How to Equalize Batteries?

Equalization of batteries is an important process in battery maintenance of battery banks. Fully charged batteries are equalized to bring uniformity in voltage levels of charged batteries in the battery bank. Battery equalization improves performance, efficiency, backup duration and life of the batteries.

Flooded batteries like tubular lead-acid (TLA) batteries should be equalized once every 180 days or after every 18 to 24 (charge and discharge) cycles of the battery bank. Valve-regulated Lead-acid (VRLA) batteries should not be equalized as any lost electrolyte cannot be replenished, leading to reduced life of the batteries.

Here is a brief procedure outlining how to equalize batteries along with the tools, spares, safety equipment and other materials required for equalizing the battery.

Material and Usage

  • Rubber or Latex Gloves (industrial gloves are preferred)
  • - To avoid contact with corroded particles, lead debris and the battery electrolyte (diluted acid) during equalization of the batteries

  • Safety Glasses or Goggles (industrial goggles are preferred)
  • - To avoid any dust, debris and the battery electrolyte getting into the eyes during equalization of the batteries

  • Dry Cotton Waste (a handful of cotton waste is usually required)
  • - To clean the surface of batteries and any liquid spills (especially from venting of the batteries)

  • Pair of Spanners (10-11 and 13-14 size spanners are usually required)
  • - To disconnect and reconnect the battery cables to the battery terminals

  • Distilled Water Kit (includes tools and consumables for topping-up the batteries)
  • - To replenish the battery electrolyte as required during equalization of the batteries

  • Battery Equalizer
  • - To equalize batteries at required settings or as specified by the manufacturer

  • Multimeter, Ammeter (with temperature gauge) and Hydrometer
  • - To measure battery voltage, current, temperature and specific gravity (of the electrolyte) during equalization of the batteries

  • Notepad (or plain paper)
  • - To note down, if required,:
    - – The date and time of the battery equalization
    - – The battery voltage and individual cell voltage
    - – The battery charging current and temperature
    - – The specific gravity of the electrolyte in each cell
    - – The amount (in litres) of distilled water topped up in each battery cell and battery
    - – Any other observations of importance

Step-by-Step Procedure

  1. Switch off the charger, inverter or UPS connected to the battery bank
  2. Disconnect the main negative and positive battery cable connected to the battery bank, using appropriate size spanners
  3. Clean the surface of battery with dry cotton waste
  4. Check the level of battery electrolyte in each battery cells and top-up with distilled water wherever the battery plates are exposed or about to be exposed
  5. Connect the battery bank to the battery equalizer, with battery cables,  using appropriate size spanners
  6. Set and apply equalizing charge from the battery equalizer as specified by the manufacturer or to about 5 to 10% more than the recommended battery charging voltage or about 14.40 to 16.20 volts
  7. Monitor voltage and current applied to the battery bank directly using multimeter (or voltmeter) and ammeter, if not indicated on the battery equalizer. Ensure measurements are under safe thresholds at all times to continue with the battery equalization
  8. Monitor temperature of the batteries every 30 to 60 minutes using the temperature gauge, and stop the equalizing charge if the battery temperature exceeds 46 °C. In such cases, battery equalization is resumed only after the batteries cool to room temperature
  9. Monitor specific gravity of the battery electrolyte every 30 to 60 minutes using hydrometer, and stop the equalizing charge when the specific gravity of the battery electrolyte reaches 1.265 and no longer rises with further equalizing charge
  10. Disconnect the main negative and positive battery cable connected to the battery equalizer, using appropriate size spanners
  11. Allow the batteries to cool to room temperature and then replenish the lost battery electrolyte by topping-up the batteries with distilled water
  12. Connect back the battery bank to the charger, inverter or UPS, using appropriate size spanners
  13. Switch on the charger, inverter or UPS connected to the battery
  14. Collect the tools, spares, safety equipment and other materials used for equalizing the battery

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