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nager walks out to the warehouse, hops on an electricility vehicle, steps on the accelerator and the vehicle He finds the battery is dead. Why? Did the lift truck ? Did an AC breaker trip? Are the batteries at the end re an interlock problem? Is there a problem with the

Regardless of the cause, the vehicle is not avail-able to the customer, resulting in lost productivity and an expensiveservice call to the vehicle OEM. Charging related issues can nega-tively affect end customer satisfaction and cause original equipment manufacturers (OEMs) a lot of grief.

Delta-Q views improved charger reliability as a significant oppor-tunity 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 arealso one of the hardest working components in an electric drive sys-tem. Regardless of vehicle usage, a charger will be used for upto 8 to 10 hours daily. Given the transition away from traditionallow frequency ferroresonant chargers to smaller, more efficient highfrequency chargers, more OEMs are moving chargers on-board thevehicle. With the transition to the more aggressive on-board envi-ronment, battery charger reliability becomes a principal concern.

What does reliability mean to an end user? Simply put, the charger isplugged in and it just works. When the charger is mounted on-board, long-lasting reliability is a unique challenge to engineer. Reliabilityhas to be a major goal at each point in the design and manufacturingprocess 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 unfa-vorable 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 profilevarying 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. Seal-ing presents its own challenges, not the least the ability for the char-ger to reject heat effectively.

Casting an innovative approach to charger reliability

By Guy Pearson, Vice President of Engineering, Delta-Q Technologies Corp.

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 through-out the product design concept, significantly reducing the secondary parts count and assembly time. This is formally known as DesignFor Manufacture (DFM). By using a die cast housing which alsodoubles as the heat sink, we were able to provide the charger withdistinctive angled fins that allow equally effective cooling when mounted in any orientation.

Delta-Q’s engineers assembled all of the electronics onto one print-ed 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 compli-ance without the need for additional components, resulting in a ro-bust 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 anal-ysis for circuit design. This detailed analysis coupled with stringent

IC650: Customer feedback pointed to an aluminum die cast enclosure that would allow a unique diagonal fin design for the IC650’s heat sink

continued on page 20

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de-rating for all components helps guarantee that the final designwill meet requirements optimally the first time through.

Manufacturing for reliability

As was previously mentioned, the IC650 was designed using DFMprinciples. As a result, the charger can be manufactured and assem-bled in less than a quarter of the time of previous generation prod-ucts. This delivers obvious cost of manufacturing benefits. DFMalso contributes to reliability, as the more complex a product is toassemble, the greater chance of getting it wrong.

Automated equipment assists the assembly process by taking out the variation that humans inevitably contribute. Advances in manufac-turing techniques allow traceability of every component and records each of the many production test steps applied. This level of data isrecorded against the product’s serial number, so the complete his-tory of manufacture can be accessed at any time.

Experience tells us that the end user needs quick action on any ser-vice 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.

Testing for reliability

Automotive development methods informed the IC650 charger’sdurability testing. These processes are tailored to deliver a lifetime’s worth of cumulative damage from a “1 in 500 severe user” in a rela-tively short period of time.

About the Author: Guy Pearson has over 20 years of automotive in-dustry experience, including vehicle, system, component and process design and development. At Delta-Q, Guy’s responsibilities includeengineering, program management and quality. Previously, Guywas VP, Engineering at Azure Dynamics, a developer of hybrid powertrains. Guy has also held senior positions at MSX Interna-tional, UK Midlands Engineer-ing Centre, Johnson ControlsInc. and Rover Car Company,where he began his engineering career in the Advanced Power-train Group.

continued from page 18...Charger Reliability Professionals in the automotive and industrial sectors have analyzedevery 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 in-clude effects such as high temperature diffusion, thermal shock cy-cling 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 corrosivechemicals. It was shaken, shocked, dropped from six feet multipletimes 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 todeliberately break chargers and understand their weakest points. Not content with formal validation tests, we installed a group of units ina 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, theIC650 is uniquely prepared to face the rigors of a long, harsh indus-trial life, especially in on-board installations.

New approaches to durability

The battery charging approach we have observed as the most conve-nient and beneficial to customers has the charger mounted on-board and easily plugged into the nearest electrical outlet. Since the on-board 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 dura-bility. 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 doesnot 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.

Brian Ceresney with HALT chamber: Highly Acceler-ated Lifetime Testing (HALT) is a critical component

of developing durable chargers.