Battery OCV should be minimum 12.8V. If less than 12.8V, then the battery should be given a float charge till it reaches the desired voltage of 12.95 to 13V. In case the battery cannot take charge, the battery has to be replaced.
If connecting in a string, then the OCV of all the batteries in the string should be in the range of 300 millivolts of each other. For example if there are 16 batteries being connected, then the OCV ideally should be between 12.8 to 13.1V. Any higher or lower readings should be noted and the batteries given an ‘equalisation charge’. This is done by float charging the battery for a minimum period of 12 hours (13.5 – 13.8V) and then doing a C10 discharge for about 6 to 8 hours. Regular voltage readings of all batteries should be noted every 30 minutes. The cycle of charge and discharge is done till all batteries reach the desired voltage range within 300 mv. In case there’s a battery not within the range even after equalization, replace the battery.
Physically examine the battery for any sign of electrolyte leakage or visible damages to the battery container.
Check the condition of the positive and negative terminal connectors – they should not be corroded.
Site condition at time of installation:
The site should be well ventilated and airy to ensure proper dissipation of hydrogen gas that is emitted by batteries. Hydrogen is highly inflammable and therefore dangerous when accumulated in closed spaces.
Proper earth fault and insulation of the battery racks / stand to prevent current leakage to the ground.
UPS condition at time of installation:
Ensure charging current is proper.
Check float and boost voltages of the UPS. Should be 13.5 – 13.8V for float charge and 14.5 in boost charge mode with automatic return to float mode.
Other precautions:
Battery type, capacity, make and age should be similar in the string.
The correct length and cross section of interconnecting cable to be used.
Torque used will be same for type of bolt used. Torque recommendations are typically given in the battery specification sheets. It’s recommended that the technician doing installation use a torque wrench for tightening the bolts.
More than 3 strings of batteries should not be paralleled. Here, it’s recommended that each string has a separate charger to ensure proper charging.