We gathered at Navy Pier on a beautiful fall day, ready to enhance our technical knowledge, connect with other local NI users, and introduce visitors to DMC. Our tilt table demo proved to be a popular draw and DMC's team had a great time showing it off at the booth. 

As always, meeting and developing relationships with National Instruments and peer integrators was a highlight of the day. We even raffled off a Fitbit Charge HR. Congratulations to our winner, Sonny Mitric of Omron!

There were plenty of insightful technical sessions to choose from throughout the day. The Advanced DAQmx Property Modes presentation offered a deep technical dive into a useful topic that's applicable in many different applications. We also attended sessions on LabVIEW for Embedded Systems and gained hands-on experience using CRIO for Real-Time and FPGA application. Another course demonstrated good electrical engineering wiring practices, shielding, and noise reduction.

DMC is an active participant in the Chicagoland LabVIEW User Group, so we were excited to see the Midwest User Group at NIDays. We stopped by the Midwest User Group booth and met up with users from across the region at a lunch meeting. 

We wrapped up the event with a fun exercise as part of the closing keynote session. Building a LEGO duck as a demonstration of stem execution was an enjoyable way to end a valuable day of learning and networking. 

Don't miss DMC at NIDays Boston 2015 on November 17!

Learn more about DMC's Test & Measurement Automation services.

The post Duck, Duck, DAQmx: NIDays Chicago 2015 Recap appeared first on DMC, Inc..

One of the bigger test and validation challenges out there involves testing the battery management system (BMS). (Background of PHEV automotive battery packs and battery management systems)

Modern BMS systems for PHEV applications are typically distributed electronic systems. In a standard distributed topology, routing of sense wires to individual cells is minimized by breaking the BMS functions up into at least 2 categories. The monitoring of the temperature and voltage of individual cells is done by a BMS ‘sub-module’ or ‘slave’ circuit board, which is mounted directly on each battery module stack. Higher level functions such as computing state of charge, activating contactors, etc. along with aggregating the data from the sub modules and communicating with the ECU are done by the BMS ‘main module’ or ‘master’. Subsets of these higher level functions could also be provided by additional auxiliary modules. The sub-modules, main module, and any auxiliary modules communicate together on an internal data bus such as CAN (controller area network).

During BMS Testing and Development, engineers need a way to reliably test the BMS under real-world conditions to complete their verification and validation test plans. Testing such as Hardware-in-the-Loop (HiL) is often performed at this stage. HiL testing involves simulating physical inputs and external digital connections to the pack while monitoring its outputs and behavior relative to design requirements.

It is not easy to accurately simulate all of the real-world conditions a BMS will be subjected to. But what does it cost you to skip testing over every condition? In the end, simulating nearly every combination of cell voltages, temperatures, and currents you expect your BMS to encounter is really the only way to verify that your BMS reacts as you intended in order to keep your pack safe and reliable.

Once you decide that testing your BMS in this way is a necessity, you need to determine a strategy to complete that testing. It is tempting here to over focus on hardware cost minimization. While up-front cost certainly is always a factor, it must be weighed against the hidden costs of ineffective or incomplete testing. In the most extreme cases, the latter potentially involves serious safety and reliability failures. As an example, let’s explore three different approaches to balancing tooling costs with an accurate test strategy.

BMS Testing Strategy One:

Let’s start by trying to use standard analog outputs channels from our DAQ system to simulate our (let’s say 64) cells. We could try this to save some up-front costs, or maybe that’s our only option, for example, if we are using an existing d-SPACE HiL platform. Since the voltage outputs are not isolated from ground, we cannot stack too many of them in series, or else our common mode voltage will exceed the isolation rating of our AO channels. AO channels on most DAQ cards don’t source or sink much current, but let’s ignore that for now. We’ll still be able to measure the voltage response of each input to our BMS, it will just be done 8 cells at a time, as shown in the figure below.

