How Does Hybrid Battery Conditioning Work?

VW Tiguan GTE Concept. Image courtesy of VW Global Media.

VW Tiguan GTE Concept. Image courtesy of VW Global Media.


What is Hybrid Battery Conditioning—A Deeper Look

The conditioning process begins with removing the NiMH (nickel–metal hydride battery) battery pack from the vehicle. Specialized THS (The Hybrid Shop®) equipment is then connected to the battery pack for the purposes of rendering two categories of tests; The Power Test and the Energy Test. Data is then collected by the equipment controller for analysis and diagnostics.

THS specialized equipment consists of:

  • BDUIII (Battery Discharger Unit, Third Generation)
  • Laptop with THS Proprietary Software
  • Diagnostic tools (Thermal Imaging Camera, Electric Machine/Motor Tester)

Hybrid Shop Battery Conditioning Process, courtesy of The Hybrid Shop

The Power Test

This tests the power capability of the battery pack and determines how quickly and effectively the battery modules inside the battery pack can transfer electrical energy to a load.

The battery modules are subjected to a controlled load test (monitored by THS software) of approximately 100 amps. Data is then collected by the equipment controller for analysis and diagnostics.

Proper power levels are essential for the vehicle to produce necessary acceleration performance. Battery modules with low power levels are identified and can be replaced while the battery pack is out of the vehicle.


Energy Test

An Energy test is performed to acquire the Amp-hour capacity of each battery module by placing a controlled load (monitored by THS software) across each battery module/module grouping.

At the conclusion of the Energy Test, the State of Health (SOH) for each module is provided in a hard copy report that will assist in determining how to repair/rebuild the battery pack.

Energy capacity levels of the battery modules significantly effects vehicle fuel economy and acceleration performance and there is a direct correlation between battery Energy and fuel consumption.


Analysis, Diagnostics, and Conditioning

Once the results of both tests are analyzed, the battery modules are “cycled” (using a controlled charging and discharging processes) to increase the power and capacity of the modules. The power of each battery module is completely discharged and then brought back up to full capacity.

This is called cycling and is performed at least twice before the battery is completely “conditioned”.
The capacity of most NiMH battery modules/module groups can be increased to approximately 92-95% of a new battery module by using the cycling process.


Energy Test Failure

If any of the battery modules fail to provide proper Energy capacity, a simple replacement of the individual non-performing battery modules can be accomplished to increase the Energy performance of the battery pack.


The Longevity of a Conditioned Battery

If the vehicle battery management system software is operating properly, a properly Conditioned battery pack can maintain its capacity and balance for many years but, its longevity is dependent upon:

  • Age of the battery pack at the time of Conditioning
  • Geographic area in which it has operated – ambient temperatures and/or elevations, or its driving cycle (i.e., does the vehicle remain unused for periods or is it used daily or, is it driven on highway or city/suburban driving cycle)
  • The battery pack been permitted to be operated in a deeply discharged state by its owner/operator, or it has been serviced incorrectly by an untrained technician
  • Amount of electrolyte leakage


A NiMH battery can be conditioned many times and this process does not degrade the integrity of the battery pack.


Malfunction Indicator Lamp (MIL) Warnings

Most initial and mid-range battery pack performance problems will not cause the Malfunction Indicator Lamp (MIL) to illuminate on the dashboard to inform the driver that there is a problem. The only indication that there are problems with battery pack Power or Energy is the driver would notice a reduction in vehicle performance and fuel economy – well before the MIL is triggered. The MIL will trigger when there are more catastrophic (chronic) problems and the battery pack is near failure.

If most battery pack problems are identified before the MIL is triggered, it can usually be Conditioned to a state of good health. The MIL will typically not be triggered for intermittent or reduced battery pack performance. This is one of the primary reasons of why long-term scheduled NiMH battery pack conditioning is important to enhancing the life-cycle of the battery pack, and reducing the overall cost of HEV ownership.


Battery Pack ModuleReplacement and Rebuilding

Conditioning a battery pack traditionally is defined as battery pack testing only, with no components replaced. Simply stated, there are no hardware or battery module components replaced as part of a battery pack Conditioning process.

If the Conditioning process identifies battery modules that need to be replaced, the process would move into the realm of battery pack rebuilding. However, if Conditioning is scheduled properly through the lifetime of the vehicle, the necessity of replacing battery modules is minimized.


HEV Electric Power Model, courtesy of The Hybrid Shop

This is another valuable post from TheHybridShop.comHECN is happy to welcome the, a new green automotive startup, as our first Service Advisor.  The mission of The Hybrid Shop is to “provide the highest quality maintenance, service and repair experience for hybrid electric vehicle owners.” Read more about them and servicing hybrid electric cars here.  You can also find them on FacebookTwitterLinkedINGoogle Plus, and YouTube.

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