In today’s world, storage batteries are playing an important role, generally, as a backup or standby power to many applications like in telecom sectors, electric power systems, computer application to protect from data loss, etc. Battery Chargers are automatic D.C. power sources meant to feed the connected load and simultaneously charge the connected battery. It maintains the continuously healthy and ready to feed condition of the battery in an emergency situation of A.C. supply failure. This arrangement ensures an uninterrupted D.C. supply to the connected load at all times – by the battery charger in case of A.C. power supply availability or by the battery in case of failure of A.C. Power Supply. Batteries make this power source available for the successful operation of switching and control devices in power protection system.
But the question arises is “do batteries will always operate when needed to operate?”
If yes then the battery should always be in good condition so that it can operate during a power failure and it should be maintained through regular inspection, maintenance and testing of batteries.
If regular inspection or testing of battery is not done then many problems would arise which can reduce the working life of a battery, some of these problems are listed below
- Absence of proper ventilation
- Deterioration of connections and leakages
- Variation in voltage from cell to cell
- Battery charger settings
- Cell post damage
Testing should be done in accordance to two points; firstly it ensures that the batteries meet the qualifications of both manufacturer and consumer and secondly it provides a reference point for comparison for future testing.
Here testing can be divided into two subgroups
- Performance testing
- Qualification testing
Performance testing provides the data about the present condition of the battery, working voltage, capacity, etc. and also provides information about any problem in battery which is required to meet the working of the system.
Qualification testing is done to ensure that whether the capacity of the battery is sufficient or not to meet the system requirements.
Maintenance requirements involve both periodic maintenance and periodic testing. Maintenance includes visual inspection, checking and restoring electrolyte (water) levels, measuring individual cell specific gravity temperature and voltage readings, cleaning and retorquing terminal connections, etc.
Above mentioned tests require some instruments, and they are
- Digital hydrometer
- DC load bank
- Internal resistance testing kit
- Hydrogen gas detection kit
Some conventional methods of battery tests are
- Visual Inspection – It includes finding the location of the crack, leakage, corrosion if any.
- Float Voltage – Check that battery should not be grounded at either end. Instead, it should float with both ends above the ground. We can check it easily with the help of voltmeter.
- Specific Gravity Measurement – This can be measured with the help of hydrometer. The specific gravity of healthy battery should be in the range of 1.19 – 1.27. Because Specific gravity is a great way to know the battery’s state of charge.
- Charging or Discharging Test – Charging or discharging battery test can be done by knowing the value of current at that instant of time. If the value of current is increasing, then it will be the state of charging and vice-versa.
- Temperature Testing – Temperature of battery should be maintained at a specified level, as the life of battery reduces with increase in temperature. The thermal imaging method is used for finding hot spots inside the battery, which indicates high thermal stress in the battery cells.
- Impedance Testing – Impedance of the battery will increase as the battery deteriorates, while conductance decreases.
- State of Charge (SOC) – It indicates how much of energy is left in a battery.
- State of Health (SOH) – It measures battery ability to deliver current when required to supply.