The Science of Hybrid Battery Conditioning and How it Works

What is Hybrid Battery Conditioning? — A Deeper Look

The conditioning process begins with removing the nickel–metal hydride (NiMH) battery pack from the vehicle. Specialized Hybrid Shop® equipment is then connected to the battery pack to render a Power test and an Energy test. Data is then collected by the equipment controller for analysis and diagnostics.  The whole process takes several hours and should only be performed by experienced and trained Hybrid Shop® technicians.

Click on the links to discover answers to following questions:

Why and When does a HEV battery need to be serviced?

If your are experiencing any of the following symptoms, this would be an indication that your vehicle would benefit from a conditioning service:

  1. Poor Gas Mileage: If you’re noticing your HEV’s gas mileage isn’t as effective as it once was, there is a very good chance your battery needs to be looked at.
  2. Lack of Power: If you’re struggling to find the power to get over hills and accelerate as you once did using your HEV, then you likely have a battery issue.

Because your HEV’s service light will generally not turn on when your battery starts to under perform, it’s important that you’re aware of your vehicle’s gas mileage and performance.  This awareness may be the first indication that a service is needed.

Conditioning Process

Hybrid Battery life: how to make them last longer

Today’s hybrid vehicles come equipped with a nickel-metal hydride battery pack that powers the car’s systems. As all batteries lose power over time, The Hybrid Shop offers a process called “conditioning” that effectively restores a used battery back up to 95% of its original charge. Below is an explanation of how we condition a battery.

A closer look: Battery Conditioning Process

 Want even more information? Here you go!:

  1. Power Test
  2. Energy Test
  3. Diagnostics and analyzing the results
  4. Cycling/conditioning process
  5. Longevity of a conditioned battery
  6. MIL warnings
  7. Energy test failure
  8. Replacement and rebuilding

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 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 conditioned (or replaced, if necessary) 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 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 assists in determining how to repair/rebuild the battery pack.

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

Diagnostics, Analyzing Test Results, and Conditioning

Once the results of both tests are analyzed, the battery modules are subjected to  a controlled charging and discharging process 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 process is performed at least twice before the battery is considered completely “conditioned.”  Through this process, the capacity of most NiMH battery modules/module groups can be increased to approximately 92-95% of a new battery module.

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 and its driving cycle (i.e., does the vehicle remain unused for periods; is it used daily; is it driven on highways or primarily in cities or suburbs)
  • Level of charge/discharge – operating in a deeply discharged state adversely affects longevity of the battery pack
  • Quality of previous services – improper or sub-par services provided by untrained technicians can negatively impact how long the conditioned battery will last
  • Amount of electrolyte leakage

A NiMH battery can be conditioned many times without degrading 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. The only indication a driver would have of a battery-related problem would be a reduction in vehicle performance and/or fuel economy – well before the MIL is triggered. The MIL only comes on when there are more catastrophic problems and the battery pack is near failure.

This failure of the MIL to alert drivers to early battery issues is the primary reason why regular, scheduled check-ups of hybrids are so important. If most battery pack problems are identified before the MIL is triggered, it can usually be conditioned to a state of good health.  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.

Energy Test Failure

If any of the battery modules fail to provide proper energy capacity, individual non-performing modules can be replaced to increase the overall energy performance of the entire pack.

Battery Pack Module Replacement 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.

Here’s a diagram of the HEV Motor demonstrating the flow of power.

THS HEV Electric Power Model.jpg

Electrical Vehicle Diagram