Hybrid Battery Testing, Conditioning & Rebuilding

At the heart of an HEV is its High Voltage (HV) battery. These battery units power the electric motors that ensure a smooth drive. All batteries will deteriorate over time which, in turn, adversely affects a hybrid vehicle’s fuel consumption as well as reduce the vehicle’s ability to accelerate, resulting in error lights. In some cases a weak battery prevents even the cranking/start of the vehicle. This is especially true in some Toyota models where there is no separate starter motor to crank up the engine and the vehicle depends solely on the battery and drive motor to crank up the engine!

The reasons behind such symptoms are complex and require specialized tools to isolate and diagnose. Most hybrid vehicles for instance run on Nickel-Metal Hydride (NiMH) HV batteries.


Popular models that run NiMH HV batteries include Toyota’s Prius and Aqua, and Honda’s Insight, Fit and Vezel.

NiMH battery packs are popular because of their resilience and capability of providing high levels of power and energy over long periods. They do however have drawbacks:


HV NiMH batteries ‘age’ and lose their power and capacity and deteriorate overtime due to:


HV NiMH battery packs are modular (the Toyota Prius, for instance, has 28 modules with 6 cells each) in their build and can suffer from modular power and capacity imbalance, leading in turn to poor vehicle performance that culminates in an error indicator.

Until Hybrid Hub, hybrid vehicle owners were left with two unappealing solutions:

At Hybrid Hub, we possess the diagnostic tools and technical expertise required to see what internal components of the vehicle’s HV is behind the drop in performance. We do this at the battery’s modular level, seeing which of the battery’s modules is causing the overall dip in performance. By restoring and balancing the output from underperforming modules, we are able to “condition” the NiMH battery packs to perform at up to 95% of its original capacity.

The diagnostics and rebuilding process is designed around GEN III Battery Conditioning BDU and Control Software, a proprietary tool designed by QTS (USA).

The BDU test unit tests the Power and Energy capabilities of the following HV battery pack systems used in most HEVs:

  • Nickel-Metal Hydride or Lithium Ion based hybrid electric vehicle (HEV)
  • Plug-In Hybrid Electric Vehicle (PHEV)
  • Extended Ranged Electric Vehicle (EREV)
  • Battery Electric Vehicle (BEV)
  • Fuel Cell Electric Vehicle (FCEV)

The GEN III BDU connects directly to each individual battery module (or module group) of a HV battery pack and performs data acquisition via QTS’s proprietary control software. This is a superior method of testing compared to using an ordinary vehicle scanner used by most workshops to study the battery pack system. The Gen III BDU unit is used to test, analyse and condition a HV battery pack, and for determining an accurate and documentable State-Of-Health (SOH) analysis. This forms the basis of Hybrid Hub’s five step rebuilding process on high voltage batteries.

Hybrid/Electric Stress Test

Generally, a customer would bring in a vehicle showing error indicator lights. A Stress Test is performed in cases where there is no error light displayed and the customer is experiencing poor acceleration and noticeable increase in fuel consumption. This test is performed without removing the battery in a very short time. The vehicle is then put through a controlled stress test where various data points are captured. Our team will then use proprietary software to determine if the battery actually requires further testing and conditioning.

Power Test and Conditioning

Step 2 is performed only if the data acquired at Step 1 shows the need for further investigation. In step 2, Hybrid Hub technicians will perform two tests.

  • Battery Power State-Of-Health (SOH) evaluation
    For this test, the HV battery back is safely removed and thoroughly checked by our technicians to ensure no Potassium Hydroxide (KOH), electrolyte leakage or corrosion has impacted the physical structure of the pack.The power test connects the individual battery pack modules of a HV battery pack to the AR&D Micro Processor controlled BDU unit and these modules are then subjected to a controlled load test by an AR&D trained Hybrid Hub technician to simulate real world driving loads on the battery.This Power Test evaluates the power voltage capability of the battery pack at a modular level, determining how quickly and effectively the battery modules inside the pack can transfer electrical energy to the electric drive motor for propulsion.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.
  • Battery Conditioning
    Battery modules with low power levels and modules that are out of balance are identified and are cycled through our proprietary BDU “Battery Conditioning” process on a modular level by our expert technicians.

Battery Energy Capacity State-Of-Health (SOH) evaluation

At this level, every module of an individual battery pack is put through a microprocessor controlled Energy Test using the proprietary AR&D software.

  • The Energy Test will determine the overall energy condition and balance of the battery modules indicating how much energy capacity each battery module has, and is able to store and deliver to the electric propulsion system. The Amp-Hour capacity is compared with the manufacturer specifications.The energy test result is a key metric in assessing 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 (EV) mode
  • Battery Conditioning – Battery modules with low energy capacity levels and modules that are out of balance in terms of capacity are identified and cycled through our proprietary BDU “Battery Conditioning” process at a modular level by our expert technicians

HV Battery Charging

After completion of an energy test and “battery conditioning”, a programmable HV battery charger controlled by proprietary AR&D control software is used to quickly recharge the battery to the proper SOC (State-Of-Charge) level.  By programming the charger with specified charging algorithms the HV battery pack is properly charged without fear of destroying it in order to restore it to the manufacturer-specified SOC level.


While most (NiMH) HV battery modules can be conditioned and restored by AR&D’s proprietary BDU and software, certain modules may be identified as ‘capacity dead’ – i.e. beyond repair by the energy test signatures. In such cases, rebuilding involves replacement of capacity dead modules. This is the only time a replacement of any parts are done in our process.

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