The Assessor Mag Autumn 2024 Web - Flipbook - Page 31
The constraint is the battery height.
This literally reduces passenger
compartment volume.
Early pure electric drive ‘conversions’
were SUVs, where the skin allowed a
shorter passenger compartment length
with signi昀椀cant additional compartment
height, and then use the quasi-off road
ground clearance to accommodate
the battery pack – thus maintaining
road car ground clearance for a vehicle
which looked like an SUV. The 昀椀rstgeneration Mercedes-Benz EQC is a
clear example of this.
BMW were the 昀椀rst to achieve a
110mm overall battery pack height
from the lower to upper case in the
The traction battery can reach right
across between the sills – but is not
very tall. The image is of the Mini
Countryman BEV U25 traction battery
assembly, showing the aluminium
extrusions which sit behind each
sill. The primary protection is from
the body shell, but the aluminium
extrusions protect the battery modules
and ultimately, the battery cells inside
those modules.
region of the occupant footwells with
the i4 G26, technology that has been
subsequently rolled out for other BMW
Group pure electric drive models.
Unlike the shallow front under昀氀oor
fuel tank of Honda Jazz, such a battery
pack does not suffer from liquid surge
while driving, but it does cause other
problems.
Think back to your 昀椀rst mobile phone,
and the small battery. It was easily
the biggest single part, and in time,
the most valuable part too. Each
generation of phone sought to reduce
the size and weight of the battery,
while increasing device life for a given
charge. Vehicle traction batteries
have gone through and are still going
through evolution.
Inside the battery case there are
modules (boxes) which contain cells.
Those modules sit on heat transfer
plates, which are there to remove
excess heat (cooling) or to add heat if
required. Remember a battery has a
minimum and maximum operational
temperature regardless of use mode.
In addition, there is the internal
harness, internal thermocouples,
tubes to carry coolant / refrigerant and
the all-important battery condition
control module. Sometimes part of the
external charger is inside the battery
pack:
Here’s the traction battery 昀椀tted to i4 G26.
This is the assembly of the Mini Countryman BEV U25 powertrain, showing the traction battery height.
Consequences
Should a vehicle with a large traction
battery suffer impact damage and at
some point, have ground contact, there
is not much vertical space inside the
battery case to accommodate impact
deformation. Further, if we can see
marks or grooves in the lower battery
case, remember this is after plastic
deformation of the material – the
impact dynamic deformation will have
been greater to achieve the observed
post-accident impact scar.
Why bother about this?
It is the cutting edge of everyone’s
knowledge.
If we consider impact damage, we can
see the effect on the vehicle structure,
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