Battery operating characteristics

1. A valve-regulated sealed lead-acid battery consists of positive and negative plates, separators, electrolyte, a safety valve, and an outer casing. This type of battery is known as a "cathode absorption" design, where the amount of active material on the negative plate is approximately 15% greater than that on the positive plate. During charging, the positive electrode becomes fully charged first, while the negative electrode only reaches about 90% of its capacity. As a result, under normal operating conditions, oxygen is produced at the positive electrode, while hydrogen generation at the negative electrode is minimal and easily recombined. This design helps reduce gas emissions and makes the battery maintenance-free.

2. Key performance indicators for batteries include electromotive force (EMF), internal resistance, final voltage, discharge rate, charge rate, and cycle life.

(1) Electromotive Force (EMF): This refers to the voltage generated by the battery when it is not connected to any load. It represents the potential difference between the two electrodes.

(2) Internal Resistance (r): The internal resistance of a battery affects its efficiency and performance. A lower internal resistance means better power delivery and less energy loss during operation.

(3) Final Voltage: This is the voltage at which the battery stops discharging due to a sharp drop in terminal voltage. Continuing to discharge beyond this point can damage the battery. The final voltage varies depending on the discharge rate. For example, the formula for calculating final voltage is: **U_final = 1.66 + 0.0175 × h**, where **h** is the discharge hour rate. At a 1-hour discharge rate, U_final = 1.66 + 0.0175 × 1 = 1.68 V. At a 10-hour rate, U_final = 1.66 + 0.0175 × 10 = 1.835 V.

(4) Discharge Rate: This is the rate at which a battery discharges to its final voltage under specific conditions. It is usually expressed in terms of time or current. A common standard is the 10-hour discharge rate, meaning the battery should be discharged to its final voltage within 10 hours. The battery’s capacity depends on the discharge rate—lower rates typically yield higher capacities.

(5) Charge Rate: This refers to the rate at which a battery is charged under certain conditions. The most commonly used charge rate is the 10-hour rate, where the battery is fully charged in 10 hours. If the charge time is reduced, the charging current must be increased, and vice versa.

(6) Cycle Life: This is the number of complete charge and discharge cycles a battery can undergo before its capacity drops below a specified level. A longer cycle life indicates better durability and performance over time.