An on-line measurement system for internal resistance of battery is developed as an IoT (Internet of Things) device in order to evaluate the effect of pulse generation which is expected to prolong the life of lead acid battery. This system consists of a pulse control sub-system and a monitoring and recording sub-system. The pulse control sub-system generates a controlling pulse with its specified width and cycle. The monitoring and recording sub-system has an SD card drive recording the measurement data for the backup as well as an Ethernet interface transmitting them when measured. The proposed on-line measurement system is implemented by the combination of one-board microcomputer and some peripheral circuits. In the experiments, the internal resistances and the voltages of the battery, temperature and humidity of the air and measured-times are actually measured once every hour for three weeks. The measurement data are successfully recorded in the SD card and are transmitted to the server at the same time. Moreover, the operating status can be checked at any time by way of web browser.