TORKEL900 series battery discharge test systems
High discharge capacity
Discharge up to 220 A, offering the possibility to shorten test times. With additional TORKEL units or extra load units (TXLs), higher currents are available.
A complete standalone discharge test system
When used in conjunction with the BVM battery voltage monitor, the TORKEL will measure battery capacity as well as individual cell voltage data throughout the entire discharge test.
Real time monitoring of test results on screen
With BVM connected you can spot weak cells and prepare in case they need to be bypassed to continue test.
Eliminate the disruption of taking the battery out of service, discharging, re-charging, and returning to service, no need for a backup battery bank.
Safety in all details
Automatic detection of blocked airflow to prevent overheating, spark-free design, and emergency stop all contribute to make sure the discharge test is performed as safely as possible.
About the product
The TORKEL900 series of battery discharge test systems are Megger’s fourth generation of battery discharge analysers. Discharge testing is the only test method that provides a comprehensive insight into battery capacity, and is therefore an essential part of vigorous battery maintenance programmes.
Tests with the TORKEL900 series can be conducted at constant current, constant power, constant resistance, or in accordance with a pre-selected load profile. What’s more, if you connect the BVM battery voltage monitor to a TORKEL900 unit, the TORKEL becomes a complete standalone discharge test system.
With the TORKEL900 series, you won’t need to disconnect the battery from the equipment. The TORKEL900 units use a DC clamp-on ammeter to measure the total battery current while regulating it at a constant level. If the voltage drops to a level slightly above the final voltage, the TORKEL issues an alarm and if there is a risk of deep discharging the battery, the TORKEL stops the test. All results are stored in the TORKEL and can easily be transferred to a PC via a USB drive.
Additionally, testing times are much shorter with the TORKEL900 series, thanks to their high discharge capacity. Discharging can take place at up to 220 A, and if higher current is needed, two or more TORKEL units or extra load units (TXL) can be linked together.
The TORKEL900 series has three models available: 910, 930, and 950, depending on the maximum current (up to 220 A), voltage (up to 500 V), and functionality required.
- Data storage and communication
- Internal memory
- Data storage and communication
- Power source
Product documentsAdditional documentation can be found on the support tab
FAQ / Frequently Asked Questions
IEEE Recommended (Maintenance) Practices cover the three main types of batteries: Flooded Lead-acid (IEEE 450), Valve-Regulated Lead-acid (IEEE 1188) and Nickel-Cadmium (IEEE 1106). Generally speaking, maintenance is essential to ensure adequate backup time. There are differing levels of maintenance and varying maintenance intervals depending upon the battery type, site criticality, and site conditions. For example, if a site has an elevated ambient temperature, then the batteries will age more quickly implying more frequent maintenance visits and more frequent battery replacements.
Yes, with the optional CT, the TORKEL will automatically sense and regulate the discharge current even when the batteries are connected to their normal load. Most users choose to make an 80 % discharge test if the battery is to remain on-line, thereby ensuring that there is still some backup capability remaining at the end of the test.
A load/discharge test is the only definitive way to assess a battery’s capacity. When used regularly, discharge testing can be used for tracking the battery’s health and actual capacity and estimating the remaining life of the battery. During the test, we measure how much capacity the battery can deliver (i.e., current multiplied by time, given in Amp-hours (Ah)) before its terminal voltage drops to a level signifying that the discharge is complete. This terminal end voltage equals the battery cells’ end of discharge voltage x the number of cells. For example, suppose the end cell voltage is 1.75 V, and the battery has 60 cells. In that case, the test stops when the terminal voltage reaches 60 x 1.75 V = 105 V. Throughout the test, the current is maintained at a constant value. If the battery reaches the end of discharge voltage at the same time as the specified test time ends, then the battery’s measured capacity is 100 % of the rated capacity. Conversely, if the battery reaches the end of discharge before 80 % of the specified test time has passed (e.g., within less than 8 hours of a 10-hour specified time), you should replace the battery.
