Batteries are electro chemical devices and are not resistors. When a battery is on float charge and current is passing through the cells, causing very small, but continuous fluctuations in the electrical state of the jar, from capacity to state of charge. These chemical reactions along with additional factors such as changes in temperature, rectifier outputs, and battery state-of-charge may all contribute to variations in conductance measurements from week to week. Since Midtronics conductance measurements are extremely sensitive due to the nature of the digital signal processing, the measurements will detect these minor electrical changes in the battery.
Based on the Cellguard hardware design specifications a 2% variation in conductance measurements from week to week is acceptable. When you add in the above factors, during normal conditions, a 5% variation in conductance measurements should not be cause for alarm. If there are variations in conductance measurements greater than 5% from week to week then you need to investigate further to identify if the measurements are varying due to system issues or environmental issues. A trend review is very helpful in assessing the change. The Celltraq Enterprise Software makes it very simple to conduct this trend assessment.