Application Notes - Battery Storage System Issues
Battery systems are becoming more common and increasingly important for modern living. Many homes, offices and businesses are being fitted with battery storage systems to either store solar energy or off-peak grid supplied energy for later use. Some systems use the battery of an electric vehicle to store and reuse this energy. Businesses and homes are having charging stations or points installed to allow charging and/or discharge of this DC energy from their vehicles.
With a domestic solar battery storage system, the battery is charged via excess solar energy and then (if needed) topped-up with off-peak energy for the forthcoming day. These systems are very sophisticated and automatic, they are however degraded by poor and/or incorrect installation. Users sometimes need to know that the system is running as planned, this involves recording the battery current and its direction, in other words, whether and when it’s charging or discharging. Since the systems are designed to be automatic, they can develop faults or be running non-optimally and the user completely unaware.
We have experienced systems that never charged the battery with the excess solar energy and only ever charged via off-peak grid supplied energy due to incorrect installation.
Other systems never used the battery power for local power needs, so excess solar power was always exported and then bought back, the battery was only ever topped up and never drained, due to incorrect installation.
Other systems had faults with the battery, so the battery storage became unavailable, however the owner was not aware.
Logging the DC voltage and current with the Electrocorder DC-3VA was crucial to determining these diagnoses.
The DC-3VA has a directional DC current probe, which measures the magnitude and direction of current, this allows the user to determine the direction of flow, charging or discharging. The recorder also measures two channels of DC voltage to 300Vdc. Correlating the voltage to the current can give an indication of the battery’s internal resistance and its charge level, as well as its overall health. If for example the battery voltage starts to drop under normal load, this would indicate that the battery capacity is lower than it should be, perhaps it was underspecified or it has developed a fault, or indeed the normal loading level has increased and the battery size need to be increased.