Precautions on Battery Charging

This information was obtained from the Panasonic Sealed Lead Acid Batteries Technical Handbook, 1998-1999 It applies to most sealed lead acid batteries.

1. (a) in constant voltage charging (cycle use): Initial current should be 0.4 CA or smaller (C: rated capacity)
(b) in V-taper charge control system: Initial current should be 0.8 CA or smaller (C: rated capacity)
(c) in constant voltage charging (trickle use): Initial current should be 0.15 CA or smaller (C: rated capacity)

2. Relation between standard voltage value in constant voltage charging and temperature is given in the Table.

a) Temperature compensation of charge voltage
Charge voltage should be compensated to the ambient temperature near the battery, as shown by the figure below. Main reasons for the temperature compensation of charge voltage are to prevent the thermal runaway of the battery when it is used in high temperature conditions and to secure sufficient charging of the battery when it is used in low temperature conditions. Prolongation of service life of the battery by the above - described temperature compensation is expected as follows

At 86°F (30°C): prolonged by approx. 5 %

At 95°F (35°C): prolonged by approx. 10 %

At 104°F (40°C): prolonged by approx. 15 %

b) Charging time
Time required to complete charging depends on factors such as depth of discharge of the battery, characteristics of the charger and ambient temperature. For cycle charge, charging time can be estimated as follows:

(1) when charge current is 0.25 CA or greater: Tch = Cdis / I + (3 to 5)
(2) when charge current is below 0.25 CA: Tch = Cdis / I + (6 to 10)
Where:
Tch : Charging time required (hours)
Cdis : Amount of discharge before this charging (Ah)
I : Initial charge current (A)

Time required for trickle charge ranges from 24 to 48 hours.

c) Charging temperature
(1) Charge the battery at an ambient temperature in the range from 32°F(0°C) to 104°F (40°C).
(2) Optimum temperature range for charging is 41°F to 95°F (5°C to 35°C).
(3) Charging at 32°F (0°C) or below and 104°F(40°C). or higher is not recommended: at low temperatures, the battery may not be charged adequately; at high temperatures, the battery may become deformed.
(4) For temperature compensation values, see a).

d) Reverse charging
Never charge the battery in reverse, as it may cause leakage, heating or bursting of the battery.

e) Overcharging
Overcharge is an additional charge after the battery is fully charged. Continued overcharging shortens the battery life. Select a charge method which is specified or approved for each application.

f) Charging before use
Recharge the battery before use to compensate for capacity loss due to self-discharge during storage.

Charging Index

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