Hybrid high voltage battery pack testing and analysis

Jan. 1, 2020
  There is a new revenue stream in pursuing high voltage (HV) hybrid electric vehicle (HEV) battery packs diagnostics or service.

Automotive aftermarket owners and technicians should be listening for a knock on their business door.  It’s the sound of a new revenue stream opportunity that may be virtually untapped by many automotive businesses that are not actively pursuing high voltage (HV) hybrid electric vehicle (HEV) battery packs diagnostics or service or, for those businesses that have not entered this market and have interest in pursuing new revenue opportunities. 

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The thesis of this article will be to provide information in how to use additional HV battery pack testing processes and procedures that can be utilized in offering additional product enhancements to your customer.  This results in a superior (known quantity) product for the customer and an additional revenue stream for your business.

The Anatomy of an HV HEV Battery Opportunity
The HEV entry into the automotive market in model year 2000 was the birth of a new opportunity.  Any battery pack unit from a new or used vehicle provides an opportunity for an automotive business to analyze/diagnose, service, recondition, or rebuild the unit.  With warranties expiring on thousands of hybrid vehicles each year, and 57 hybrid vehicle models entering the market as of the 2013 model year, battery packs will offer a tremendous opportunity for the aftermarket to begin carving out a new business market – and initiate an additional profit center.  An aftermarket service business also has opportunities to purchase used (core) battery packs from the secondary (salvage) market and rebuilding these packs for use in customer vehicles at a minimal capital investment. 

However, just because an aftermarket business may desire to enter the battery pack service market or, have access to a used part core doesn’t mean that they are fully capitalizing on its value.  Value to a customer, when applied to a HV hybrid battery pack system, means that the battery pack: 1) is clean, 2) modules have been analyzed and tested (test data has been acquired and documented) and can perform to a stated industry accepted specification, 3) is safe and has no HV isolation fault condition that could (electrically) harm the installer customer or vehicle operator when the battery pack is being tested or installed 4) cause a loss of propulsion during the drive cycle of the vehicle, and 5) warranty will provide power and energy levels necessary for adequate vehicle performance and fuel economy during the stated warranty period (e.g., 6 or 12 months) and beyond for a high cost component.

Value to the business owner would encompass the elimination of all the battery pack module performance unknowns and that the customer has received a fully functioning battery pack module system.  In my 25 years in engineering, testing and servicing hybrid/electric/fuel cell vehicle propulsion systems I have never seen a time where an aftermarket service and parts business could so easily reinvent their business model by pursuing opportunities in these new technologies – HV Nickel Metal Hydride (NiMH) and Lithium Ion hybrid battery systems in particular.

Why Should You Purchase a Rebuilt Battery Pack and Lose All of the Profitability?
Let’s list some of the reasons why an automotive repair business may be capitalizing on a high profit business opportunity. First, purchasing a new hybrid battery pack from the OEM dealer can be extremely expensive as a repair.  

Therefore, many aftermarket repair businesses won’t even entertain the idea of battery pack service for their customers and furthermore, because most businesses will not engage in battery pack service, they will not advertise or market that they can repair hybrid battery pack systems – therefore, a new profit stream cannot be realized (for vehicles in or out of warranty).  Second, there are aftermarket hybrid battery pack rebuilding companies and some vehicle service businesses that are rebuilding hybrid battery packs commercially.  The cost of these battery packs is less expensive than an OEM dealer unit but, the expense remains high.  However, there is an ancillary issue when considering purchasing a battery pack from an independent (aftermarket) rebuilder.  Most of these rebuilders are “self-taught” rebuilders and lack the requisite professional training and experience necessary to provide a quality battery pack recondition or rebuild, and have not developed essential testing and rebuilding processes or techniques to ensure a quality product. 