At least a couple of times during the discharge test, you must measure the individual cell voltages. The most critical time for these voltage measurements is at the end of the discharge test to find the weak cells. It is also imperative that the time, or the current, during a discharge test is adjusted for the battery’s temperature. A cold battery will give less Ah than a warm one. Temperature correction factors and methods are described in the IEEE standards.
Batteries can also be tested in a shorter time than their duty cycle, for instance, in 1 hour. If you elect a reduced test time, the current rate has to be increased. The advantage of this approach is that a battery’s remaining capacity is greater at the test’s conclusion than that for a full-length test. A battery with less capacity is inconvenient and possibly very expensive to rectify in time, resources, and money.
Battery systems are designed to provide backup supplies during power outages. Since a discharge test is nothing other than a simulated power outage, there is no risk of battery damage. Batteries can normally be deep discharged (that is, discharged to the manufacturer’s end-of-discharge voltage) between 100 and 1000 times, depending on the type of battery. Using a few of these discharge cycles for capacity testing has a negligible effect on overall battery life. Nevertheless, there is no reason to carry out discharge testing more frequently than recommended by the relevant standards.
Further reading and webinars
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There are two main causes:
- Temperature compensation is enabled and you have not entered a battery/ambient temperature.
- The TORKEL is not detecting the battery.
What you can do:
First check to see if the temperature is set on the TORKEL; if not, make sure to enter the temperature. Otherwise, verify that all battery cables are firmly connected.
Check to make sure that nothing is blocking the fans. The fans also rev up to maximum speed when the “Emergency Stop” button is pressed; check and release the “Emergency Stop” button if needed.
The maximum power consumption that the TORKEL can provide is 15 kW, so the maximum current draw depends on the battery voltage. Check to make sure the current value you set is not too high, given the battery voltage. You can confirm the maximum possible current by checking the data sheet, user guide, or the “TorkelCalc” tab in the Torkel Viewer software. If this message appears when using multiple units together, you can ignore it if it does not appear on the primary unit controlling the test.
Under the “Settings” tab in the TORKEL, verify that you have set "Current measurement" to "External" and that the ratio is set correctly for your CT. The mV/A ratio must match the ratio on the DC clamp-on current probe itself. If you are using the optional 1000 A DC clamp-on probe from Megger, enter 1 mV/A.
If you are still not getting any readings, check to verify the CT is turned on or cycle the on/off switch. Additionally, you can swap out the battery or check all connections if you have the power supply option. If you are getting faulty readings, perform a zero adjustment on the CT.
F1 is a voltage-controlled circuit breaker connecting the TXL Extra Load resistors to the battery. If F1 does not latch or remain at its upper (On) position, verify that power is connected to the TXL and that the unit’s mains switch is turned on. Ensure that you have correctly connected the control leads from the “CONTROL IN” input on the TXL to the “TXL STOP” output on the TORKEL.
Verify that the Data output port of the Power and Signal connector is connected to the BVM1 connection on the TORKEL. Verify the DC IN port and power supply are connected properly. Unplug and reconnect all connections to verify. If you have multiple BVM kits, swap out the Power and Signal connector to verify functionality.
Check the cables of the BVM units and the power supply to the BVM units. If you have multiple BVM kits, swap out the Power and Signal connector to verify functionality. If you have connected more than 61 BVM units, then you need to connect an extra ethernet cable from the last BVM (red alligator connector) to the “To last BVM unit” plug on the Power and Signal connector. Check the BVM connection diagram for reference.
Check the connections from the BVM to the battery cell to make sure they are tight. If a single BVM or only a few BVMs are not displayed, the problem is probably in the connection from the BVM to the battery. If a string of BVMs is not displayed, then it could be a fault in the connections between BVMs. To verify that a BVM is working correctly, switch it with a BVM on another cell that works properly. If the error follows the BVM, i.e., the missing cell now appears while the cell that you moved the suspect BVM to disappears, there is most likely a fault with the BVM, and you will need to replace it. If the error does not follow the BVM and the original missing cell is still not appearing, the fault is most likely in the interconnecting cable, and you will need to replace it. The same swap-out procedure can be performed with the cables to verify their integrity.
