. The battery capacity we usually refer to refers to the discharge capacity.

Charging process

Lithium battery charging is generally divided into two stages. When the battery voltage is lower than 4.2V, the charger will charge with a constant current. The second stage is the constant voltage charging stage. When the battery voltage reaches 4.2V, due to the characteristics of lithium batteries, if the battery voltage is higher, the battery will be damaged. The charger will fix the voltage at 4.2V, and the charging current will gradually decrease. When the current decreases to a certain value, the charging circuit will be cut off, and the charging is completed.

Some chargers are implemented with cheap solutions, and the control accuracy is not good enough, which may easily cause abnormal charging of the battery and even damage the battery. When purchasing a charger, try to choose a big brand 18650 lithium-ion battery charger. The quality and after-sales are guaranteed to prolong the service life of the battery.

Application field of 18650 rechargeable battery

18650 batteries are widely used in various devices due to their light weight and high energy density. Portable devices such as laptops, digital cameras, tablets, flashlights, and e-cigarettes often use 18650 batteries. 18650 batteries are also mainly used in power tools such as drills, saws, trimmers, grinders. More recently, the batteries have also been used in electric cars, hybrid cars, electric bicycles and electric wheelchairs, as well as in solar systems and drones. Even the Mars Curiosity rover uses 18650 batteries. 18650 batteries are also commonly found in solar lights and are used as energy storage devices.

18650 battery life

Most 18650 batteries have a lifespan of 500 charge cycles (Charging cycle: Fully charged and then used up as a cycle). For example, Olight batteries are rated for 500 cycles, which means that the battery capacity is generally only 80% of its initial capacity after 500 cycles, and once this value is reached, the battery life is over. While you can still use it, the battery capacity will continue to drop over time.

How long does it take to fully charge an 18650 battery

It takes about 4 hours to fully charge the 18650 battery in most cases. Of course, this depends on the battery health and charger charge rate.

Reasons why 18650 lithium-ion battery loses vitality

In most cases, the voltage of a fully charged 18650 Li-ion battery is about 4.2V, and the voltage after discharge is about 3.0V. After a deep discharge, the voltage will drop below 2.5V, most Li-Ion battery chargers cannot be used to charge deeply discharged batteries. This is because the charger needs to detect if the battery is a rechargeable battery, to avoid charging a non-rechargeable battery, which could cause a fire.

How to fix a lithium ion battery that won't charge

What you need to do is to provide enough power for the battery to make the battery voltage rise above 2.5V, at this time the battery can be charged normally.
1. Some chargers have a boost function to charge a deeply discharged battery, which is the easier way.
2. The second method, first, you need to connect the battery to a 3.0V-5.0V power supply, after charging for about 5 minutes, the voltage can be increased, and then you can put it in the charger to charge. (You should Always present, overcharging the battery can cause a fire)

(The battery voltage after deep discharge is 0.423V, and the charger can no longer charge it)

Set the DC power supply to 5V and prepare to connect the Li-Ion battery.

Connecting the Li-ion battery

After about 5 minutes, re-measure the battery voltage, you can see, the battery voltage is 3.367V, in fact, as long as the battery voltage is more than 2.5V, you can put it in the battery charger.

Now I can put them in my fast charger and charge them fully.

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