〉〉New ProductsHigh Voltage Junction Boxes for Isuzu ELF EV

1.

INTRODUCTION

2.

The global warming caused by increasing emissions ofgreenhouse gases such as CO2 has given rise to various
abnormal weather to be a major environmental problem
all over the world. The Japanese government declared toaim at the “Carbon Neutrality” by 2050 to solve these
problems and has settled on “Green Growth Strategy
Through Achieving Carbon Neutrality in 2050”. Targets
such that 100% of new car sales should be Electric
Vehicles (EV) by the middle of the 2030s were presented tothe automotive industry and the spread of Electric Vehicles
such as Battery Electric Vehicles (BEV) and Hydrogen
Fuel-Cell Vehicles (HFCEV) has been accelerated.
Considering the BEV, a high voltage junction box isrequired to distribute the power from batteries to various
high voltage units and equipment. The high voltage junction box requires such technologies as the heat radiation
design against an increased electric power flow, the insulation design against a higher voltage and the metal
housing design to protect from an electric shock at a collision, none of which are required for a low voltage junction box used in a gasoline fueled vehicle.
Further, as our developed high voltage junction box is a
product mounted on a frame under a cabin of a commercial vehicle (Figure 1), higher corrosion resistance andsuperior vibration resistance are required in comparison
to that on a passenger car.
We have developed and successfully launched our highvoltage junction box mounted on the “ELF EV”, which
was the first mass-produced battery truck of Isuzu
Motors Limited, by merging and advancing our design
technology and production technology which have beendeveloped on our high voltage junction boxes already inproduction for passenger vehicles and our present low
voltage junction boxes and wire harnesses.

AN OUTLINE AND STRUCTURE OF
THE PRODUCTAn EV version was newly introduced in the “Isuzu ELF”
series, which have been just brought out to be fully newmodel series for the first time since the last 17 years. We
developed the conversion box (Figure 2) for “ELF EV”
which was sold for domestic use and have started todeliver the mass-produced product since July 2023.
Further, we have developed the high voltage junction box(Figure 3) for the same vehicle (called in U.S. as N seriesEV) which will be sold in North America and planned tostart the mass-production in the first half of 2024.

Figure 2

Figure 3

High voltage junction box(mounted under the cabin)

Conversion box(This photo was offered by Isuzu Motors Limited.)

Figure 11)

The position where the boxes are mounted .

Conversion box.

High voltage junction box (9-pack specification).

Our high voltage junction box developed this time hassuch functions as to distribute power from battery packs
to inverters, motors, heaters, A/C compressors and otherequipment appropriately when running and on the other
hand, to distribute power from the power charger to theFurukawa Electric Review, No. 55 2024

67

High Voltage Junction Boxes for Isuzu ELF EV

battery packs appropriately when charging. High current
circuits are constructed with busbars punched out from acopper strip by presswork, which have a larger surface
area and a larger cross-section in comparison with wires,and those circuits for low to medium current are constructed with either busbars or wires in combination torealize the optimum circuit arrangement. The busbar issecured in plastic parts to secure the required insulation
distance and satisfy the required withstand voltage performance.
The high voltage junction box includes high voltage
fuses to protect onboard equipment from an overcurrent,
current sensors to detect battery state and the Master
Battery Management System (MBMS). Further, an interlock circuit is equipped for protection from an electric
shock from a high voltage. Signal circuits and interlock
circuits connected to the MBMS are constructed with low
voltage wire harnesses in which wire routes, positioning
methods and circuit protection are appropriately
designed using our present wire harness design technology.
According to the number of onboard battery packs (3,5, 7 up to 9 packs according to the driving mileage of avehicle), four models of the high voltage junction box
were deployed in our lineup to respond with flexibility tovarious needs from our customer.

3.

