Aerospace & Defense Technology - August 2024 - 16

Power Electronics
Battery life depends on these parameters,
so making different battery profiles
that suit specific discharge situations
is essential.
A general-purpose DC source aims to
be a perfect voltage source with no output
impedance by using remote sensing
feedback to maintain its output
voltage constant. However, unlike a
battery, its voltage does not decrease
with load current. Moreover, feedback
regulation is not instantaneous, which
causes voltage drop and overshoot
when loading and unloading changes.
A significant transient voltage drop
can activate a device's low-battery-voltage
shutdown.
When powering a device with a DC
source, emulate the battery's characteristics
for current drain results comparable
to those of a battery. A regular DC
source differs from a battery, but a DC
source that can imitate a battery helps
users get more reliable results. Make sure
the power supply used has a programmable
output resistance.
Voc, Ri vs SoC
4.5
4.0
3.5
3.0
2.5
2.0
100
80
60
40
State of charge [%]
Figure 1. A battery profile using a battery test and emulation software. (Image: Keysight Technologies)
20
Extending Battery Life with
Emulation Software
Using a battery emulator instead of a
battery has several advantages for
device testing:
* Creates a safer test environment: By
using an emulator, designers do not
have to physically charge and discharge
batteries, which can become
dangerous with repeated cycles.
* Achieves repeatable results: Characteristics
of an emulated battery do not
vary from physical batteries, whose
characteristics can fluctuate after
charging / discharging. They can also
vary between different batteries, even
in the same model.
0.090
* Reduces test setup times: Designers can
instantly simulate any state of charge
(SoC) versus manually draining a battery
to the desired level to speed testing.
A battery emulator operates through
0.085
0.080
0.075
several steps. The initial step is to load
a battery profile, which is the data
from a graph of the battery voltage and
internal resistance against the SoC, as
shown in Figure 1. Designers can generate
a battery profile using battery
modeling software or get a profile from
a battery provider.
Creating a profile with modeling softFigure
2. Example of a device's current consumption waveform loaded into an advanced battery test and
emulation software. (Image: Keysight Technologies)
16
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ware will make the profile match the
current consumption for a particular
device, which is more precise than a
generic profile from a battery supplier.
For instance, a generic profile is not
helpful if the battery supplier makes the
profile based on a steady current draw
when the device under test has a variable
current consumption. Figure 2 shows a
battery profiler with a current consumption
profile from a device loaded into it.
The software repeats the waveform until
the battery runs out of power.
The next step is to choose the initial
SoC and the termination voltage. Designers
will link the device to the emulator
and begin the battery emulation with
software. Battery emulators constantly
monitor the current, whether charging or
discharging, to dynamically compute the
emulated SoC. The emulator continually
adjusts its output (voltage and resistance)
according to the SoC to match the loaded
battery profile. The test finishes when the
emulator reaches the termination voltage
if the emulator discharges.
Aerospace & Defense Technology, August 2024
Voc [V ]
Ri [ohm]

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Aerospace & Defense Technology - August 2024

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