APPARATUS FOR DIAGNOSING BATTERY FOR AUTOMOBILE

PURPOSE:To reduce the cost of the title apparatus, by detecting the operation state of an on-vehicle electric load and judging the quality of a battery on the basis of the internal resistance of the battery calculated from the detection result. CONSTITUTION:The operation state of predetermined on-vehicle electric load 2 is detected by a detection means 3 and current consumption is operated from the detection result by a current consumption operating means 4. The current consumption of the means 4 and the battery voltage due to the means 3 are inputted to an internal resistance operation means 5 to operate the internal resistance of a battery 1. Subsequently, the quality of the battery 1 is judged on the basis of said internal resistance by a judging means 6 and, therefore, a current sensor necessary as a diagnostic apparatus becomes unnecessary and the cost reduction of the apparatus can be achieved.