As opposed to traditional flooded batteries, valve-regulated maintenance-free lead-acid batteries do not require maintenance. VRLA’s are sealed to prevent any acid leakage or dissipation. In addition, one-way safety valves automatically release excess gases if pressure exceeds safety limits. This allows the battery to maintain healthy pressure levels without outside support.
According to the technology, there are two kinds of lead-acid batteries: general type (AGM) and GEL. AGM battery uses glass fiber cotton (Absorbed Glass MAT) as a separator, and liquid electrolyte (the electrolyte is absorbed on plate and separator, and cannot flow in the battery). The GEL battery has silica as a solidifier and the electrolyte is adsorbed on the plate as colloid.
Accordingly, to using purpose, they also can be mainly divided by usage: starting batteries, stationary battery, and traction type, etc.
In the conditions of the stipulated design (such as temperature, discharge rate, and final voltage, etc.), the rated capacity means the battery should be able to release the lowest capacity, the unit is ampere-hour, expressed as a symbol of C. Capacity is strongly influenced by the discharge rate, so we often show the discharge rate by Arabic numerals at the lower right corner of the letter "C", such as C20=50Ah, it means that under the condition of 20-hour rate to discharge to the final voltage, the capacity is 50 ampere hours. Informally, the rated capacity of 50 ampere hour of battery in full charge of state, the battery can be discharged for 50 hours with 1 A of current.
Open-circuit voltage (OCV) refers to a battery that is disconnected from any circuits and has no external currents flowing between terminals. An electric meter measures the voltage between the two terminals; and though the OCV cannot be utilized as a standard to measure battery voltage, the differences in electrical potential can be compared to one another to determine the state of the charged battery.
End of discharge voltage is the allowable minimum voltage of battery discharging. When the battery voltage is lower than the EOD, the voltage of the battery will drop rapidly if discharged continuously, and it will over-discharge the battery. This may result in permanent damage to the battery.
The EOD is connected with discharge rate, and discharge current affects the EOD voltage directly. Under the stated end of discharge voltage, the greater the discharge current, the smaller capacity of the battery.
When the battery is fully charged, the active materials of the lead plates have reached saturation; the battery voltage will not increase, even with additional charging.
During battery use, the battery capacity will discharge a percentage of it rated capacity. This is called depth of discharge (DOD); DOD at 60% means the discharged capacity of the battery has reached 60%, and 40% of its capacity remains.
Cycling use: The battery is used as a direct power supply for equipment, which mainly applies to the circulation charge and discharge of electrical equipment.
Float use: The battery is used as an emergency power supply for equipment to provide emergency power or energy storage in the event of a power outage (ex: power plant, UPS power supply, emergency lighting, etc.).
The main methods of battery charging are constant-current charging, constant-voltage charging, constant-current with limited voltage charging, equalizing charging, float charging, and pulse charging.
Float charging: A battery powered by a circuit in the event that the normal power supply is interrupted. The terminal is always connected to a constant-voltage power supply to maintain the battery’s charge.
Equalizing charging: It is a deliberate overcharge to ensure that each cell of the battery is equally charged.
The purposes are listed below:
① The battery charge is insufficient or the initial charge was interrupted;
② The battery was consistently undercharged;
③ Failure to charge timely after discharge;
④ Frequent over-discharging or over-charging;
⑤ The density of electrolytes or high temperatures-lead sulfate is formed and not easy to eliminate;
⑥ The battery was stored away for long periods of time without being regularly charged;
⑦ Impure electrolytes, which caused rapid self-discharge.
Proper storage requires an environment with stable flooring, good ventilation, dry conditions, and lower temperatures (around 15- 25 degrees Celsius). Even when in storage, the battery should be charged every 3-6 months.