Support for the BITE5 battery tester

For accurate ohmic measurements, we recommend that you perform a zero adjustment when changing probes. A zero bar is included with the unit. Select the “Configuration” icon on the bottom of the left column main navigation. In the “Meter” screen, click on 0-Adj located at the bottom right to perform the procedure. For further details, refer to the “Configuration of BITE5” section of the BITE5 user guide.

When performing an impedance test, or any ohmic test, the batteries must be fully charged. An impedance test is a relative test that compares a present measured value to past values. If the battery is not fully charged, then the measured value will not be the same as it would in the battery’s fully charged state. Therefore, you cannot compare such a value to past values because there is no common state of charge of the battery. 

Note: With the BITE5 there is a special impedance test that can be performed while the battery is undergoing a discharge test. This will allow the operator to trend the cell impedance values throughout the process and establish alarm limits for the string. See: “Performing an impedance and discharge test (special testing)” in the user guide for further details. 

Momentarily press and release the “Power ON/OFF” button. The displayed screen will be saved to the SD card as a bitmap file. The bitmap will be located at the following path: \MEGGER\PQA\SNAPSHOT

The IEEE recommendations say that a 50 % to 100 % change from the baseline on a cell is serious and warrants further investigation, but it’s important to take into account the criticality of the application and battery type. VLA and VRLA batteries fail in different ways. The typical failure mode for a VLA cell is positive grid corrosion. When a VLA cell fails, it fails in shorted mode, which means that current can still pass through it. This means that series strings can be used even in critical applications. VRLA cells, however, most often fail due to drying out and they fail in open mode, which means that they may not be able to pass current. In critical applications therefore, they should be used in parallel. With these differences in mind, a 50 % to 100 % change from baseline is a good screening criterion for VLA batteries, but with VRLA batteries you may want to consider being a little more cautious and use 20 % to 30 %.

You’re actually doing an overall discharge test of all the cells and it’s inevitable that some will reach the end voltage – let’s say this is 1.75 V – earlier than others. You shouldn’t stop the test when one cell reaches 1.75 V, you should stop it when the average cell voltage is 1.75 V. At this point, some cells could be at 1.8 V and others at 1.6 V. Monitor the overall battery voltage during the test and, if you have for example 60 cells, stop the test when the voltage reaches 60 x 1.75 V = 105 V.

In reality, float voltage measurements are of limited value. They can be used to confirm that the charger is working, but they give no information at all about the battery's state of health. Measuring the float voltage of a cell will also show whether or not it is fully charged, but it is important to remember that, just because a cell is fully charged, this doesn’t mean that it will deliver full capacity. It is by no means unusual for a battery that is close to failure to have a float voltage that is within acceptable limits. A low float voltage may indicate that there is a short in the cell. In a lead-acid battery, this should be suspected if the float voltage is 2.06 V or less, assuming that the charger is set for 2.17 V per cell. In other cases, a cell may float at a considerably higher voltage than average. This may be because the high float voltage cell is compensating for another weaker cell that is floating low. It is also possible for one cell to float high to compensate for several cells that are floating a little low, because the total of all the cell float voltages must always equal the charger setting.