Some of the most popular aftermarket hybrid battery commercial rebuilders (that you may have already purchased product) are the very same rebuilders that are self-taught and lack the requisite skills previously mentioned.  In summary, you really won’t know what type of product you’re receiving when acquiring it from an aftermarket rebuilder – even if they are well known and very popular in the industry.  Remember, acquiring a battery pack from a well known and popular rebuilder doesn’t guarantee a quality product.  Third, an aftermarket service business may feel that it is cost prohibitive to jump into the battery pack service business because “the tools and equipment necessary to properly analyze and test the battery pack are just too expensive and there is no return on investment.”   This sentiment may be driven from the feeling that “there just isn’t enough profit in hybrid vehicle battery pack repair.”  Well, let’s look at the cost data and you may be surprised at the return on investment.  Based on recent cost data here are some interesting facts (using a 2006 Toyota Prius battery pack as an example) for three possible customer repair scenarios:

Ø  Cost of new unit from OEM dealer:  $2,528.00 (plus $1,350 core charge if no core provided to dealer). Many aftermarket businesses receive a 20% - 25% B2B discount from the dealer.  Final cost approximately $2,000.00

Ø  Cost of rebuilt unit from a commercial rebuilder:  $1875.00 + shipping (plus core charge if no core provided).  Final estimated cost (w/shipping) approximately  $2,100.00.

Ø  Labor time for testing and conditioning customer battery pack or a used donor pack by a service shop:  $320.00.  This assumes that you have the necessary equipment to perform the service.  More on tools and equipment later in the article.

As you can see, there is significant cost in purchasing a new or rebuilt battery pack unit.  However, if you consider testing and conditioning (or repairing) the battery pack as part of your business, the cost decreases significantly!    I’ll bet you’re probably asking yourself “don’t some or all of the battery modules need to be changed during a rebuild”?  The answer is that typically no (NiMH) modules need to be replaced for the battery pack to recover most (if not all) of its original power and energy capacity.  Although there will be some battery packs that will need a module or two to be replaced to acquire the necessary power, energy, and balance.  However, a few used (tested and qualified) battery modules kept on-hand can easily be installed inexpensively to alleviate the problem. 

Therefore, since component replacement is a low probability, why not consider learning the skills yourself (from a qualified and experienced training company) and direct the profits into your business!  The cost of purchasing battery pack testing equipment is much less than you may be assuming, and the return on investment is incredibly high.  As you can view from the previous cost numbers a service shop could easily record a nice profit from moving from a new or rebuilt battery pack to an in-house service for the customer.  Now, let’s take a look at the process of testing hybrid batteries so you can see how easy it really is to perform the testing.

What’s contained in the Battery Pack Testing and Analysis Process?
Whether your business decides to diagnose, recondition, or rebuild a battery pack the process for testing and analyzing the test data of a HV HEV battery pack system will be identical.  Within the confines of this article the following definitions will be used:  1) reconditioned – battery pack modules receive only cycling to achieve adequate power and energy performance, no components are replaced and mild cleaning of bus bars may be necessary, 2) rebuilding – only malfunctioning battery pack components, hardware or modules are replaced (includes bus bars) to achieve adequate power and energy performance, and 3) remanufacturing – specific components are replaced on every battery pack system irrespective of their condition to achieve original (new) power and energy performance.  

During my long career with hybrid and electric vehicle high voltage propulsion systems I have tested hundreds of battery pack systems (Lead Acid, Nickel Metal Hydride, and Lithium Ion technologies).  From 2000 – 2012 hybrids in particular have (to date) been almost exclusively Nickel Metal Hydride (NiMH) module technology.  This is very good news for the aftermarket parts industry.  Since one type of battery chemistry has been dominant, preparing or implementing additional value to the battery pack products and the customer is much simpler and easier.

Another great piece of news is that decades of experience with hybrid NiMH battery packs indicates that most (very high percentage) need only to be conditioned (cycled) to acquire very acceptable power and energy performance, and balance/equalize the module capacities necessary to bring a good value to the customer.  The NiMH battery modules are very resilient and conditioning the modules can increase module capacity to near new Amp•hour (A•hr) levels.  From the perspective of a customer (purchaser) of the reconditioned battery pack this would result in a significantly lower purchase cost.  From the perspective of a business owner marketing a reconditioned battery pack, this would typically mean that disassembly is not required (but may be an option), nor would battery module replacements be necessary to acquire very acceptable levels of power and energy performance – and balance (without all of the additional labor or parts costs). 

Although there is an additional up-front cost to the business owner (in testing and analyzing the battery pack) the benefit is a component with known power and energy performance.  Removing the unknown of how the battery pack will perform is extremely important to the person/business purchasing the battery pack.  Moreover, those individuals or businesses experienced with hybrid battery packs have consistently indicated that most purchasers of used battery packs are most concerned with how the battery modules will perform after installation.  If the battery pack has any performance or diagnostic issues after installation the battery pack must be removed and returned for a replacement unit.   