Interpreting test results
A capacity test is the only way to obtain a quantitative assessment of a battery’s actual capacity. When used regularly, capacity testing can track the battery’s health and actual capacity and facilitate estimations of the battery’s remaining life. The battery’s capacity might be slightly lower than specified when it is new. This behaviour is normal.
Rated capacity values are available from the manufacturer. All batteries have tables telling the discharge current for a specified time, down to a specific end of discharge voltage. The table below is an example from a battery manufacturer:
|8 h Ah Ratings
|Nominal rates at 25℃ (77℉) Amperes (includes connector voltage drop)
Capacity is represented by current x time (Ah). A capacity test measures how much capacity a battery can deliver before its terminal voltage drops to a value equal to the end of discharge voltage x number of cells. A constant current is maintained throughout the test. You should select a test time that is approximately the same as the battery’s duty cycle, and use the same testing time for future capacity tests throughout the battery’s lifetime. This consistency improves accuracy in trending how the battery’s capacity changes.
Common test times are 3, 4, 5, or 8 hours and the typical end-of-discharge voltage for a lead acid cell is 1.75 or 1.80 V.
If the battery reaches the end of discharge voltage at the same time as the specified test time ends, the battery’s measured capacity is 100 % of its rated capacity. If it reaches the end of discharge at 80 % of the specified test time or sooner (e.g., at 8 hours of a 10-hour test time), you should replace the battery. If the battery reaches the end of discharge voltage after the specified time limit, the battery’s actual capacity is higher than its rated capacity. In these cases, even though the battery has not reached the voltage limit in the specified time, you should continue the test until the voltage limit is reached. Quantifying this extended time is necessary to discover the battery's actual capacity, which is important for trending. Batteries are designed to provide specified capacity until their end of life. Consequently, a battery will generally have a higher-than-rated capacity after it has been in operation for a while and one closer to its capacity at the end of its life. Note: All capacity calculations should be temperature corrected.
User guides and documents
Software and firmware updates
FAQ / Frequently Asked Questions
Yes, a TORKEL can be used as an extra load bank to meet your desired current specifications as long as it is rated for the voltage of your source. To determine the configuration you need, you can put your testing parameters into the Calculator Input section under TorkelCalc tab in the included Torkel Viewer software. Only the primary TORKEL will be used for recording purposes and will be able to adjust its internal resistance value as the source voltage drops. The secondary TORKEL should be set to the same current as the primary TORKEL. You do not need to pay attention to the message reading “Cannot regulate” as long as it does not appear on the primary TORKEL. The user guide contains several examples of how to connect multiple TORKEL or TXL units. Note: When using additional loads, i.e., TORKEL or TXL, a clamp on probe (CT) is required.
The TORKEL has a maximum power consumption of 15 kW; therefore, the maximum current it can draw will depend on the voltage of the source to which it is connected. To make sure your TORKEL will provide the necessary current for your test or to determine if extra TORKEL or TXL units are needed, you can put your testing parameters into the Calculator Input section under TorkelCalc tab in the included Torkel Viewer software. There are also several examples of available configurations of TORKEL 900 and TXLs and their rated maximum current on the data sheet. If you have further questions concerning the proper configuration, you can contact Megger Technical Support. Note: When using additional loads, i.e., TORKEL or TXL, a clamp on probe (CT) is required.
Battery manufacturers’ published discharge times range from 1 to 20 hours or more, but it is preferred to test the batteries in a reasonable amount of time. A performance test with a time duration of 3 to 5 hours is common. Shorter test times require higher loads, i.e., you will need extra TORKEL or TXL units. The initial nominal discharge time is chosen by the operator but the current must be drawn according to this time and the end cell voltage provided on the data sheet. For example, in the Interpreting test results section above, for a DCU/DU-13 battery rated at 150 Ah, the TORKEL can be set to a current of 38 A if we choose a nominal time of 3 hours. If we choose a nominal time of 5 hours, then the TORKEL needs to be set to a current of 27 A. Once a nominal test time is chosen, it should be used for all future capacity tests on the battery for proper trending and evaluation.
