All cells, whatever their chemistry, have an intrinsic
internal resistance of a few milli-ohms. It is the value of
this ESR (Equivalent Series Resistance) which will determine
the cell’s ability to deliver current to the load without
the battery voltage falling to impractical levels. The unit
measures the ESR value of the cell at the chosen current, by
subjecting the battery to an accurately controlled current
pulse for a few milliseconds, measuring the current, the
off-load and on-load voltages and processing the results to
give the three readings.
The readings (for the chosen current) are:-
% of energy going to the load
Power going to load in Watts.
Power lost in battery heat in Watts
The actual value of ESR in milli-ohms or battery
voltages on-load or off-load are not displayed as they are
academic to the user. They can all be calculated simply and
easily from the displayed results if required.
Displaying the first item as a percentage allows battery
packs of different voltages to be directly compared. It also
allows the comparison of a NimH battery with a Lithium
Polymer battery, for example.
