Individual battery and string parameters

PowerShield systems provide permanent and continuous monitoring for stand-by battery installations. Individual battery and string parameters are measured against user-defined limits specific to battery state (float, idle, charge and discharge) supporting both float and intermittent charging regimes.


Individual Battery Voltage

Correct float voltage is critical for battery life. Incorrect charge voltages may result in loss of capacity, accelerated grid corrosion, excessive gassing and premature end of life. Voltage also identifies catastrophic failures, such as short circuit cells, and gives true visibility of performance under discharge.


Individual Battery Impedance (Ohmic Value)

The impedance of a battery will increase with age. High impedance results in a battery that cannot supply the required current – its key task. By trending impedance you can accurately determine end-of-life. High impedance readings also highlight poor connections and open circuit batteries before failure.

Batteries can fail in a very short period of time (less than a week) so measuring impedance daily allows you to detect faulty batteries – without the need to discharge them.


Individual Battery Temperature

Measuring the temperature of each battery allows the early detection of thermal runaway. It pinpoints localized environmental problems through poor HVAC, and can also highlight poor connections under discharge and excessive charger ripple. A common failure mode for Ni-Cds is separator failure which can be detected with temperature.

Ambient Temperature

A battery’s life-span is normally specified at 20 or 25 degrees celsius. Temperatures outside of the specified range can significantly affect the battery’s corrosion rate, and therefore the life of the battery. An 8-10 degree temperature increase can decrease battery life by 50%.


String Current

String current monitoring measures the energy delivered or accepted by each battery string. A UPS will only measure total current and cannot detect imbalances between strings. An imbalance highlights potential problems within a battery string.
String current measurement also allows detection of incorrect battery charging and any significant earth leakage faults.

String Ripple Current

Detect excessive ripple current or unexpected changes over time.


String Voltage

Tracking the string voltage confirms the charger is operating and the batteries are being charged at the correct voltage.