Eagle Eye Power Solutions

Vigilant FAQs

This page outlines various FAQ questions, organized into categories.

General FAQs

The Vigilant monitors the following parameters and records them at the specified interval:

  • Float voltage
  • Float current
  • Charge & discharge current
  • Ambient temperature
  • Cell/unit voltage
  • Cell/unit resistance
  • Interconnection resistance
  • Terminal resistance
  • Negative post temperature (per every cell/unit)
  • Electrolyte level
  • Ground fault

See the Battery Monitoring for NERC Compliance page. This page outlines how the Vigilant meets each attribute of NERC PRC-005-6.

Yes, see the Battery Monitoring for NERC Compliance page. This page outlines how the Vigilant meets each attribute of NERC TPL-001-5.

The Vigilant is designed to work with most stationary battery types, including VLA/flooded, VRLA/sealed, and Ni-Cad batteries. The exception is Lithium-Ion, which the Vigilant is not compatible with.

While the Vigilant can provide an overall idea of battery health, it does not explicitly state whether a battery is bad or not. The system will provide many parameters necessary to allow the end user to make a judgement call on whether or not a battery should be replaced. A future update will provide functionality to estimate the remaining life of a battery using machine learning algorithms.

Installation & Service FAQs

Installation & commissioning of the Vigilant system is required to be performed through Eagle Eye Services or a certified third-party contractor.

At this time we discourage installation of the Vigilant system by the end-user. The system requires specific tools and training in order to be successful. Installation options can be discussed with a salesperson or your service contact.

Installation time can vary depending on a number of factors such as battery size, battery type, site conditions, etc. The typical 60-cell battery system can be installed in 10-16 hours by a certified installer.

It depends on the battery type, or more specifically how exposed the battery posts are on the system. The Vigilant has 2 main connection types to the battery which determine if the installation can occur with the battery in service:

  • Clamp Connections: If the battery has an exposed square post, the Vigilant can be installed by connecting steel clamps to each battery post. The clamp is fixed to the post with 2 screws that do not interfere with the battery. These posts are typically seen on VLA/flooded batteries, but also some VRLA/sealed designs.
  • Tab washer Connections: If the post is recessed, covered, or otherwise not accessible then a tab washer is typically used for connection. Installation of tab washers requires the system to be taken offline for 30-40 min. This is typically seen on most VRLA/sealed, front facing, and OPzS battery designs.

The system as shipped includes all core components of the system: the monitor, sensors, connection hardware, and wiring harnesses. Additional wiring specific to the site will be provided by the installer at time of installation. This includes power cabling, longer sense leads for jumpers, and longer comms cabling between sensors. The system does not include Ethernet between the monitor and the network.

Every cell/unit on the battery system is assigned a single Vigilant sensor. That sensor is wired directly to the battery connections with as short of wire as possible. All sensors are connected in a loop via RJ12 comms cable back to the monitor. This allows the sensors to be powered from the monitor while greatly reducing the amount of sensing cables required. Eagle Eye has past provided systems with longer cable runs as well as wireless technologies and found that both are subject to noise from the environment, decreasing the reliability of the system overall.

Software & Communication FAQs

At a minimum, an up-to-date web-browser is required to login and view the web-interface. This can be done on most devices such as smart phones, tablets, laptops, and desktop computers.

No additional software is required to use the system; however a Fleet Management Software is available for monitoring a large number of systems on a single network.

All measured data is stored on an SSD in each individual Vigilant Monitor. The SSD is sized to accommodate 20 years of measured battery data. A permanent connection to the monitor is not required for the system to measure and record data.

Update files are available on the Eagle Eye website (see Support) and uploaded on the monitor by the end-user. They can be installed over network of via direct connection to the unit. Eagle Eye also offers a service to perform updates if requested.

A newsletter will be released as new updates are available.

The Vigilant has a built-in web server with a dedicated IP address (default is The web server can be accessed on a web browser from any PC on the same network via the monitor IP address. The IP address can be set to DHCP or a static. An internet connection is not required, nor are there any cloud based features on the system.

The Vigilant system has an Ethernet port for connection to a network or direct connection to a computer. Both access the web-interface and Modbus communication can occur simultaneously over this port.

For hard-wired alarming, the system has (2) dry contact relays.

Port 80 is the primary port for communication and control of the Vigilant monitor. If using Modbus port 502 and 0502 are needed.

Currently Modbus TCP is the only external protocol supported. DNP3 protocol is in development for release in 2023.

