Eagle Eye Power Solutions

Battery Monitoring for NERC Compliance

The Vigilant-NERC system is Eagle Eye’s complete battery monitoring solution for NERC PRC-005-6 Compliance. This standard requires utilities to document and implement programs for the maintenance of all protection systems affecting the reliability of the bulk electric system (BES).

Under NERC PRC-005-6, battery maintenance falls under Table 1-4(f) “Exclusions for Protection System Station DC Supply Monitoring Devices and Systems” with no maximum maintenance interval. This table outlines the monitoring and alarming requirements needed to alleviate periodic on-site maintenance activities.

Monitoring for NERC Compliance

The attributes in Table 1-4(f) call out monitoring and alarming of the key battery parameters listed below. The Vigilant complies in monitoring all of these parameters:

  • String Voltage: Provides high and low monitoring and alarming of string voltage at the battery positive & negative terminals.
  • Electrolyte Level: Provides alarming and identification of low electrolyte level for every cell with infrared ELM sensors.
  • Ground Fault: Provides monitoring and alarming for unintentional DC ground fault by measuring earth potential relative to battery voltage.
  • Float Voltage: Provides monitoring and alarming of float voltage at the battery positive & negative terminals to ensure correct float voltage is being applied.
  • String Continuity: Monitors the precise float current in the battery by accurately measuring the potential difference across the cell interconnections, enabling reliable detection if the battery has a continuity fault.
  • Intercell and Terminal Connection Resistance: Provides monitoring and alarming of battery terminal resistance and each intercell connection resistance as independent values.
  • Internal Ohmic Value & Float Current: Provides monitoring and alarming of each cell’s internal resistance against an established baseline.

Reporting for NERC

The key element to meeting NERC compliance for battery monitoring is have access to detailed reports that prove compliance to the standard. The Vigilant provides one-click NERC reporting to make this step as easy as possible and remove the guesswork of what needs to be included. Using the built-in web-server, the Vigilant can generate a detailed PDF report.

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Working Voltage0.05 – 18.5VDC
Voltage Resolution± 1mV
Post Temperature Resolution± 1ºC
Cell Resistance Resolution± 7μΩ
Strap Resistance ResolutionAt 100μΩ strap r: ± 2μΩ
Float Current ResolutionAt 100μΩ strap r: ± 1mA
Charge/Discharge CurrentMax 800μΩ strap r: ± 0.1%
Max 400μΩ strap r: ± 0.1%
Range: 2,000A
Electrical Supply (from DC supply)36 – 72VDC, 90 – 300VDC, 280 – 580VDC
Other Power Options24V mains supply
System Internal Powervia comms system
Operating Power (from charger)@ 60 cells: 25W
Operating Temp Range-4 – 70 ºC (25 – 158ºF)
Isolation I/P to O/P1000VDC
Test current @ 2.5V20A
Onboard StorageSSD
Memory Capacity20 years of battery data average, expandable for larger systems
Local Data DownloadVia USB port
External ProtocolsModbus TCP/IP, DNP3
Network InterfaceRJ45 Ethernet
Dimensions (L x W x H)Monitor: 50 x 50 x 25 mm (2 x 2 x 1 in.)
Sensor: 242 x 200 x 65 mm (9.5 x 8 x 2.6 in)


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