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Charging Methods

The capacity or life of the VRLA batteries is influenced by environmental temperature, charging voltage and other parameters. So charging methods is important to the VRLA batteries.
1¡¢Charging methods and battery application (Note: all at 25oC/77oF)

Application¡¡Charging
Method
Standby/Backup Use Main Power use Refresh Charge
During Storage
Float¡¡Charge¡¡Operation Trickle
Charge Operation
Cyclic Charge Operation
ºãѹ³äµç Regulation range of controlled voltage: Regulation range of controlled voltage
2V£º2.25 ~ 2.30V   2V£º2.43 ~ 2.50V  
4V£º4.50 ~ 4.60V   4V£º4.87 ~ 5.00V  
6V£º6.75 ~ 6.90V   6V£º7.30 ~ 7.50V  
8V£º9.00 ~ 9.20V   8V£º9.73 ~ 10.00V  
12V£º13.50 ~13.80V   12V£º14.60 ~ 15.00V  
Initial current: No limit   Initial current: 0.3C or less
he current capacity of charger must be big enough to maintain the specified charging voltage during float. Some safety devices, such as thermostat, fuse and others are recommended to be installed   Several of the same model batteries, under the same storage, can be charged in series. Otherwise they should be recharged in separate groups
The charge voltage must be regulated precisely. Otherwise, batteries may be overcharged or undercharged.
The charge voltage should be adjusted when batteries are used in a wide range of ambient temperature.
Constant current charge Constant current charge Charging current: approx. 0.1C Charging time control is strictly recommended because overcharge is more likely to occur.
Two-steps combination charging   Regulation range of controlled voltage:    
the fist step:      
2V£º2.43 ~ 2.50V      
4V£º4.87 ~ 5.00V      
6V£º7.30 ~ 7.50V      
8V£º9.73 ~ 10.00V      
12V£º14.60 ~ 15.00V      
the second step:      
2V£º2.25 ~ 2.30V      
4V£º4.50 ~ 4.60V      
6V£º6.75 ~ 6.90V      
8V£º9.00 ~ 9.20V      
12V£º13.50 ~13.80V      
current: 0.3C or less      

2¡¢Charge Temperature Compensation

2.1 Electrochemical activity in a battery increases as temperature rises and conversely decreases as temperature falls. Therefore, when temperature rises, the charge voltage should be reduced to prevent overcharge, and when temperature falls, the charge voltage should be increased to avoid undercharge. Generally, use of a temperature compensated charger is recommended in order to obtain optimum service life. Charging temperature adjustment as following:

2V battery: U=U0£­(t£­25)¡Á0.003 U: actual charging voltage
4V battery: U=U0£­(t£­25)¡Á0.006 U0: charging voltage at 25¡æ(77OF)
6V battery: U=U0£­(t£­25) ¡Á0.01 t: temperature 8 V battery: U=U0£­(t£­25) ¡Á0.012 t: temperature
12V battery: U=U0£­(t£­25) ¡Á0.018

2.2 Temperature compensation of charging voltage is not required when using the batteries within 15¡æ(59 OF) to 35¡æ(95OF) range.

3¡¢Constant Voltage Charge for Cyclic Use
For rechargeable batteries, the time required to complete each charge depends on the discharged condition of the battery, characteristics of the charger. Details as the following:
a) If the discharge current is large than 0.25C: T=C/I+(3to5 hours)
b) If the discharge current is less than 0.25C: T=C/I+(6to10 hours)
T£ºTime required for charge (hours)
¡¡¡¡ C£ºDischarge capacity before charge (Ah)
¡¡¡¡ I£ºInitial charging current (A)

4¡¢Trickle Charge
Block diagram of a trickle charging system is shown in Fig.
¡¡ In this system, AC power is normally supplied the equipment and batteries are normally kept in fully charged condition and not connected to the load. If AC power fails, a relay circuit connects the batteries to the load and battery power is supplied. This charging method requires longer time for a full charge. Therefore it is necessary to use a charger that has small deviation to charging voltage, and is controlled within a narrow range of charging voltage.

5¡¢Float Charge
Block diagram of a float charging system is shown in Fig. In this system, the load and the batteries are connected in parallel with the rectifier. In this case the power source is a constant voltage charger. Float charging is used not only for back-up source, but also for AC/DC two- way applications.

 

 

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