The following protocols are not supported: SSH, HTTPS, Telnet, and SNMP.

System logs are accessible by Eagle Eye service only and are used for troubleshooting device failure. Customer accessible system logs may be provided in a future update.

All collected data residing on the Vigilant monitor/manager web-server may be accessed via internal networks (if the battery is on-site or available to those networks, – such as remote sites coupled to the company net by wireless or land-line). The system appears as a web site, and can be accessed and navigated as such. If the system is accessed via the internet, again it will be accessible by use of a URL exactly the same as any website.

All data will remain in the Vigilant memory for the life of the SSD memory (see the Vigilant Expert data sheet). Download of the data to a company database can be achieved at any time by CSV files, Modbus or DNP3 (2023 release).

When they were introduced over 30 years ago, Battery Monitoring Systems were stand alone systems and seldom integrated into an organizations control and reporting network. With the increase in remote monitoring and the increasing risk of cyber attacks that is no longer practical.

For example, the NERC CIP -003 Standard requires that all electronic access to communicable products that are located within an Electronic Security Perimeter such as a substation. Must have access to these devices controlled by the Responsible Entity which effectively makes a battery monitor an intelligent sensor. Because the Vigilant Monitoring System does the basic alarm analysis within the controller it is ideal for this application as it does not require a secondary device to analyze and distribute the collected data, as the previous generations of monitor do.

The Vigilant has several means of alarming based on the measured parameters:

  • Monitor alarm relay: There is a single dry contact relay available for when a critical alarm occurs.
  • Modbus point: There is a Modbus point available for when either a warning or critical battery alarm occurs.
  • LEDs: There are LEDs on the front of the monitor that correspond to various alarms on the system.
  • Web-interface: All alarms are viewable on the Vigilant web-interface.
  • Fleet Management Software (optional): Critical and warning alarms are viewable for all installed systems.

Additional alarming paths are in development, including DNP3.

The Vigilant system performs many self-checks on the system sensors and the monitor itself as part of its program. Alarming is available for the following failure modes:

  • CPU failure/lockup
  • Loss of power
  • Loss of communication to sensor bus
  • Failed or disconnected sensor

The Vigilant monitor includes 2 dry contacts standard:

  • Battery alarm: Occurs when any measured parameter reaches critical alarm level.
  • Watchdog alarm: Occurs when any of the 4 watchdog parameters occur (see above FAQ)

The maximum power rating of the contacts is 300 watts, not to be exceeded. If the breaking voltage is 300V then the breaking capacity could be as high as 1A.

Hardware, Engineering, & Measurement FAQs

The Vigilant system includes the following main 4-5 components:

  • Vigilant Monitor – Stores data, runs web-server, handles communications. (1) monitor per battery system.
  • Vigilant Sensors – Measures cell/unit parameters. (1) per cell/unit, plus (1) per string.
  • Connection Hardware – Physical connection to battery post. (2) clamps or (3) tab washers per cell/unit.
  • Wiring Harnesses – Connects Vigilant sensor to battery connection hardware. (2) harnesses per cell/unit.
  • Electrolyte Level Sensors (optional) – Measures electrolyte level, (1) per cell.

This depends on the model of the Vigilant or the chosen method to power the monitor. The system can be powered off the battery or from an external power source. Below are the options to power the system:

From the battery:

  • Low voltage: 36 – 72 VDC
  • Medium voltage: 95 – 300 VDC
  • High voltage: 280 – 580 VDC


  • 24 VDC (often used for AC power with a converter)

No, all Vigilant components are powered from the monitor, which receives power from the battery charger or an external power source.

The Vigilant monitors the following parameters at the specified interval:

  • Battery float voltage (15 min.)
  • Charger float voltage (15 min.)
  • Float current (15 min.)
  • Charge & discharge current (1 sec. during discharge)
  • Ambient temperature (15 min.)
  • Cell/unit voltage (15 min.)
  • Cell/unit resistance (Once daily)
  • Interconnection resistance (Once daily)
  • Terminal resistance (Once daily)
  • Negative post temperature (per every cell/unit) (15 min.)
  • Electrolyte level (15 min.)
  • Ground fault (15 min.)

Yes, the Vigilant monitors the float current in the battery by accurately measuring the potential difference across the cell interconnections; this enables reliable detection if the battery has a continuity fault. In addition, we rely on the ohmic readings from each interconnection.

