Patent ID: 8788226

Claim:
A battery tester with high precision, comprising a casing having an input device and two detecting wires, a microprocessor, a variable loading unit and a battery power status detecting unit, wherein: the detecting wires are adapted to selectively connect to two electrodes of a battery; the variable loading unit electronically connected to the microprocessor and connected to the detecting wires; and the battery power status detecting unit is electronically connected to the microprocessor to detect a battery voltage and a battery current of the battery and to report the battery voltage and the battery current to the microprocessor; and the battery tester is characterized in the input device providing different options of CCA B and 1/N CCA, with at least 2 options for N, where N is variable; and the microprocessor storing a strategic decision process and the strategic decision process having steps of: (a) obtaining the battery voltage V B of the battery and reading the CCA B and the 1/N CCA from the input device; (b) calculating an equation of loading resistance with the CCAB, an initial battery voltage and the 1/N CCA to obtain a proper loading resistance for the batter and adjusting a resistance of the variable loading unit in accordance with the calculated loading resistance; and (c) executing a detecting process to obtain a detecting waveform.