When the battery is charged and discharged, its internal resistance expands. When the battery is charged and discharged to a certain level, the change in internal resistance is significant. When the battery is fully discharged, its resistance is 25 times larger than when the battery is fully charged. Battery temperature also interferes with accurate measurements of internal resistance, but only significantly below icy degrees. Below 32°F, temperature interferes significantly with internal resistance, and at -20°F the internal resistance is twice as high. This is why the power of the battery is much smaller in winter. The battery's use time will also affect its internal resistance. The longer the battery is used, the greater the internal resistance. How much the internal resistance increases is related to the application and maintenance of the battery. .The overall condition of the battery (such as invalid mechanical equipment) will also interfere with the internal resistance of the battery. Some failure modes will increase the internal resistance of the battery. Let's take a look at the basic working principle of the battery internal resistance tester.

The battery internal resistance tester is obtained according to many experiments: the internal resistance value of the battery increases with the decrease of the battery volume. In other words, when the battery continues to age and the volume continues to decrease, the internal resistance of the battery will continue to increase. According to This kind of experimental result can be obtained, according to comparing the internal resistance value of the whole group of batteries or tracking the internal resistance transition level of a single battery, the outdated batteries in the whole group can be found, and by tracking the internal resistance transition level of a single battery, it is possible to grasp the battery's internal resistance transition level. Aging level, to achieve the purpose of maintaining the battery.

For the battery, if the internal resistor is increased by more than 20% from the reference value (average value), the battery characteristics will be reduced to a lower level. This value is also proposed by IEEESTD to take corrective measures (charge and discharge experiments or replacement) immediately. The specification for IBEX1000 then sets the alert value to 20 percent based on this proposed standard.