1. 18
Casting an innovative
approach to charger reliability
By Guy Pearson, Vice President of Engineering, Delta-Q Technologies Corp.
A
A facilities man
fac
faci
ac
nager walks out to the warehouse, hops on an electric
lift tru or uti
ft truc
uck
ility vehicle, steps on the accelerator and the vehicle
doe t move. He finds the battery is dead. Why? Did the lift truck
doesn’t m
get plugg in? Did an AC breaker trip? Are the batteries at the end
plugge
p ged ?
of life? Is t re an interlock problem? Is there a problem with the
life s ther
lif
charge itse
er itsel
elf? Regardless of the cause, the vehicle is not available to the customer, resulting in lost productivity and an expensive
cust
cus
ust
service call to the vehicle OEM. Charging related issues can negatively affect end customer satisfaction and cause original equipment
manufacturers (OEMs) a lot of grief.
In a break with traditional practice in this sector, we developed a
fully sealed, rigid die cast aluminum construction, which allows for
multiple features to be cast-in. This approach of integrating multiple
features into key components has been used extensively throughout the product design concept, significantly reducing the secondary
parts count and assembly time. This is formally known as Design
For Manufacture (DFM). By using a die cast housing which also
doubles as the heat sink, we were able to provide the charger with
distinctive angled fins that allow equally effective cooling when
mounted in any orientation.
Delta-Q views improved charger reliability as a significant opportunity in all the markets we serve, including golf, utility vehicles,
aerial work platforms, and lift trucks. End user customers expect
their equipment to work for the expected service life, and often a
“second life” when the equipment is resold. Battery chargers are
also one of the hardest working components in an electric drive system. Regardless of vehicle usage, a charger will be used for up
to 8 to 10 hours daily. Given the transition away from traditional
low frequency ferroresonant chargers to smaller, more efficient high
frequency chargers, more OEMs are moving chargers on-board the
vehicle. With the transition to the more aggressive on-board environment, battery charger reliability becomes a principal concern.
What does reliability mean to an end user? Simply put, the charger is
plugged in and it just works. When the charger is mounted on-board,
long-lasting reliability is a unique challenge to engineer. Reliability
has to be a major goal at each point in the design and manufacturing
process of the charger. Reliability cannot be retrofitted.
In 2010, we began the process of building a new industrial battery
charger from the ground up. We had learned many lessons about
charger durability in the nine years between the release of our QuiQ
industrial battery charger and the start of development on a new 650
watt industrial battery charger, now called the IC650.
Designing for reliability
An on-board environment subjects the battery charger to an unfavorable mix of conditions. Vibration, water, heat and chemicals,
including the corrosive mix of salt and sulfur, are a continuous
challenge to on-board electronics. Vibration is particular challenge
because every environment—in golf, aerial work platforms, utility
vehicles, etc.—subjects the charger to a different vibration profile
varying from high frequency low-g to significant mechanical shock.
To effectively protect on-board electronics from dust and liquids,
the enclosure, including all connections, must be fully sealed. Sealing presents its own challenges, not the least the ability for the charger to reject heat effectively.
IC650: Customer feedback pointed to an aluminum
die cast enclosure that would allow a unique
diagonal fin design for the IC650’s heat sink
Delta-Q’s engineers assembled all of the electronics onto one printed circuit board with maximum use of machine-placed components.
This approach minimizes inter-connections and manual processes,
which are a significant cause of reliability issues. The interfaces
between the enclosure and the board deliver features such as heat
transfer, vibration protection, electrical isolation and EMC compliance without the need for additional components, resulting in a robust and cost effective design.
The selected concept design was analyzed using state of the art
techniques such as finite element analysis for mechanical durability,
computational fluid dynamics for heat rejection and worst case analysis for circuit design. This detailed analysis coupled with stringent
continued on page 20

2. 20
continued from page 18...Charger Reliability
de-rating for all components helps guarantee that the final design
will meet requirements optimally the first time through.
Manufacturing for reliability
As was previously mentioned, the IC650 was designed using DFM
principles. As a result, the charger can be manufactured and assembled in less than a quarter of the time of previous generation products. This delivers obvious cost of manufacturing benefits. DFM
also contributes to reliability, as the more complex a product is to
assemble, the greater chance of getting it wrong.
Automated equipment assists the assembly process by taking out the
variation that humans inevitably contribute. Advances in manufacturing techniques allow traceability of every component and records
each of the many production test steps applied. This level of data is
recorded against the product’s serial number, so the complete history of manufacture can be accessed at any time.
Experience tells us that the end user needs quick action on any service call. This level of traceability is important to determining the
origin of a problem and getting the vehicle or equipment back into
service as soon as possible.
Professionals in the automotive and industrial sectors have analyzed
every significant failure mechanism that has been observed in power
electronics products in the range of environments and applications
in which sealed chargers are used. These failure mechanisms include effects such as high temperature diffusion, thermal shock cycling damage, vibration fatigue, altitude, and corrosive chemicals.
Batches of test units are subjected to more severe stress levels than
would ever be seen in the field.
IC650 chargers were subjected to water ingress tests and corrosive
chemicals. It was shaken, shocked, dropped from six feet multiple
times in every orientation, thermally cycled hundreds of times and
subjected to intense ultraviolet light for hundreds of hours. After all
of this, chargers still worked every time.
We used a Highly Accelerated Lifetime Testing (HALT) chamber to
deliberately break chargers and understand their weakest points. Not
content with formal validation tests, we installed a group of units in
a real-world application to accumulate months more of usage data.
Improvements were made to the design of the IC650 as a result,
especially in areas related to on-board installation. As a result, the
IC650 is uniquely prepared to face the rigors of a long, harsh industrial life, especially in on-board installations.
New approaches to durability
Testing for reliability
Brian Ceresney with HALT chamber: Highly Accelerated Lifetime Testing (HALT) is a critical component
of developing durable chargers.
Automotive development methods informed the IC650 charger’s
durability testing. These processes are tailored to deliver a lifetime’s
worth of cumulative damage from a “1 in 500 severe user” in a relatively short period of time.
The battery charging approach we have observed as the most convenient and beneficial to customers has the charger mounted on-board
and easily plugged into the nearest electrical outlet. Since the onboard installation of the charger exposes it to more wear and tear,
rigorous “automotive thinking” must be applied at every step of the
design and manufacture of chargers to provide the utmost in durability. There is a mindset rooted in the use of traditional off-board
chargers that connects reliability with reparability, but this isn’t a
good strategy for on-board chargers. Having a charger that does
not need repair and works every time is a superior approach. This
goal is realistic and within our reach, but requires great discipline
throughout design, manufacturing and testing product development
processes.
About the Author: Guy Pearson has over 20 years of automotive industry experience, including vehicle, system, component and process
design and development. At Delta-Q, Guy’s responsibilities include
engineering, program management and quality. Previously, Guy
was VP, Engineering at Azure
Dynamics, a developer of hybrid
powertrains. Guy has also held
senior positions at MSX International, UK Midlands Engineering Centre, Johnson Controls
Inc. and Rover Car Company,
where he began his engineering
career in the Advanced Powertrain Group.
.....