►Extent battery life with maintenance
Get the maximum out of VRLA Battery: Proper installation & maintenance will make batteries last longer and perform to its requirements.
Battery room inspection is easy: Battery local environment check is a pre-requisite togood installation of VRLA batteries.
Cabling inspection is a must for safe operation: Batteries are sized for a specific load for a specific run-time and for a specific end voltage.
►Initial check and start up:
Battery system ground fault detection:
• If a ground fault detection system exists, it should be used to determine the safety level of the system.
• If not a digital voltmeter can be used to measure the voltage between each polarity and the ground.
• Depending on the grounding of the system, for a Sound battery, readings should be:
- 0 V 0V for grounded polarity
- Float charge DC voltage for the other polarity,
- 0,5 x float charge voltage for middle point grounding.
Freshening charge after storage:
When batteries have been in storage for an extended period, a freshening charge is recommended prior to start up.
Initial “float” charging:
Following the freshening charge, the battery system should be put on a float voltage of 2.25 – 2.3 Vdc per cell
(i.e.: 13.5 to 13.9 Vdc for 12V battery block).
Battery system float charging voltage:
For VRLA battery, e.g.: C&D – DNT range, having a specific gravity of 1.280 to 1300, float charge voltage is:
2.25 to 2,3 Volt x number of cells.
DC voltage adjustment vs temperature:
For temperature higher than 25°C, float charging voltage should be compensated, i.e.: - 0.005 Vdc per °C above 25°C
Environment, ambient and battery Temperature:
While VRLA battery will function at extremes of Temperature, it is rated at 25°C.
Ideal operating temperature is 21°C to 17°C:
• cooler temp. reduces standby operating time,
• warmer temp. reduces battery life time.
( e.g.: 10°C above 25°C 50% life reduction)
Battery visual inspection:
Individual battery blocks should be kept cleanand properly spaced.
Container & cover damage:
• Presence of a crack on container of cover could allow leaking of conductive electrolyte. (risk of short-circuit
or ground fault) battery block replacement is needed,
• Presence of a hole in the cover may allow drying up of Electrolyte and heating of the battery cell,
• Bent or otherwise damaged terminals can produce high resistance and battery having damaged terminals
need to be replaced.
• If the protective grease at a termination has melted and flowed onto the cover it is an indication of overheating connection should be disassembled and inspected.
• Excessive float charging voltage will create excessive current, plate corrosion & electrolyte drying.
• Severe overcharging can result in pre-mature battery aging & loss of capacity..
• To prevent risk of battery aging, DC ripple should also be monitored to less than 0.5% of DC voltage.
(e.g. < 2.07 V rms for a 414 Vdc float voltage)
Battery block replacement:
Battery replacement cannot be avoided in the following cases:
• battery capacity below 80% of the manufacturer’s rating
• visual inspection showing one of the following
- Cracked jar,
- Cracked cover,
- Deformed jar / cover,
- Wetness around cell.
Conditions for compatibility:
When replacing a battery block in a string it is recommended to use a battery block of same size and identical electrical characteristics.
This is to ensure balancing of float voltage across the string.
The new block should be fullt charged before implementation.
After replacement a equalization charge could be performed If necessary.
Battery replacement need to be done by qualified personnel forsafety reason, and to ensure optimal recovery of battery
Typical battery maintenance program:
- Room condition and availability of safety equipment,
- Air temperature in the room,
- Visual inspection of battery (cleanliness, terminal & container damage or overheating),
- DC float charging Voltage
- DC voltage of each polarity to ground
- DC & AC float charging current,
- Temperature of battery pilot unit,
- Individual unit DC float charging voltage,
- System equalization voltage
Semi-annual, to be added:
•10 sec. high rate (e.g.:100A) load test,
• Resistance, conductance, impedance of individual units
Annual, to be added:
• Re-torque all inter-unit connections
Bi-annual, to be added
• capacity testing (vs 85 % of rated Capacity)