Some Basic Elements of 18650 Battery

The 18650 rechargeable battery is a crucial component of many solar lights. Selecting an appropriate 18650 battery is especially important for the lifetime of your solar light.

What is 18650 battery?

The term 18650 refers to the battery’s design specifications. “18” signifies that the diameter of the battery is 18 mm, “65” specifies that the length is 65 mm, and “0” signifies that the battery is cylindrical in shape.

Types of 18650 Batteries

Batteries may be categorised based on the following factors:

  • Shell Material: This includes aluminum shell lithium batteries, steel shell lithium batteries, and soft pack batteries.
  • Cathode Material: The cathode materials may vary and include lithium cobaltate (LiCoO2), lithium manganate (LiMn2O4), ternary lithium (LiNixCoyMnzO2), and lithium iron phosphate (LiFePO4).
  • Electrolyte State: Batteries are divided into lithium-ion batteries (LIB) and polymer batteries (PLB) based on the state of the electrolyte.
  • Usage: Batteries can be categorised into ordinary and power batteries.
  • Performance Characteristics: This includes high-capacity batteries, high-rate batteries, batteries designed for high temperatures, and batteries designed for low temperatures.

Some Important Parameters

The following are several key parameters to consider when selecting 18650 rechargeable batteries..

1, Capacity (mAh)

Capacity represents the amount of power a battery can provide under specific discharge conditions. The formula to determine this amount is Q=I x t, measured in coulombs. Battery capacity is typically denoted in Ah (ampere hour) or mAh (milliampere hour). This means that a 1 Ah battery is capable of discharging for 1 hour at a rate of a 1 A when fully charged.

2, Charge/Discharge Rate

The charge or discharge rate indicates the current at which the battery is being charged or discharged, often measured in multiples of the battery’s nominal capacity. For example, if a battery has a capacity of 1500 mAh, it is stipulated that 1 C=1500 mAh. If discharged at a 2 C rate, the battery is discharging at a current of 3000 mA, while a 0.1 C rate equates to a charge or discharge current of 150 mA.

3, Open Circuit Voltage

The open circuit voltage refers to the potential difference between the positive and negative terminals of the battery when no current remains in the circuit. This term is often used to denote the nominal or rated voltage of a lithium battery. The standard nominal voltage for regular lithium batteries is typically 3.7 V, which is also referred to as the voltage platform.

4,Cut-Off Voltage

The cut-off voltage is further divided into the charge cut-off voltage and the discharge cut-off voltage. Essentially, these signify the voltage levels at which the battery can no longer be charged or discharged. Persisting to charge or discharge a battery at the cut-off voltage can significantly affect its lifespan. For a lithium-ion battery, the typical charging termination voltage is generally 4.2 V, while the discharging termination voltage is 3.0 V.

5, Internal Resistance

Internal resistance refers to the resistance a battery offers to the flow of current during operation. Generally, a battery’s internal resistance consists of ohmic internal resistance and polarization internal resistance. Factors that affect the value of internal resistance include the battery’s material, manufacturing process, and structure.

6, Cycle Life

A battery’s cycle life is an important measure of its lifespan and is defined by a single instance of charging and discharging. To illustrate, according to IEC standards for a cell phone lithium-ion battery, a 0.2 C discharge to 3.0 V is followed by a 1 C charge to 4.2 V. After 500 repeated cycles, the battery’s capacity should remain at least 60% of its initial capacity. Thus, the cycle life of a lithium-ion battery is considered to be 500 cycles.

7, Self-Discharge Rate

This refers to the speed at which the battery’s capacity decreases during storage. It is expressed as a percentage decrease in capacity over a specific period of time. The standard self-discharge rate for a lithium battery ranges from 2% to 9% per month.

8, Internal Pressure

Internal pressure refers to the air pressure inside the battery. This is caused by the gases produced during the battery’s charging and discharging process.

Charge-discharge Curve of Battery

charge curves of 18650
discharge curves
18650 discharge curves

Some Essential Protections

We use safe, rechargeable batteries to ensure the reliable performance of solar lights.

1, Batteries are protected against overcharging and over-discharging.

High-quality 18650 rechargeable batteries come equipped with quadruple protection:

  • Short-circuit protection
  • Overcurrent protection
  • Overvoltage protection
  • Battery reverse connection protection

2, Batteries feature an explosion-proof valve.

In order to prevent the sealed metal case from exploding, 18650 batteries are equipped with a safety valve on top. If the pressure inside the battery becomes too high, the top safety valve will open to vent and depressurize the battery, thus preventing an explosion. This safety valve is a standard feature of every 18650 battery and is the primary safeguard against explosions.

18650 safety valve

LayviKay Only Use High Quality 18650 Rechargeable Batteries

We use high-quality batteries in our solar pillar lights, which are UL/CE/KC/CB/MSDS certified. Every batch of these batteries is sampled and tested for various parameters. We ensure that after 500 cycles of charging and discharging, the storage capacity of the battery is still greater than 80% of its initial capacity.

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