Battery internal resistance measurement is a reliable procedure for battery condition assessment that is done within seconds. Combined with cell voltage and intercell connection resistance measurement, the test determines the state of health of batteries.
Internal resistance represents the battery’s limiting factor to deliver the required current and/or supply the required energy. High internal resistance results in increased heat generation in the battery under load, i.e unwanted energy loss. Furthermore, high resistance implies a higher voltage drop on the loaded battery. This will speed up reaching the battery cut-off voltage and triggering an early shutdown.
Most important of all, high resistance will reduce the amount of energy the battery can supply within its operating voltage. As a result of that, the battery capacity will be reduced.
Although internal resistance measurement does not determine battery capacity, it is a reliable parameter indicating the aging pace. A user can compare old with the new measured values to keep track of changing trends.
Since battery resistance is temperature and state-of-charge dependent, measurements should always be taken under the same conditions of temperature and charge level.