Common Parameters Of Rechargeable Batteries

Battery capacity represents how much electrical energy a battery can store. The number we see on the battery packaging usually indicates the battery capacity. It is expressed in ampere-hours (Ah) or milliampere-hours (mAh). It is a composite unit, composed of the product of a unit of current and a unit of time, representing the battery's ability to continuously discharge under a constant current. A fully charged battery can be discharged for 10 hours at 200mA. Multiplying the current by the time gives us the battery's capacity as 2000mA.H. If it is discharged at 400mA, it will last for 5 hours.

Energy density: The amount of electrical energy contained per unit volume or unit weight. For the same amount of electrical energy required, a battery with higher energy density can be smaller and lighter.

C-current: The current required to completely discharge a fully charged battery or fully charge a depleted battery within one hour. It is essentially the numerical value of the ampere-hour capacity. A battery with a capacity of 1800mA has a C-current of 1800mA. A battery with a capacity of 2000mA has a C-current of 2000mA.

Open-circuit voltage: The potential difference between the two terminals of a battery.

Memory effect: In a new battery, the electrode material has fine grains, maximizing the electrode surface area. However, due to use, crystallization occurs within the battery's contents. This crystallization leads to grain enlargement, also known as passivation, reducing the usable electrode area. Furthermore, the enlarged grains increase self-discharge, reducing battery capacity and impairing performance. This is the memory effect. The memory effect occurs due to repeated partial charging and discharging of the battery.

Self-discharge rate: Even when not in use, a charged battery gradually loses charge. Generally, the higher the temperature, the more significant the self-discharge.