You should set the voltage warning and stop limits according to the number of cells and end of discharge voltage. For example, given the cell information in the Interpreting test results section above, you are calculating the end voltage for a 1.75 V end cell voltage. For a typical substation application of 125 V, there will be 60 cells with a nominal voltage of 2.25 V per cell for a total nominal voltage of 135 V (2.25 V x 60). You calculate the voltage stop limit by multiplying the end cell voltage by the number of cells. In this example, you multiply 1.75 V by 60 cells for an end voltage of 105 V. When the battery voltage reaches 105 V, the TORKEL will automatically stop the test. To avoid stopping a discharge test prematurely, we recommend setting no other stop limits, such as for capacity and time.#
Although there are no standard warning limits, Megger recommends a voltage warning limit approximately 3 V above the stop limit, allowing the user to make a few final checks before the test finishes. You can set the warning limits for capacity and time to the nominal values of the battery capacity and the nominal time rate at which you chose to perform the test. Finally, setting the BVM or cell warning limit to the end cell voltage, e.g., 1.75 V, will allow you to monitor weak cells and warn you if any connections are removed. Note: When the battery voltage reaches 105 V, several cells will be below 1.75 V, and others will be above 1.75 V. This behaviour is expected.
Yes. If you bypass a cell or multiple cells, you need to adjust the end voltage limit on the TORKEL to account for the missing cells. For instance, in the example provided in the FAQ, "What are the recommended warning and stop limits?" you have an end voltage of 105 V (1.75 V x 60 cells). Suppose you need to bypass two cells. You must change the end voltage to 101.5 V, which equals 1.75 V (end cell voltage) x 58 cells (remaining cells in the string). Make sure to adjust your voltage warning limit as well.
The leads for the TORKEL 910 are rated for a maximum of 110 A. As long as you stay within 110 A, you can use them on the 930 and 950 models. If you need to use higher currents, then you need to use the cables provided with the 930/950 models. There is an option of a clamp-on cable set for the 930/950 models that will handle the higher current.
Megger provides two types of cable sets, one with a fork connection and one with a clamp. The cable with the clamp is easier to use and connect to the battery, assuming there is room for it. The fork connector is more secure than the clamp connector, but its use means you must loosen and retighten the nuts on the battery bank. As long as the cable is rated for the amount of current you want to draw, you should use the cable set you prefer.
This is due to the resolution setting in Torkel Viewer.
Yes, you can combine or mix and match parts from different BVM kits. If more than 61 BVM units are connected, you need to connect an extra ethernet cable from the last BVM (red alligator connector) to the “To last BVM unit” plug on the Power and Signal connector. Check the BVM connection diagram for reference. You can use up to 121 BVM units (120 cells) with a single Power and Signal connector. If using more than 121 BVM units (more than 120 cells), you must use an additional Power and Signal connector that you will connect to the BVM 2 USB port on the TORKEL. Refer to the user guide for connection diagrams. WARNING: The max battery string voltage must not exceed 300 V, or Opto couplers will be required. With the optional Opto couplers, you can test a max battery string voltage of 500 V.
In short strings (less than 40 cells), we advise replacing the entire battery when between three and five cells have been changed. You should replace the battery for longer strings when more than 10 % of the cells have been changed.
Yes, with the optional CT, the TORKEL will automatically sense and regulate the discharge current when the batteries are connected to their normal load. Most users choose to make an 80 % discharge test if the battery is to remain on line, thereby ensuring that there is still some back-up capability remaining at the end of the test.
The battery should be on float voltage for a minimum of 72 hours prior to a discharge test. Some battery manufacturers recommend equalising the batteries prior to testing as well. If the manufacturer recommends equalising the battery, equalise first and then leave on float for at least 72 hours before performing discharge testing.