What is conductance?

Conductance describes the ability of a battery to conduct current.In scientific terms, it is the real part of the complex admittance. Various test data have shown that at low frequencies, the conductance of a battery is an indicator of battery state-of-health showing a linear correlation to a battery’s timed-discharge capacity test result. Trending this measurement can be used as a reliable predictor of battery end-of-life.

What is ohmic analysis?

In simplest technical terms, ohmic technology is based on Ohm’s Law, which expresses the relationship between volts, amperes and ohms in an electrical circuit.Ohm’s law can be expressed as follows:Volts (E)= Amperes (I) x Ohms (R). If any two of the three values of voltage (volts), current(amperes) or resistance (Ohms) are known, the third value can be calculated using the above expression of the law. Thus, Ohmic technology attempts to use voltage and current to determine the resistive characteristic of a battery. Higher resistance equates to a reduced ability to produce current. This characteristic is translated into a measurement of resistance or impedance(Ohms) in some Ohmic technologies; more recent technology uses a converse measurement,called conductance. Through years of laboratory and field-based research, conductance has been found to correlate with battery capacity as measured in a timed discharge test.Since voltage and specific gravity testing are not predictive, timed discharge testing is very time consuming and expensive, conductance testing is a very effective and economical way of analyzing the health of your battery systems.

How long has the Midtronics conductance method been used for testing batteries?

The original technology was developed by Motorola in the 1970s for testing automotive batteries. Today’s products are manufactured under license from Motorola, and include many new patents in North America, Europe and Asia. Midtronics has been developing and manufacturing conductance testers for more than twenty years, and customers include the world’s major battery manufacturers, major automotive manufacturers, telecommunications providers, electric power utilities, UPS manufacturers, and organizations in a variety of other industries. Midtronics has manufactured tens of thousands of battery conductance testers under the PowerSensor™, Midtron®, and Celltron®brands, as well as various private labels. Our products are manufactured and used extensively throughout the world, making Midtronics the leader in battery management technology.

Has conductance been proven and accepted by the international community?

Yes. Extensive data has been gathered by the global telecommunications industry, battery manufacturers worldwide, international rail and transportation providers, and the electric power industry.

Since the qualitative conductance test requires a standard, how can that standard be established?

The most effective method for the establishment of a reference requires the performance of a timed discharge test to locate a cell or battery that performsto100% of the rated discharge capacity. A conductance test can then be performed and a reference established.A sample of 20 or more new batteries can also be used to establish a standard. Without a set reference value,conductance testing can still be utilized to trend state of health, as batteries can be monitored through periodic conductance readings and the observation of deterioration over time.

Will the battery manufacturer have reference numbers for my batteries?

Many battery manufacturers now publish conductance reference or base line values. If not, a specific reference value can be established during installation for a new,healthy battery. An average can also be used from a sample of batteries of the same model, manufacture date, installation date and service history as detailed in the operating guidelines and instruction manuals.

What if the batteries I am testing are really old? How do I determine a reference number?

For older batteries, combine conductance testing with a full physical inspection for any visible faults. Utilize the highest measurement as an initial benchmark and the string average as a starting 30% below the highest jar,consider a discharge test to determine actual run-times.

Can conductance be used to evaluate the quality of inter-cell connections?

Yes. Since a conductance reading of a cell plus an inter-cell connection can easily be related to the conductance of the cell alone, conductance provides a very simple and reliable indication of the system's inter-cell connection integrity.

Can Midtronics conductance testers measure thecondition of sealed valve-regulated batteries as well as flooded cells?

Yes. Correlation studies have been performed on a significant number of valve regulated cells. These studies have shown that conductance test results are very predictive of battery timed discharge capacity, while voltage measurements are shown to be of little value. This data has been presented to a number of international organizations.Additionally, recent data includes gel batteries,and flooded cells.This data has been presented to the IEEE Standards Committee, which now includes conductance testing in the standard for testing sealed valve-regulated batteries.Additionally, the data has also been presented to the International Lead Zinc Research Organization, the Battery Council International, and the International Telecommunications Energy Conference.

What is a conductance reference value?

A conductance reference number is a benchmark value which is based on data collected of known good batteries. It is important to remember that a reference value provides an estimate of where the reading should be, but it is not an exact value. Trending the life of the battery using conductance, over time, is the best method.