The ohmic value of a cell or unit reading can be reported as Resistance, Impedance or Conductance and which value reported is dependent on the perturbation method used. If a DC source is used, the value reported will be a Resistance. If an AC source is used, the value will be reported as Impedance. Both these methods are reporting the change in ohmic value as an increase in the opposition to current flow, whereas Conductance, which is the reciprocal of Resistance, will report the value in siemens or mhos and the value will drop as the battery ages.

In the thirty plus years that ohmic values have been part of a battery maintenance program, while the individual test equipment manufacturers have promoted the value of their specific method and while the values reported will be different, their ability to identify the level of change is virtually the same.

The Vigilant uses a DC perturbation pulse, so it reports the value as a resistance.

The Vigilant was designed to incorporate the ELM-Series electrolyte level sensors. Each ELM sensor plugs directly into the Vigilant sensor for that cell. This allows the software to display which cells specifically have low electrolyte level alarm. These alarms can be cleared from the software or in the field after a cell is refilled.

Typically, battery ground voltage (without fault) should sit midway between battery positive and negative. The Vigilant checks the ground potential relative to the battery mid-point and will detect an imbalance if the ground potential is not mid-battery voltage. The closer the ground fault to battery positive (or negative) the signal will have a higher ground leakage current. When measuring for a ground fault the Vigilant is looking for a nominal difference of 9% (not adjustable on present system). This to say, on a 120V system with the battery mid-point at 60V, if the ground voltage is below 54.6V or above 65.4V then a ground fault warning will be raised.

Be aware that some systems have one battery terminal intentionally grounded (usually positive on telecommunication systems). If this is the case then the small green wire loop in the monitor should be removed, or, do not ground the monitor chassis. This will prevent the monitor recording a ground fault.

No, this has been tested with most battery chargers on the market and there has been no conflict.

Each sensor draws a robust test current for a very short time from each cell, this results in a small momentary change in the terminal voltage. The waveshape and parameters of the change in the terminal voltage are analyzed, and from this the Vigilant can determine the cell and strap resistance.

The sensors analyze the cell energy and automatically optimize the test current to maintain a safe level of test. The actual energy drawn from the cell during the test is insignificant to the battery and is not detrimental to the cell in any way.

Standby batteries are subject to a float current all their service, lives in order to maintain them for instant use. The resulting float voltage is actually an overvoltage of approximately 150 millivolts per cell on top of the cell’s fully-charged natural open-circuit voltage.

Cell internal resistance/impedance is calculated by drawing a current from the cell in a pulse pattern and measuring the change in the terminal voltage. If too low a test current is used, several factors which can adversely affect the measurement come into play

  • The change in terminal voltage will be too small to come from the cell itself, but will come from the overvoltage, mainly influenced by the charger. If the float current changes the measurement will be different.
  • Battery system noise and ripple can obscure a small test current and lead to adulterated readings
  • A low test current means a small response signal; the smaller the signal the less accurate the measurement can be.

Yes, a temperature sensor is built into every negative post connection from the Vigilant. It is recognized in the battery industry that the negative post of the cell is the most sensitive to internal temperature variation, and if ‘acid creep’ is experienced it is inevitably at the negative terminal post first. The negative post is often at a slightly higher temperature than the positive post and in any case terminal posts are a much better indicator of internal temperature than the plastic cell casing, which is a thermal insulator and influenced by the ambient temperature. The Vigilant sensor is designed to have an excellent thermal connection to the negative post and is also insulated against the effects of changes in the ambient.

No, the Vigilant does not influence or have any effect on the cell/unit voltage. The system is designed strictly for data acquisition and is not intended to change the battery in any way.

While not directly measuring sulphation inside the cell, the Vigilant measures parameters which can indicate sulphation is present.

In a lead acid battery, when it is discharged, both the positive and negative plates will be converted to Lead Sulphate and return to Lead Dioxide and Sponge Lead when they are recharged. It is important that the battery is recharged as soon as possible, as the lead sulphate will crystallize over time, at which point no amount of recharging will change it back to its original fully charged state.

If the battery is not being charged at a high enough voltage to overcome self-discharge, lead sulfate will form on the plates, initially on the edges but eventually on the surface of the plates, and when it crystalizes, it will block the underlying active material and reduce capacity. Although in the initial stages it will not change the Ohmic measurement, once it affects the surface of the plates it will. Monitoring the individual cell/unit voltages to ensure that they are within the manufacturer’s limits should reduce the potential for Sulphation to occur. A rise in Ohmic value can be indicative of sulphation and prompt inspection of the cell/unit.

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