Automotive Engineering - June 2023 - 28

A connected approach to
AUXILIARY
BATTERY
CONTROL
Vehicle electrification
and increasing
electronic content as
shown in this 2024
Lincoln Navigator are
putting significant load
demands on the 12V net.
An 'intelligent' systems strategy ensures that an electrified vehicle's auxiliary
battery has enough energy to meet basic loads, whether the vehicle is running
or in park.
by Vivek Kumar
A
s vehicles become electrified and more " intelligent, " the
energy consumption of the auxiliary system increases rapidly.
The auxiliary battery, typically a 12V unit, acts as the
backbone of the system to support the proper operation of
the vehicle. It is important to ensure the auxiliary battery has enough
energy to meet the basic loads, regardless of the vehicle being in
park or running. However, existing methods only focus on auxiliary
energy management when the vehicle is in a dynamic event.
To fill the gap, an intelligent strategy is proposed that detects a
low state of charge (SoC) condition. The strategy would temporarily
turn down the auxiliary loads based on their priorities and charge the
auxiliary battery at the maximum efficiency. This proposed strategy
would allow the vehicle to make intelligent decisions on charging the
auxiliary battery.
As a result, the energy consumption remains low while the SoC of the
auxiliary battery is sustained. Since the auxiliary load represents an important
part of energy consumption in the vehicle, an optimal energy
management strategy for the Auxiliary Power Unit (APU) is necessary.
The auxiliary system architecture for HEVs (Fig. 1) may vary depending
upon which hybrid architecture is used. When the Auxiliary
Battery Management System (ABMS) detects the SoC of the auxiliary
battery is low, it passes that information to Powertrain (PCM) via the
28 June 2023
Body Control Module (BCM). The PCM then commands
the APU to start converting energy from the high voltage
(HV) battery into the auxiliary battery.
Auxiliary battery load categories
There are various loads applied on the auxiliary battery;
they are classified into six categories (Table 1).
Continuous key-on loads include loads when the vehicle
is turned on. Transient loads represent the loads
that are needed only for a specific event. The loads for
OBD testing are related to the loads used to satisfy
regulatory requirements. The loads for vehicle safety
and performance represent loads associated with safety
and performance, respectively. The continuous keyon
loads differ from the continuous key-off loads because
the amplitude of these loads is generally greater
than the amplitude of these loads during key-off.
This study focuses on two vehicle use cases: the
continuous key-on loads and the continuous key-off
loads. These two categories of loads are selected because
they are more relevant to the APU strategy.
AUTOMOTIVE ENGINEERING
FORD
Automotive Engineering - June 2023

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