Q1. Can we measure impedance for each battery in the system?
A. Yes. We do measure the impedance of each battery. See the LifeLink® System Manual, Sec. 3.2.2.5 for complete details.

Q2. Can we measure impedance for the entire string?
A. Not at this time. However, using the System Voltage probe with an AC filter, this might be implemented.

Q3. Can we measure resistance between the batteries? (On the mechanical jumper straps)
A. The simple answer is yes, however, it requires further explanation. LifeLink® measures resistance between points where the battery probe is connected. If the battery probe is connected between, say the positive terminal of one battery and the positive terminal of the second battery, the total resistance will include also the resistance of the strap between the negative terminal of the first battery and the positive terminal of the second battery. Connecting the battery probe across the battery terminals will only measure the resistance of this particularly battery.

Q4. How can we set the impedance baseline (milliohms) and the alarm threshold for impedance measurements?
A. The impedance baseline is the threshold set by customer and is independent from any other parameter of the system. Typically this value is set based on known impedance of the new battery, for which the user or the manufacturer might have his/her own pre-defined criteria of impedance increase that constitutes a faulty battery. For example, one number we have seen used is 15% of the new battery impedance; e.g., if the new battery impedance is 3.5 milliohms, the impedance baseline can be set at 4.0 milliohms. In this case if any battery in the system recorded in the Measurement log exceed the 4 milliohm threshold, a Major or Minor alarm could be originated.
In all of the systems we are shipping now, this impedance alarm reporting function is now disabled, so you will not see this even if you will activate the alarms. We have had number of discussion with different customers regarding their definition of impedance alarms, and we have heard as many different definitions. Since the results of impedance measurements are presented in Table form in the Measurement Log, we’ve left it up to customer to use this data, which is typically graphed and trended over time. However, this function is in software and can be activated easily as soon as the methodology of impedance measurements are agreed on by the industry. We can also customize the application for a specific customer on request.

Q5. How is battery impedance calculated? What are the critical parameters?
A. The impedance in the system is calculated using the AC current, measured by the string current probe, and the AC voltage drop across each battery, measured by the battery probe. The AC current uses a Shunt Current value as programmed thru the Site Configuration screen, therefore, any change in this value will change the impedance reading as well. As an example, if the Shunt Current Rating is changed from 100 Amps to 200 Amps, the impedance value will be half of that at 100 Amps. The Shunt Current Rating has to be set based on the range of the sensor used. . The optimum parameters are 2-5 mV rms AC voltage drop across the battery and 1-6 amps for the current. We have preset the AC current at 1.4 Amps rms, but this can be changed if required.

Q6. How do impedance measurements work? How much A/C current is injected into the system, and for how long?
A. The AC current is injected thru the positive and negative rails of the system. The value of this current depends on the size of the batteries under test. The principle is such that AC current should cause at least a 1.5 - 2 mV AC voltage drop across the battery in order to be effectively measured.

As an example, for batteries with 1.5 milliohms impedance, 1 Amp RMS is enough, however, if we are dealing with large flooded batteries which have impedance of 0.1 milliohms or less, there has to be at least 15 Amps RMS injected. This is due to noise of the charging system, as well as taking into the account that part of the AC current can bypass the battery string. In order to compensate for that, typical current injected into the battery system is about 50% more per system. The total noise voltage might be the number of batteries per string times 1.5-2 mV. This is an insignificant value, since it is below the noise specification of most of the rectifiers.

We emphasize that the AC current is not injected continuously, but only during the impedance test. The duration of the injection is

5 sec + number of batteries per string x 200msec

e.g., for a small system consisting of, say, 20 batteries, the AC current is injected only for approx. 9 sec. However, a large 186 battery system might have this time in the range of 45 seconds. The test is performed once a day automatically or on demand. The customer has option to program the test interval for up to 30 days time period between the tests.

B. Alarms

Q1. How long does the system wait before sending an alarm, in order to assure that the alarm is "real" and not some transient disturbance?
A. The alarm has to appear three times before is declared as valid. Therefore, the answer is three cycles. In the presented example of 2A, with 24 probes, it will be 15 seconds.
Q2. What is the time delay before generating an alarm once an out of tolerance/threshold condition is recorded?
A. The worst-case delay is the number of battery probes multiplied by 200 ms. In the case of 24 battery probes, the delay will be approx. 5 seconds.

Q3. How can alarms be transmitted to a higher level alarm management system?
A. Alarms can be transmitted as a dry contact closure to any higher-level alarm management system. We are currently implementing this functionality with the Element Management System R4 by Advanced Fibre Communications, and with MOSCAT by Motorola.

C. Logs (Historical Information)

Q1. What is the duration of the Alarm Log History?
A. The Alarm Log will collect the alarms and once filled, the Log will work using the FIFO approach, in other words, first in first out. Any new data will erase the oldest one recorded. The Alarm Log capacity is approximately 1500 entries, however, once 80% of the Log is filled, a message will appear on the screen to alert the user.