This is a costly event for both the purchaser and battery pack supplier.  This results in lost revenue, labor time, shipping costs, and an irritated customer.  Therefore, if a business that is marketing reconditioned battery packs can test, analyze, acquire data, and provide a performance report on a battery pack prior to a customer sale the business owner could market the battery pack at a slightly higher cost margin with a warranty ensuring battery pack (known) performance.  This a considerable value point for any customer that is considering the purchase of a used (expensive) battery pack unit and a significant marketing advantage to any business that can provide this value.  In the automotive aftermarket repair business there are small companies forming that are claiming to be hybrid battery rebuilders that an automotive parts rebuilder or remanufacturer must compete with for customers. 

Where Can I Find a Supplier to Help Me?
There are reputable HEV HV battery rebuilders that can provide excellent battery pack rebuilding services.  However, there are far more automotive aftermarket businesses that have entered the hybrid service market within the past five (5) years or longer that are self-taught or have learned from others who themselves were self-taught.  Their testing and analysis techniques, coupled with using sub-standard equipment or just the scan tool are not grounded in good service engineering principles or practices, nor do they possess the requisite experience to supply an optimal reconditioned or rebuilt product.  However, customers of the self-taught suppliers typically don’t know that their supplier is self-taught nor do they know what questions to ask in selecting a qualified reconditioning/rebuilding supplier.  Scary thought isn’t it? 

When selecting a supplier to assist in growing your hybrid HEV battery pack business, whether it is purchasing equipment and associated battery pack training to support an in-house program or selecting a turn-key supplier, there is one key question you should ask them:  Do members of your staff have significant OEM hybrid vehicle manufacturer or OEM hybrid battery pack supplier technical and or engineering experience?  If the answer is yes, ask them for credential documentation (education, professional development, and experience).  A reputable company will be more than happy to supply credentials to you.  If the answer is no then, run from them FAST because, they are likely self-taught which will foster an eventual nightmare for your business.  With organizations that I regularly provide engineering and technical consulting, we are witnessing an explosion of individuals in the automotive aftermarket training arena that claim to be engineers with fraudulent credentials, claim to have significantly more experience than is the actual case, or are completely self-taught but will claim that their methods are “as good as any other methods.”  Some of these individuals are well known nationally and very popular in the automotive aftermarket.  However, popularity coupled with unfounded opinions that are stated as facts, and a big smile won’t feed your business profit model, curb warranty returns, or maintain/increase your industry reputation.  Therefore, I implore you to ask the tough questions before purchasing any aftermarket training, equipment, or rebuilding services!  It will save you time and treasure in unwinding the poisonous effect on your business and customers.

Can’t I Just Use the Scan Tool to Analyze and Diagnose the Battery System?
In short, the answer is no.  The scan tool is merely an interface tool and will only execute algorithms or acquire data that are contained in or provided by the vehicle controller software, and the system is designed only to provide the technician what is “necessary” to maintain the vehicle within regulatory and warranty compliance – and usually a few other “nice” things but nothing more.  Since the vehicle controllers do not contain the capability of executing power or energy tests, the scan tool is of little value for a technician to determine power, energy, conditioning, true balancing or battery pack SOH (State of Health). 

Furthermore, the scan tool (via vehicle controller software) has no capability of determining actual battery pack module (cell) capacities nor provide true cell-to-cell balancing capability in the battery pack module string.  The scan tool does have the capability of performing some cursory diagnostics and provide cell voltages but these tests are merely checks for catastrophic failure conditions and not for true testing, rebuilding purposes or, checking SOH.  Some late-model vehicles containing Lithium Ion technology have limited capability to provide “light cell to cell balancing” but not industry standard power or energy related balancing that is necessary for actual rebuilding or service.  Unfortunately, there are automotive hybrid instructors that are teaching that adequate battery pack analysis can be accomplished by using only the scan tool but the reality is that true analysis, diagnostics, balancing, conditioning, and SOH checks cannot be performed without off-board equipment.  After 25 years of architecting diagnostics, diagnostic testing and hardware/software for a major domestic OEM and external clients, I haven’t seen a case where the scan tool could come close to singularly providing the necessary tests for a technician to properly perform power/energy tests, and charging, balance, or condition the battery pack system.  Enough said on the scan tool.        

