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CHARACTERISTICS

  • Charging

Charge characteristics (constant voltage-constant current charging) of SLA batteries are exemplified below.

Example of constant-voltage charge characteristics by current

(V/cell)

2.5

Voltage

2.0

0.4

~~

(Test condition) Discharge : 0.05 CA constant- current discharge Cut-off voltage; 1.75 V/cell Charge : 2.45 V/cell

~ ~

0.3

2.30 V/cell Temperature : 25˚C

Current

0.2

  • b)

    Discharge temperature

    • (1)

      Control the ambient temperature during discharge within the range from -15C to 50C for the reason described below.

    • (2)

      Batteries operate on electrochemical reaction which converts chemical energy to electric energy. The electrochemical reaction is reduced as the temperature lowers, thus, available discharge capacity is greatly reduced at temperatures as low as

      • -

        15C. For the high temperature side, on the other hand, the discharge temperature should not exceed 50C in order to prevent deformation of resin materials which house the battery or deterioration of service life.

0.1

(CA)

0

0

3

6 9 12 Charge time (hours)

15

18

c) Effect of temperature on discharge characteristics Available discharge capacity of the battery varies with ambient temperature and discharge current as shown in the figure below.

In order to fully utilize the characteristics of SLA batteries, constant-voltage charging is recommended. For details of charging see page 20.

Discharge capacity by temperature and by discharge current

  • Discharging

    • a)

      Discharge current and discharge cut-off voltage

Recommended cut-off voltages for 6V and 12V batteries consistent with discharge rates are given in the figure below. With smaller discharge currents, the active materials in the battery work effectively, therefore discharge cut-off voltages are set to the higher side for

controlling overdischarge.

For larger discharge currents,

on the contrary, cut-off voltages are set to the lower side. (Note) Discharge cut-off voltages given are recommended values.

Capacity (%)

120

100

80

60

40

20

    • 0.05

      CA

    • 0.1

      CA

0.25CA

1CA

Discharge current vs. Cut-off voltage

5.4

Discharge cut-off voltage (6V battery)

5.2

5.0

4.8

4.6

4.4

4.2

4.0

10.8

10.4

10.0

9.6

9.2

8.8

8.4

8.0

Discharge cut-off voltage (12V battery)

0

  • -

    20

  • -

    10

  • 0

    10 20

Temperature <˚C>

30

40

50

0.05

0.1

0.2 0.3 0.5 Discharge current (CA)

1

2

3

Sealed Lead-Acid Handbook, Page 16

January 2000

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