BMS Testing Strategy Two:

If we have some extra budget left, maybe we can use some good power supplies, or even source measure unit (SMU) channels, to simulate our cell voltages. SMUs are basically very accurate 4-quadrant power supplies, so we will have many options for running them in CC or CV mode, setting limits, making measurements, etc. Either way our hardware will be able to sink and source all the current our BMS expects it to, as opposed to the AO DAQ channels above. However, since SMUs on the market today do not have high isolation options, we are still forced to test only 8 cells at a time.

BMS Testing Strategy Three:

Here we decide that we need to test all cells at once, exactly as things would happen inside a real battery pack. Our only option is to use high-isolation, programmable voltage output channels which both source and sink adequate current. Now we can stack all the simulated voltage channels together in series. We can test everything at once, and we simulate the complete BMS environment, not just the environment of one of the slave modules, as shown below.

BMS Testing Strategy Comparisons:

In Cases 1 and 2 above, clearly we spend more time testing our entire BMS with our piecewise, round-robin approach, than in the direct approach of Case 3. But that is only the clearly obvious difference.

Using strategy one, we don’t spend much money on hardware. However, we lose the ability to accurately emulate a battery cell since our current source/sink range is not very high. In this case, we will may never know if one cell monitoring line in our BMS is drawing more or less current than specified. This could lead to a battery cell which is always getting discharged or charge more than its neighbors, leading to constant cell imbalance conditions.

Using strategy two, we will spend a bit more on hardware to provide accurate battery emulation on the current supply/sink side. However, what we are still missing is the application of high relative voltages to all stack sense lines at the same time. What this means is you will never know the true performance of your BMS under real world conditions. Sure you’ve characterized everything, but not at the same time.

Assume there is some strange leakage path between cell lines 7 and 24 within the cabling and routing of all these sense points within your real BMS setup. How will you catch that if the two lines are never tested at the same time with the real potentials available with your full battery stack?

As anyone in the industry knows, the diagrams shown above are very simplified depictions of the real routing inside a pack between pieces of a modular BMS. So how many more situations like this can you think of? Better yet, how many would you never think of, until you catch them during your testing?

Conclusions:

Strategy three is clearly the only way to accurately simulate inputs to your entire BMS system. You need to use high-isolation, programmable voltage output channels and stack all the simulated voltage channels together in series. If you’re not going to do that, at least you have to understand and accept the trade-offs being made.

Learn more about DMC’s expertise in battery pack and BMS test systems.

The post Battery Management System (BMS) Testing Strategies appeared first on DMC, Inc..

Check out the Battery Management System Test Stand Case Study for a full description of the system.

Here are a few high res photos of the completed system:

SO WHY IS IT SO TALL?

The first question other engineers at DMC asked as the test stand was being assembled was “Why is it so tall?” Soon enough, the DMC office had nicknamed the test stand “The Monolith” as it towered silently above all other equipment in our lab. Then we delivered the test stand to the customer, and the first question people asked as they saw it was a familiar “Why is it so tall?”

The test stand structure was, in fact, chosen with forethought and deliberate planning based on an understanding of the customer’s requirements, testing practices, and future plans.

The threefold answer to the question is: Expandability, Modularity, and Mobility

Expandability

Only about two thirds of the total vertical space in the test stand case was actually used to house the hardware needed to meet the original test stand specifications and requirements. The remaining space was reserved for future use to make the test stand easily expandable and upgradable to meet any yet-to-be-defined features that may be desired down the road. By working side by side with the customer on past projects, DMC has acquired a good understanding of how the customer’s testing plans and requirements develop and mature over time. In this project, we knew there was a VERY good chance that ever changing test plans would necessitate new features and new hardware devices in the future. As it turns out, we’ve already had requests to add some new instruments to the tester, so planning ahead with expansion capacity has already paid off in this area!