A Scenario for an Aftermarket Battery Pack Service Business
A likely scenario for an aftermarket HEV battery pack service business is that they will be servicing customer vehicles with various levels of mileage.  Mileage is not a good indicator or predictor of battery pack state-of-health (SOH).  Mileage is also not a predictor for any battery packs that have been purchased used/salvage that are removed from a vehicle and placed in storage.  However, the length of time that a battery pack has been dormant (no discharging/charging) is a major predictor on its capacity and cell-to-cell balance.  When the battery pack is received by the service business (whether in the field or otherwise) it may have been in a vehicle with 50k miles or 250k miles and the condition of the vehicle (and HV battery pack) is likely unknown.  Therefore, all battery packs must be treated with the same testing regimen irrespective of their mileage. 

Experience has shown than if a HV HEV battery pack has only 50k miles this by no means guarantees the condition of the battery modules (20 to 40 battery modules depending on model year, manufacturer and vehicle model).  Even if the HV battery pack were in a vehicle when it arrived at a service shop and a serial data (scan) tool could be connected to the vehicle to gain access to the battery pack controller there will not be enough data nor tests available through the serial data tool to properly test and analyze the battery pack for diagnosing, reconditioning, rebuilding or, remanufacturing.  The serial data tool is a wonderful tool for checking general battery pack SOH but lacks serious capability in performing industry standard power and energy testing processes.  Also, with NiMH battery modules there is no direct correlation between battery module terminal voltages and state-of-charge (capacity).  Determining actual NiMH (or Lithium Ion) battery power and energy becomes a very difficult task unless you have the proper battery testing equipment and associated training.  This is contrary to Lead Acid battery technology in which state-of-charge can be more easily determined by correlating battery terminal voltage.  Therefore, a new approach must be used to determine battery pack/ module SOH.  Based on this information, if an automotive service business is not determining the battery pack SOH prior to customer purchase and shipping the product, the service supplier would be sending product with unknown SOH.  Wouldn’t a much more prudent process be to install a battery pack with a quantified (known) power and energy SOH?  Not to mention that customer confidence in the product that the supplier (e.g., your remanufacturing business) would be of significant value to the customer when the possibilities of failed parts or parts that fail within a warranty period are at stake.  So, the question becomes:  How can an automotive service business determine HV HEV battery pack power and energy SOH before selling the conditioning service or used unit to a customer? 

What’s This Power and Energy Test Stuff, Anyway?
Battery Power Testing
A power test determines how much electrical power can be delivered to the electric propulsion system. This important metric determines how much electric assist (torque/hp) during an acceleration event the motor(s) in the electric propulsion system can provide to the engine. This test will assist in determining battery cell resistance that could affect the power delivered by the battery pack.  However, a battery pack may be power limited but not energy limited (or vice-versa) - a key analysis and diagnostic metric for vehicles that have lack of power complaints. Therefore, both power and energy tests must be performed.  Battery pack power level effects acceleration performance and overall fuel economy of an HEV or Plug-In HEV vehicle.  A battery discharger unit (BDU) that performs both power and energy tests is the industry standard for testing and conditioning battery packs. 

There are many instructors teaching the use of light bulbs to test battery packs and many technicians are using this method.  Not only is this method useless in providing accurate testing but it will damage the battery modules.  In fact, our company evaluated this method and found that, when we started with a known qualified battery pack, the light bulb method actually made the battery pack condition worse at the conclusion of the process.  Other technicians are using electric water heater heating elements to test the battery packs.  This is another method that will not provide accurate data and could damage the battery modules.  Sometimes cheap methods are just cheap but in this case it can damage a battery pack worth thousands of dollars.  Do yourself and your business a big favor.  Learn the correct methods of testing and analyzing battery packs and use the correct equipment.  It will save you from high stress, aggravation, and embarrassment with the customers.

The power test would be the first of the two tests performed as part of an SOH evaluation.  The connections to a battery module group for performing a power test are simple and are combined with laptop computer software to control the testing.  At the conclusion of the power test, the BDU will provide a signature for the user to determine each module group power state of health, and further determine how to approach any subsequent repair/rebuild of the battery pack.  Typically, the total time for a technician to perform the power test with the BDU is approximately 20 to 30 minutes for a hybrid battery pack.   
HV Battery Energy Test An energy test determines HV HEV battery pack State-of-Charge (SOC) and/or A•hr capacity of each battery module (or module group) to determine if there are weak battery cells and then compare this data to the battery specifications.  This test will also confirm the “balance” of the battery modules.  Multiple connections from each battery module group to the discharger unit for performing energy test and are controlled with a laptop computer and control software. This will determine the overall energy condition of the battery pack/battery modules. The energy test analyzes how much capacity each battery module has/is able to store and deliver (balance and capacity).  This is a key metric in how much torque the electric propulsion system can produce to assist in the internal combustion engine or how long the vehicle can operate in an electric-only mode.  This test is can also be used as an indicator to predict how close a battery module (or module group) is to triggering a Malfunction Indicator Light (MIL) and associated diagnostic code.  This is an important metric to mitigate a future customer problem with the battery pack.   

