THERMAL MANAGEMENT
www.electrichybridvehicletechnology.com // January 2020 // 55
“If a manufacturer uses simple battery
management systems that do not pay attention
to that, the battery can either overheat or be
charged at too cold a temperature. If the
battery management system is programmed
in the wrong way, or is too simple, it will not
meet European standard and it can happen
during regular charging. This has nothing
to do with the material itself – it’s related
to how the cell is manufactured, and if
the battery management system is
intelligent enough.”
Keeping cool
Cell temperature can also be di cult
to control with faster charging speeds.
According to Gael Chouchelamane, chief
engineer, battery systems at Ricardo,
ultra-fast charging (UFC) generates 15-18kW
of heat, compared to 3-4kW under normal
driving conditions. In turn, this makes
air-cooling inadequate, so manufacturers are
introducing more sophisticated measures to
keep the maximum cell temperature under
50-55°C (122-131°F) during peak operation.
Above this temperature, the electrolytes can
vent as a gas, and the cell itself can break
down. This is becoming harder to manage.
“Approximately 5% of the pack cost is
represented by the battery thermal system,”
says Chouchelamane. “This is likely to increase
in the future with new requirements such as
ultra-fast charging. Improved performance of
cold plate using ethylene glycol is mandatory
but has limits, and it is likely therefore that
thermal engineers will increasingly opt for
direct immersion cooling of the cells.
“Once the heat has been extracted from the
battery pack, it needs to be dissipated to the
ambient air. To achieve this, the airconditioning
system will be under high
demand during UFC and will require
upsizing of the evaporator cooling the
fl uid that cools the battery, in parallel
with uprating of the air-conditioning
compressor, condenser and cooling fan.
“Approximately 5% of the pack
cost is represented by the battery
thermal system. This is likely
to increase in the future”
Gael Chouchelamane, chief engineer, battery systems, Ricardo
6. The Mercedes
fully-electric EQC
underwent extensive
battery testing,
including cold chamber
testing to examine
how cells react to
extreme temperatures
6
/www.electrichybridvehicletechnology.com