Q2. What is the capacity of the Discharge Log history?
A. The Discharge Log is located on the PC, so every time the discharge process is completed, the discharge data is dumped on the PC and Discharge log on the server is erased. If, at any given moment, the PC is not connected, the new discharge will erase the previous data. Therefore, the server will always have last discharge.

Q3. What is the capacity of the System Measurement Log?
A. The Measurement Log capacity is 7 Logs. Once the Log is filled, the new data will erase the first recorded. Note: the system measurement snapshot interval can be pre-set from 1 to 30 days. Therefore, the time period covered by this data can be from 7 days (for update interval equal 1 day) to 210 days (for Update Interval equal 10 days). The present software release does not have the capability to preset the update interval for less than a 1-day period.

Q4. What are the readouts displayed on the LED display of the Lifelink 600 Server?  What do they mean?

                      Display                   Meaning (unit)

(1.)                “SV”            System Voltage (Volts – “V”)

(2.)                “AT”            Ambient Temperature (User configurable)

(3.)                “TC”            Total Current (Amperes – “A”)

(4.)                “S1”            String Current (First String) (Amperes – “A”)

(5.)                “S2”            String Current (Second String) (Amperes – “A”)

(6.)                “S3”            String Current (Third String) (Amperes – “A”)

(7.)                “TD”            Total Number of Discharges

D. Terminal Software

Q1. Can the Terminal Server poll the LifeLink® 600s automatically?
A. Not on the current version of software. This feature is included as a requirement in our next Release (4.0) of Terminal Software.

Q2. What is required to host the Terminal Software?
A. The Terminal Software can run on any Windows based PC. Many customers run the software on a centralized desktop system and on field laptops for direct connection to the server.

Q3. How can the LifeLink® server communicate with the Terminal Software?
A. The LifeLink® server has an RS232 output, which can communicate with the Terminal Server via a modem or TCP/IP connection, using landline, cellular, or satellite transport. It can also communicate via a direct connection a laptop or PC on site, using an RJ45 to DB9 cable.

Q4. Can the Terminal Software and the LifeLink® server work together without any batteries connected to the system?
A. Yes. Once you start-up the software, pull down "Site tool" menu and
log onto the system thru "Site manager". After that, again click
on "Site Tool", select "Get Configuration" and, once configuration
is downloaded, select "Modify Site setting". In "System Setup", set
Battery Probes as 0 and Current Probes as 0. This will let you
start the system only on the internal System Voltage probe.

Q5. Do I need to monitor all batteries in a string or in a system?
A. No. Full modularity of the system allows users to save the cost of battery probes by choosing to only monitor some “pilot” cells.

Q6. What higher level management systems can the Terminal Software communicate System Measurement logs and reports with?
A. We are currently implementing connectivity with ProcessNet by Matrikon. We have plans to also implement connectivity with NetBoss by Harris, and Metasys by Johnson Controls. Prioritization of these features is driven by customer demand.

E. Operations

Q1. Does the function of System Measurement cause grounding?
A. No. The LifeLink® Server has an isolation transformer to prevent grounding.

F.  Float Current and String Integrity

Q1.  Your brochures say that you measure Float Current.  How do you do this?

1. (1) The customer can purchase or we can provide a Multitel Float Charge Current Probe (FCCP).  We can interface the output of this third party sensor to our FCCP probe (ESP-FCCP).  This probe provides an analog, signal-conditioning front end for the Multitel sensor, but has no AC current measurement capability.  Due to lack of customer demand, this product (the ESP-FCCP) is currently not being manufactured. However, it could be re-instated if sufficient demand surfaces.

(2) We are constantly exploring compatibility with other commercially available and still in development float current sensors from other third party sources.

(3) Our current sensors (LEM and other third party transducers) provide accurate measurement records of string current during both float and discharge/charging conditions. However, our focus is on measurement of the string current under discharge and charging conditions. While these float current measurements are not as accurate as achieved by a third party FCCP sensor, when combined with our impedance measurements and voltage measurements, trended over time, they provide an excellent set of data that can be used to determine battery state of health.

Q2.  Do you regard float current measurements as indicative of battery state of health?

1. A float current probe might bring some information regarding battery state of health (SOH); however, it might be a redundant solution if used in conjunction with periodic impedance tests, trended over time. If an increasing trend for float current is observed, it is an indication that there is something definitively wrong with the batteries within this string. But this might be due to progressive battery failure, but it may also be simply due to battery ageing (in most of the cases).

Q3.  What is string integrity?

1. Integrity of the entire string also involves inter-battery straps, connections to the posts of the battery, and/or battery sudden failure (short or open). In these cases, the float current probe will not add much information, because this type of failure will not cause float current to increase (except, perhaps, in the case of single cell failure). For a customer interested in string integrity, use of a Float Current Probe to detect a shorted cell might be too costly of a solution. An impedance test will detect the battery problem in any case, whether it is short or open. In the case of an open string, which in fact might be also due to a bad connection, the impedance feature will detect this immediately via an impedance error during Measurement Log test.