Modularity

The second driving factor in choosing the vertical rack mount structure for the test stand is that it allows us to organize subsystems of the test stand in modular “boxes” that can be easily removed, added, or even vertically rearranged within the test stand. With this setup, if modifications, repairs, or upgrades are required for a particular subsystem of the test stand, that module can be removed (allowing easy access while working on it) and then reinstalled, without requiring any major disassembly and preventing disruption to all other test stand systems. This modular architecture is made possible by the standardized rack mount frame that was utilized and makes for a system with greater overall flexibility and maintainability.

Mobility

The battery business is a busy one these days, and at the customer’s facility, laboratory floor space is in high demand for the various development, testing, and production activities that are all occurring in tandem. As soon as the system went into service, the advantages of having a single, consolidated, and compact test stand with a small horizontal footprint became immediately clear. It was able to be maneuvered conveniently to needed locations so it could churn away at automated test sequences without interfering with other traffic and activities.

In Conclusion

So I guess the moral of this story is that developing a successful system is about more than meeting a customers requirements and specifications line item by line item and walking away. At DMC, it involves combining experience (gained from a myriad of past projects) and a full understanding how a particular customer operates (gained by establishing a close working relationship with them). These two elements let DMC go beyond providing a solution that gives the customer what they need today, to make the latent and unmet needs of tomorrow easy to fulfill.

The post BMS Test Stand Towers Over the Competition appeared first on DMC, Inc..

Before we shipped this tester, we wanted to demonstrate using the system to test a BMS in manual mode, to illustrate the basic capabilities of the battery cell simulators, software, and other electronics. However, the automotive BMS boards we have designed this system to test are, of course, proprietary to the PHEV battery pack vendor. In place of these 100 cell BMS devices, we have substituted an off the shelf BMS from Texas Instruments (TI).

For several older battery projects, DMC had been testing TI BQ20z90 based fuel gauge chips for use in laptop and portable electronic device battery packs. So we have a pretty good understanding of how they work. More importantly, we have a BQ20z90 evaluation board lying around with the evaluation software.

With these tools, the BMS test stand, a video camera, and some very limited spare time, we put together a two-part demo.

Part One:

Part Two:

The post Video Demonstration of BMS Test Stand Basic Capabilities appeared first on DMC, Inc..

• Hydrogen Fuel Cell Customizable Test Platform
• Smart Battery Pack Manufacturing Test
• Hybrid Electric Vehicle Battery Test System
• Battery Pack Monitor System for Environmental Testing

Lithium battery packs and hydrogen fuel cell stacks are two of many promising emerging technologies for future energy needs. They also share another important design characteristic: both provide high voltages by stacking together multiple cells. While this method of stacking does provide the required voltage output for applications such as HEV automobiles, it also requires precise monitoring and control to ensure that each of the individual cells remains within a standard operating range. Battery packs accomplish this control using a Battery Management System (BMS).

DMC has partnered with Pickering Interfaces to design a system which allows the simulation of a battery pack down to the individual battery cells and helps vendors to develop, test, and validate these complicated control systems with greater efficiency. While Fuel Cell Management systems are more complex and require additional control (i.e. fuel, oxidant, and coolant flows, along with thermal regulation), their development still requires the simulation of the fuel cell stack and its numerous individual current producing cells. To read more about this new system and learn about the benefits it provides to developers of management systems check out Battery Management System (BMS) Validation Test Stand.

The post Use of BMS Validation Test Stand for Fuel Cell Management System Testing appeared first on DMC, Inc..

The article discusses new test and validation challenges associated with electric vehicles (EVs). As the popularity of electric vehicles in the automotive scene increases, so does the importance of testing a Battery Management System under all battery stack conditions. The article details the collaboration of DMC and Pickering Interfaces to help provide a solution to BMS testing based on PXI modules that emulate the battery systems.

The result of this direct vendor collaboration between DMC and Pickering is their newly released 41-752-001: 6-channel PXI battery cell simulator module. In addition to working with Pickering to develop the new BMS DMC is also the first to use the new product, having employed it in multiple test set-ups. The project scope is a natural fit for Evaluation Engineering, a magazine for engineers and engineering managers responsible for test and total product quality in electronics.

