DC / AC Resistance Percentage

Units: [%]

In some batteries, the DC Internal Resistance can be significantly higher than the AC Internal Resistance due largely to the amount of capacitance in the battery. Every battery has capacitance, though some will have more than others due to how the chemistry is designed. As a result, the DC resistance can usually be expressed as a multiple of the AC resistance.

The BMS observes the AC resistance of the battery and calculates the DC resistance from the AC resistance based on this parameter. A value of 1 or less (eg: 0) is ignored and the AC resistance is assumed to be the DC resistance as well.

This parameter allows for the user to program in the correlation between the AC resistance and the DC resistance in terms of percentage. If the percentage is not known, it can be determined by comparing the resistance observed from a battery under constant load for 1 second to that of it under constant load for 10-20 seconds.

Example: Suppose that the AC resistance of a given battery is 2 mOhm and the percentage for this parameter is set to 120%. The DC resistance would then be 2.4 mOhm as that would correspond to 120% of the AC resistance value.

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