Busbars

MBMS

Temperature (℃)
60

Figure 4

65

70

75

80

85

Results of thermal analysis.
Plastic components

Relay

FEATURES OF THE HIGH VOLTAGE
JUNCTION BOX

Our high voltage junction box has the three featuresshown below including its production method.
1) Established the space-saving design inconsideration with the enlarged amount of heatgenerated by higher current
Our high voltage junction box, which could be connected with 3 packs of battery at maximum for domestic use
and 9 packs at maximum for the North American use has
been capable for the increased current since the “ELFEV” was launched, which was then sold for domestic use.
Considering the increased heat generation caused by theincreased current, a high heat-resistant performance issecured by controlling the temperature of mounted components to be no higher than their heat withstand temperature through optimizing the structure of busbars (crosssection and circuit route) and the layout of other innercomponents based on the visualized heat generation
state in our heat simulation (Figure 4).
We have realized a high space factor in our high voltage
junction box through placing plastic components
between a low heat-resistant MBMS against busbars andrelays from which heat was generated to control the heattransmission from the heat-generating source (Figure 5).
Furthermore, wires were also applied to the inner circuitin combination with the busbars for the optimum circuit
arrangement based on our technology developed in ourwire harness development. Adopting those technologies

90MBMSBusbars
Figure 5

Layout of internal components.

mentioned above, we have realized a product thatenables to connect to up to a maximum of 9 battery
packs even though it was maintaining a product size
same as that for the vehicle of domestic use (3 packs atmaximum).
The space factor which is the ratio of the volume ofcomponents installed in the box against the volume ofinternal space of the metal housing has been improvedby 5 times in comparison with that of our present product. (Figure 6)

Furukawa Electric Review, No. 55 2024

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High Voltage Junction Boxes for Isuzu ELF EV

10090

Space factor / %

80
7060

Volume ofinternal space

50

Volume ofcomponents
in the box

4030
2026.4

100Figure 6

Figure 8

5.2Presentproduct2)

Transportation of molten metal .

Newly developedproductComparison of the space factor with our present
product.

2) The high voltage junction boxes with different
number of battery packs were deployed in ourproduct lineup
We have set up 4 models of the high voltage junction
boxes in our lineup to satisfy various set-up of battery
packs according to the cruising range required by a user.
We have not only satisfied a flexibility to our customer’s
requirements mentioned above but also reduced cost by
applying common components and the metal housingscasted in a common die but partly machined for minor
variations (Figure 7).

4.

CONCLUSION

We have realized such a high voltage junction box capable handling 9 pack circuit specifications even in theequivalent space of the one handling packs for vehicles
for domestic use and the space factor of components
installed in the housing has been improved by 5 times incomparison with that of our present product. It is forecasted that from now on, still higher voltage and larger
current will be increasingly required to be handled in thejunction box and that the volume of internal components
will increase further. We will work on the development of awide range of automotive products 3) using the technology
built up in this development to contribute to accelerate
the spread of BEV and accomplish the target of theCarbon Neutrality in 2050.

REFERENCES
9 packs
Figure 77 packs

5 packs

3 packs

Variation of the metal housing.

3) Review our production process to reduce CO2
significantly
We have adopted such a production method of aluminum die-cast to produce the metal housing of the product as we directly bring melting aluminum material in froma material manufacturer (a smelter) and cast the productinstead of applying usual aluminum ingots (Figure 8). With
this process which has no melting process of ingot, weare saving CO2 by approximately 40% in comparison withthe emission generated in the case of re-melting theingot, and hence reduce the emission of CO2 during theproduction process.

1) Photo of the position where the boxes are mounted (ISUZU Nseries NRR EV truck)		 Isuzu Commercial Truck of America, Inc HP > N-SERIES EV		 (Referred on Jan. 24, 2024)		https://www.isuzucv.com/en/nseries/nseries_ev2) Photo of transportation of molten metal		 Daiki Aluminum Industry Co., Ltd. HP > CSR > Commitment tothe environment > CO2 reduction (Referred on Jan. 24, 2024)		https://daikialuminium.com/csr/environment/co2/3) Furukawa AS HP > Products (Referred on Feb. 14, 2024)		https://www.furukawaas.co.jp/english/products/

For more information, please contact:
Sales Planning & Marketing Department,
Sales Management Department,
Automotive Products Division
Contact form:
https://inquiry-fec-form.spiral-site.com/enjidosya

Furukawa Electric Review, No. 55 202469