Can a measurement be conducted without a reference value?

Yes. First, take the age of the batteries into consideration If the batteries are 1-5 years old, then take a few of the highest conductance measurements and use the average of those values. If the batteries are more than5 years old, use the highest reading. If the batteries are less than 1 year old, the string average can be used.New batteries should read within 15% of each other.These are general guidelines. Some CELLTRON analyzers include a "Reference Developer" built-in to help facilitate this process.

How can conductance readings be used with a reference value?

A significant number of tests on a variety of valve regulated lead acid (VRLA) batteries demonstrate that conductance is predictive of battery state-of-health.Since conductance is directly related, and very nearly linear with timed discharge capacity, a reading of the percentage of a known conductance reference value is a reliable predictor of a capacity test result. The conductance test gives a quantitative measurement in Mhos (or Siemens), as well as a qualitative indication(percent of reference) of a battery as related to a standard.

What is the proper method of interpreting conductance?

Trending is the preferred method. Taking a "snapshot" may not provide enough information required for are liable health indicator or warranty administration.Unlike other testing techniques that require interpretation and mathematical calculation, conductance readings can be read instantly and can be related directly to the condition of the battery being tested. Midtronics testers also output a percentage of the reference with a pass/warning/fail threshold built in.

What kinds of batteries and cells can be measured utilizing conductance?

Typically any 2-volt to 16-volt, lead-acid, 1 to 6000ampere-hour cells can be tested.

Can a Midtronics conductance measurement be made while the battery is on?

Yes. The current test technology enables successful testing of batteries while on float charge. In certain cases, an excessive amount of AC ripple current can interfere with any test method. If this is the case,consult with Midtronics as certain products were specifically designed for these noisy systems.

How large are Midtronics conductance testers?

All Midtronics conductance testers are hand-held portable instruments. They are built to very rugged standards, yet weigh less than 3 pounds (1 kilogram)each. The testers are easily transportable and each includes some form of protective carrying case.

What is the optimal point of contact when making a conductance measurement?

Making direct contact with the lead post will usually provide the most consistent and accurate test result.In order to facilitate this contact (which can be difficult depending on the battery post design),Midtronics offers a variety of battery test interfaces,including clamps and contact probes of differing sizes. Contact with stainless steel post hardware will skew test results. However, if the only access point is stainless steel, it is OK to test there. It may be helpful for the user to experiment with different battery post design to identify which test contact location provides the best conductance result.

What if I cannot test my batteries directly at the post because of physical constraints?

If battery and cabinet construction makes testing at the post or lead strap impossible, be consistent with every test. If you must test on the hardware,test in the same spot for every cell, every time. If you are inconsistent with your probe or clamp placement,your reading will be inconsistent as well. Typically12-volt batteries are fairly consistent regardless of the point of contact. 2-volt jars can yield greater variance from stainless steel to the lead pad or strap.

What is a Kelvin Connection and why is it needed for accurate conductance measurement?

Kelvin connection refers to any four-point connection electrical test interface. This technique provides for both a test signal injection and a detection circuit. It provides an electronic method to reduce the affect of the variable resistance of the test interface. It is used to ensure the most accurate conductance measurements possible.

Does battery temperature affect conductance measurement?

High temperatures make the conductance test result increase and cold temperatures have the opposite effect. However, Midtronics testers have a built-in temperature compensated algorithm to prevent an error due to temperature. Most battery performance data is calculated at an optimal battery operating temperature of 77° Fahrenheit (25° Celsius). An infrared temperature sensor is a standard component with the complete Celltron test kit to accurately determine battery temperature and is also available from Midtronics as an accessory.

How does the CELLGUARD System communicate?

CellGuard communicates through its Base Coordinator module via a network connection to a server hosting the companion CellTraq software. Alternatively, the system can communicate via serial connection directly to a local PC that has been loaded with the CellTraq software.If a network connection is unavailable or if a local PC is undesirable, the system will also work with a GPRS (cellular) modem connected to the internet.

How are alarms/alerts sent from the monitor?

CellGuard, through its companion CellTraq software, sends alerts via email, text message, or SNMP traps. An unlimited number of users can be notified.

