TORKEL900 series battery discharge test systems

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.