Appendix A: Internal Resistance of Batteries and Battery Aging

Ideally for any source of electricity, it is desirable that the voltage is constant, irrespective of how much power is taken from the source (provided that it is within the capacity of the source). This is usually not the case, particularly for batteries. Available voltage at the terminals of a battery does not stay the same if the current (and consequently the power) taken from the battery varies. As current increases, voltage decreases; in other words, there is more voltage drop in the source. As long as this voltage drop due to an increase in the delivered current is small and acceptable, everything is fine.

Figure A.1 illustrates the decrease in voltage versus the increase in ...

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