With our extensive experience in battery testing, DMC has also recently published a white paper compiling several challenges to, and lessons for, EV battery pack testing. A recent case study detailing the development of DMC’s BMS Validation Test Stand is also available.

For more information regarding this product, please do not hesitate to contact us.

The post Battery Management System (BMS) Testing Article Featured on Evaluation Engineering appeared first on DMC, Inc..

“Electric Vehicle Battery Pack Testing in a Manufacturing Environment”

If you are interested in the automotive battery packs used in electric vehicles (EVs), hybrid electric vehicles (HEVs), and plugin hybrid electric vehicles (PHEVs) and how they are tested, this article should contain some pretty useful information.

If you are new to the EV battery world, the article contains a good starting place to begin your learning process. If you’re already in the EV field, it should serve as a good reference and hopefully provide some pointers on best practices for implementing a testing strategy.

If you are interested in our Battery Testing Platform here are some case studies to browse.

Abstract:

Electric vehicles are clearly becoming a growing part of the automotive scene. They promise low or no emissions, conceivably low cost of fuel from the power grid, yet they will continue to deliver us safely from here to there. However, electric vehicle design and manufacturing is a clearly a paradigm shift for the Auto Industry – new drive systems, technologies… and test plans.

Electric vehicles are bringing new test and validation challenges to the automotive industry as the electronic and software content of the vehicles grow. In this white paper, we will discuss the basics of electric vehicle battery pack designs and some of the tests that should be performed on them in a manufacturing environment. We’ll also show you how the DMC Battery Testing Platform can help solve these complex testing problems.

The post New White Paper: Electric Vehicle Battery Pack Testing appeared first on DMC, Inc..

Check out these Case Study entries to read more detail!

Sharepoint Timesheet Entry Portal

Battery Management System (BMS) Validation Test Stand

Battery Pack Monitor System for Environmental Testing

The post Check out our new Case Studies! appeared first on DMC, Inc..

It’s not every day you get to dream up your own test and measurement instruments, but I guess that is what we’ve just done. The result of this direct vendor collaboration between DMC and Pickering is their newly released 41-752-001: 6-channel PXI battery cell simulator module.

Several of the Pickering battery simulator cards can be chained together in a single PXI or LXI chassis to simulate a large stack of batteries. Such large battery stacks are commonly used in packs designed for PHEV (plug-in hybrid electric vehicle) and HEV (hybrid electric vehicle) automotive applications.

Having a stack of batteries you can control is useful for verification, validation, and HiL (Hardware in the Loop) testing of BMS (Battery Management System) and battery control modules. Ensuring that a BMS design responds as required, under all battery stack conditions, even extreme and worst-case scenarios, is something you want to test before your battery pack gets into the field. And the only way to really do that at the hardware level is to have a battery stack simulator you can completely control and trust.

For more information about using this product do not hesitate to contact us.

Author Note 2/12/2010: Check out our new white paper on EV Battery Pack Testing

Further reading and links:

The DMC Case Study for our BMS testing solution here.

All DMC Battery Related Case Studies.

More technical information about BMS HiL testing here.

Learn more about DMC’s battery pack and BMS test stand expertise.

The post New PXI Battery Simulator for PHEV Automotive Applications appeared first on DMC, Inc..

“This seventh annual event will feature more than 30 presentations on portable, stationary and automotive battery technology, as well as battery manufacturing, materials and research & development. Topics will include new battery designs, emerging technologies, battery materials, power management, charging and testing systems, battery health, as well as the latest market trends affecting the industry.”

DMC is proud to continue it’s active role in the rapidly emerging world of alternative energy technologies. We’ve been very successful in providing world-class test systems for research, development, and manufacturing, and have been increasing our role in the market since starting in it nearly 10 years ago.

Examples of our work in this field can be found in the following links:

Hybrid Electric Vehicle Battery Test System

Smart Battery Pack Manufacturing Test

The post Battery Power 2009 appeared first on DMC, Inc..