Are there any network/firewall security risks will CELLGUARD?

Security was of the utmost concern when the system was designed. As a result, the system communicates only outbound to the network, so that outside malicious interface with the system is impossible.

What network configurations are required?

A static IP address for each Base Coordinator (generally 1 per system, although some systems allow for sharing), the subnet mask, the default gateway and the resident IP address for the CellTraq software (if it is being placed on a network server).

What are the server/PC requirements for CELLTRAQ?

Windows Operating System (Win 2000 or better), Tomcat Web Server software (provided by Midtronics), SQL Server 2005 Database (or Express free version); a CPU of 2.6 GHz or above and8 GB of RAM is recommended.

Does the system offer alternative communication options like SNMP, MODBUS or Binary Contacts?

The current system, through use of the CellTraq software, can communicate using SNMP traps. A future release of the Base Coordinator module is in process that will integrate MODBUS and Binary Contacts for alarms.

What do the Sensor LEDs indicate?

Sensor LEDs indicate the sensor status including error conditions. Normally, the STATUS LED will pulse green to indicate an idle condition. See the installation manual for more details.

What do the Base Coordinator LEDs indicate?

The POWER LED indicates that power is applied, STATUS LEDS indicates test status, the RFXD/RD LED indicates RF and RS232 transmit data activity, and a blinking RF-LNK indicates that the Ethernet connection is active.

What do the VTC LEDs indicate?

POWER LED indicates that power is applied, and STATUS LEDs indicate test status including error conditions. See the installation manual for more details.

The CELLGUARD Sensors have vent openings. Does this present any risk with flooded or vented battery systems?

No. The concentration of acid fumes in the vicinity would need to be at a level beyond safe for there to be any impact to the sensors—making this concentration a much larger concern than the sensor operation. The normal levels generated by both flooded and VRLA batteries will not have an impact on the sensors. However, the sensors, like any electronic component,should not be directly exposed to spilled liquids, including electrolyte during a refilling or specific gravity testing process. The sensors are “hot swappable”, so they can be disconnected during this process and reconnected immediately following for an added measure of protection.

Is the system UL listed? What other certifications does it hold?

Yes, the high voltage component of the system has received a UL listing. The system has also been certified to CE and FCC standards.

Has the wireless communications architecture been tested for consistent performance even in hostile and congested wireless environments?

CellGuard is designed to operate in extreme environments, and CellGuard has a track record on providing accurate battery health information in both hostile and congested wireless environments.In fact, CellGuard components have operated for more than one year in a hostile 40 battery cabinet with hazardous and extremely high switching noise. Additionally, CellGuard wireless technology is designed to co-exist with Wi-Fi networks. For example, multiple CellGuard Systems have successfully operated in areas serviced by Wi-Fi Access Points.

What is the fuse protection of the system in case of a short?

Both the VTC string monitor and sensor are fused to protect battery plant from any short circuit conditions.

How are the 2V and 12V sensors identified?

The serial number contains a product code which is 02 for a 2V sensor and 12 for a 12Vsensor. The sensor serial number has ten digits, the first four for the date, the next two for the product code, and the last four digits for the sensor serial number.

Can a sensor be reused for another installation?

Yes, a sensor can be reused after the SETUP push switch is depressed for longer than five seconds, which forces the sensor to the original factory settings.

What is the power consumption of the CELLGUARD Sensors?

During "idle" mode, the sensors consume less than 1 Watt.

Can the CELLGUARD sensors accurately measure high capacity 2V flooded cells?

Yes, the Cellguard sensors use the same proven conductance measurement technology and circuitry as Midtronics hand held testers. The sensors connect to each cell via custom terminals with a Kelvin connection for precise and repeatable measurements.

Is monitoring in real time?

Monitoring time intervals are customer programmed. Typically, voltage and temperature monitoring is set at four hour intervals, and the conductance testing interval is set at seven days. CellGuard monitors for a discharge condition one a second.

What are the discharge capture time limits?

Discharge information is captured once a second for the first five minutes and then after five minutes the capture interval is increased to ten seconds. Up to 64 thousand samples can be captured during the discharge event.

What parameters are captured during a discharge event?

Voltage and temperature information is captured for the sensor. String voltage and current information is captured for the VTC unit.