Supports

Charging Methods

Correct charging is one of the most important factors to consider when using valve regulated lead acid batteries. Battery performance and service life will be directly affected by the charging methods.

There are two major methods of charging:

• Constant voltage charging
• Constant current charging

Constant Voltage Charging

This is the recommended method of charging for VRLA batteries. It is necessary to closely control the actual voltage to ensure that it is with the limits advised.

Standby Use:

2.23-2.30 vpc at 20oC(68oF) to 25oC(77oF)

Cycle service:

2.40-2.50 vpc at 20oC(68oF) to 25oC(77oF)

It is suggested that the initial current be set within 0.3CAmps. Figure 5 and 6 indicate the time taken to fully recharge the battery. It is also seen that the charging current is decreased to approx 0.5-4mA/Ah under charging voltage 2.30 vpc, and 3-10mA/Ah under charging voltage 2.40vpc when the battery is fully charged at 20oC(68oF) to 25oC(77oF).

Note: it is necessary to ensure that the voltage is correctly set. The charging voltage set too high will increase the corrosion of the positive plates causing loss of capacity and ultimately shortening the life of the battery.

Constant Current Charging

This method of charging is generally not recommended for VRLA batteries. It is necessary to understand that if the batteries are not removed from the charger as soon as possible after reaching a state of full charge. Considerable damage will occur to the batteries due to overcharging. The required recharged capacity is 1.07 to 1.15 times as discharged capacity.

Charging Time

The time required to complete each charge depends on the discharge condition of battery, characteristics of charge used, or the temperature during charge. For cyclic use, using constant voltage charging, this time can be estimated by the following expression at 25oC/77oF.

(1)Discharge current: Larger than 0.25CA

Tch = Cdis/I + 3 ~5

(2)Discharge current: Less than 0.25CA

Tch = Cdis/I + 6 ~10

Tch: time required for charge (hours)

Cdis: ampere-hour discharged before

charge started(Ah)

I : initial charging current(A).

Complete charge time for float service will be slightly more than 24 hours.

Note: The minimum recharge capacity should be 1.02~1.05 times of discharge capacity

• General Storage Conditions:

The battery should be stored under the following conditions.

1. Low humidity
2. 5 to 122oF(-15 to 50oC)
3. Clean, and avoid direct sunlight.

• Capacity after Long Term Storage

After long term storage, all batteries deliver less than rated capacity on first cycle. In cyclic application, full capacity may be obtained through several charge/discharge cycles, typically 2-3 cycles.

• Refresh Charge

When batteries are placed in extended storage, it is recommended that they receive a refresh charge at recommended intervals as following;

Refresh charging method:

3 to 5 hours of constant current 0.1C Amps or 12 to 16 hours at constant voltage of 2.45V/cell

• Never charge the battery in a sealed container.
• Never disassemble the battery.
• Never short-circuit battery terminals.
• Never incinerate batteries, for they may explode.
• Do not press and/or bend the terminals, or overheat them.
• Do not mix old and new batteries together, neither use batteries of different types
• Do not dispose of with household waste.
• Be sure to use the specified charger for battery, and follow the charging instructions correctly.
• Be sure to charge the batteries between the temperatures0oC/32oF to 45oC/113oF.
• Be sure to position batteries securely, protecting them from abnormal shocks and /or vibration.
• Be sure to keep sufficient space between batteries for ventilation (where possible>10mm).
• Be sure to install batteries in a cool and well ventilated place.
• The surrounding temperature must remain between-20oC/4oF to 40oC/104oF during storage.
• Recharge the batteries at least every 6 months during storage.
• Be sure to consult WBDengineers any time you are to use WBD VRLA batteries for your products, or preparing your technical specifications of WBD VRLA batteries