Battery Characterization
21
battery's output will violate most operating specifications. Do not leave a discharging
battery unattended.
When the battery is discharged, the Watt's Up display indicates the total charge (Ah) and
energy (Wh) the battery delivered to the load as well as the peak Amps (Ap) and peak
Watts (Wp) used and the minimum voltage on the battery during the discharging process.
Make a note of these final discharge values to determine charger efficiency, battery
capacity and health.
See the Data Queue for Charge (Ah), Peak Amps (Ap), Peak Power (Wp), min. Volts
(Vm) etc.
100.00A
10.00V
Data Queue
1000.0W
Battery Charging Efficiency
Battery Charging Efficiency (BCE) is the ratio of energy put in to energy removable.
Charging Efficiency = Discharge Energy
Charge Energy.
Efficiency is never 100% due to a variety of losses involved. If the charge energy was 15
Wh and the discharge energy is 14.2 Wh the Charging Efficiency is:
14.3
15 = 0.95 or 95%
BCE depends on both the charger and the battery so it can be difficult to determine where
problems are without extra batteries or chargers.
Battery Health
Battery Health is determined by comparing the actual energy or charge capacity with the
manufacturer's specifications or a "new" battery as a reference. Since it can be difficult to
get manufacturer specifications to match test results, it is often simpler and just as useful to
record the capacity value of a "new" battery and save that as a baseline. Note that a "new"
battery may be defective and give out of specification results.
By occasionally discharging a battery pack and comparing the energy delivered to the
baseline value delivered when it was first put into service, you can track that battery's
health. The percentage of baseline capacity at which a battery is considered to be at the end
of its life depends on battery chemistry and how it is used. A reduction in charge capacity
can also be an indication of battery pack damage or imminent failure.
To summarize, the percentage of baseline or initial capacity indicates a battery's health.
Baseline Capacity Ratio = Current Capacity
Original Capacity
8.1.3
Low Voltage Measurement
Watt's Up's ability to measure down to 0 V allows unique measurement scenarios.
For example, if you have a micro model, or a model that uses a single cell or low voltage
battery pack or even solar cells, the Watt's Up can still measure all your system parameters
like in higher voltage systems. Watt's Up's low operating current minimizes the impact its
presence has on low power systems.
To support low voltage measurement, just connect a power source to the auxiliary power
connector.
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual
RC Electronics, Inc.