Energy storage (capacity) and power availability in the battery pack modules effect acceleration performance and overall fuel economy of an HEV or Plug-In HEV.  A recent example is the lawsuit successfully litigated by Heather Peters, relative to Honda Civic HEV battery pack performance, illustrates how (lack of) HV HEV battery system can effect vehicle fuel economy and performance. 

The total time for the BDU to perform the energy test is approximately one (1) to 1 ½ hours for a typical hybrid battery pack.   Actual technician time to perform battery connections and execute the test is approximately 10-15 minutes.  At the conclusion of the Energy Test, the BDU will provide a signature for the user to determine each module group A•hr capacity and SOH.  The signature is necessary to further determine how to repair/rebuild the battery pack (i.e., which modules need to be conditioned, how much conditioning is necessary and if replacement is necessary).

HV Battery Charging
After completion of an energy test the battery pack may or may not require additional conditioning.  In either case it will need to be charged before the next condition cycle or before being reinstalled in the vehicle.   A programmable HV battery charger will be needed to quickly recharge the battery to the proper SOC (State of Charge) level.  By programming the charger with specified data the HV battery pack will be properly charged without fear of destroying it and it will be at the proper SOC level. 

The time necessary to charge a HV hybrid battery may be two (2) to four (4) hours depending on its condition and if it needs significant reconditioning care.  The key point for where time would be allocated is the approximate 10 – 15 minute technician time to reassemble the battery, program the charger, and start the charging.  The charger programming will control the charging process and stop the charging automatically at the appropriate time. 

Let’s Summarize
In summary, there is a tremendous opportunity for automotive service business to consider testing and analyzing used HV hybrid battery packs for the purposes of diagnosing, reconditioning, rebuilding, or remanufacturing the unit.  There is an advantage for any business to consider expanding their business revenue stream to include testing and qualifying HV HEV battery packs because, customers would value knowing the SOH information accompanied by a warranty that both the customer and the business supplying service can be comfortable in assuming (e.g., 6 to 12 months).  This removes all of the battery performance unknowns for both parties.  Additionally, there is battery pack performance data (provided by the BDU software) that can be supplied to the customer that graphically illustrates the performance of the component they purchased.  The service shop can also store the performance data in their electronic system for warranty purposes or future reference.  

The NiMH battery modules are extremely resilient in providing high levels of power and energy over long periods.  Typically, only battery pack reconditioning is necessary to ensure near new or very acceptable levels of power and energy capability. Therefore, no part replacements are necessary unless otherwise desired by the rebuilding or diagnostic process.  The total time that a technician is actually on the battery pack performing testing, analysis, battery pack disassembly and reassembly is approximately one (1) hour – battery type dependent.  A very similar process can be utilized for HV HEV or electric vehicle (EV) platforms containing Lithium Ion battery pack technology systems.  The remainder of the time the process is controlled by the BDU or HV charger software.  Therefore, the entire process and associated procedures is not a labor/employee intensive proposition for a business owner.

Finally, you need to ask yourself these key questions:  1) do I want to enhance my business profitability by extending additional services to hybrid vehicle owners by offering battery pack diagnostic, conditioning, and related services?, 2) do my (current or prospective) customers desire to purchase qualified (i.e., tested) HV, HEV or, EV battery packs? 3) Do I want to offer these qualified HV battery packs to my customers in lieu of installing new or rebuilt battery packs purchased from a rebuilding supplier? and 4) where can I acquire the proper training and equipment so that my shop can begin to perform hybrid battery analysis, testing, and/or rebuilding?  My experience indicates that customers would be very interested in qualified HV hybrid battery packs with documented performance data and a solid warranty that are available at a much lower price point.  So, why don’t you start today?  There is a great business opportunity that awaits your service business!  By visiting www.go2hev.com you can secure additional information supporting your decision on how to best move forward.         

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