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Ways to Properly Charge Stationary Lead-Acid Batteries

After hundreds of site visits, multiple battery systems tests, and the examination of numerous maintenance records, I would say that almost 50 percent of all stationary lead-acid batteries are not being properly charged.

Constant-Current Charging: Not generally used for stationary batteries except during the manufacturing process.

Constant-Potential / Constant Voltage Charging: Used in communications, UPS, IT, and utility applications – where the charging circuit is current limited and the voltage is maintained until a predetermined value is reached, and then the voltage is maintained constant. With constant potential charging, the charge current will decrease to a stable value as the battery becomes fully charged.

Float Charge: Used with all stationary lead-acid batteries, this is a low-rate constant-potential charge used to maintain the battery in a fully charged condition.

Equalize Charging: Mainly used with Vented Lead-Acid (VLA) Batteries. It’s similar to a boost charge where a voltage higher than the float voltage is applied to a battery to the correct voltage or specific gravity (SG) inequalities among battery cells.

Voltage Drop: Allow for the ohmic resistance of the cabling from the charger to the battery, which could cause a voltage drop. The float voltage setting should be measured and set at the battery terminals.

Electrolyte Level Monitoring: Correct overcharging within 72 hours of elevating equalize charging current to avoid excessive gassing before re-applying an equalize charge. I don’t quite understand the above. Replace with – Before applying an equalize charge ensure that the electrolyte level is not too high and monitor the electrolyte level during an equalize charge as the charge may cause the level to rise.

VRLA Gassing During Equalize: Equalize charging is not normally recommended for VRLA Batteries unless requested by the manufacturer for various reasons. A charge voltage higher than float may cause excessive gassing and lead to dry-out or thermal runaway.

Temperature: Change to the following: Maintain optimum performance by operating the battery at the North American recommended nominal 77° (25°F) temperature, and above or below this temperature norm, compensate the charge voltage appropriately to prevent the battery being under or over charged.

Following the techniques in this article will help you avoid typical battery charging pitfalls, preserving the life and integrity of your lead acid battery, and saving the time and cost associated with battery maintenance and replacement.

For more in depth information on battery charging, see the white paper “The Proper Charging of Stationary Lead-Acid Batteries.” Or, download the infographic.

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