Hybrid Battery Pack Issues? Here’s What You Need to Know

Manufacturers of hybrid battery packs typically guarantee that their products will function as intended for 8 years, although one manufacturer recently increased this period to 10 years. In fact, hybrid battery packs that still work perfectly after 12 to 15 years of normal use are not uncommon. Broadly speaking though, all hybrid batteries pass through three distinct phases during their lifetimes, these being the-

Healthy phase

During this phase that typically lasts between 3 and 6 years of use, the battery performs as intended and full battery power is always available.

Weakened phase

This phase can start at any point between 3 and 6 years of use (approx. 100,000 km). During this phase, the battery starts to degrade, and progressively more energy is required to keep the battery in an acceptable state of charge as the battery becomes progressively more degraded.

Failed phase

This phase can start at any point from between about 5 years and 11 years of use (approx. 200,000 km), but unlike the previous two stages though, the failed phase is clearly defined. The final phase of a hybrid battery's life typically starts with the appearance of one or more battery-related trouble codes and typically ends when one or more control systems prevent the internal combustion engine from starting to protect critical control systems and components.

Note that an enforced no-start condition will persist until the battery is repaired, reconditioned, or replaced, which begs this question-

To understand how and why hybrid battery packs fail, it is necessary to understand how hybrid battery packs are constructed. Note though that although there are some differences between hybrid battery packs in terms of the capacity, size, and the number of cells in the battery pack, all hybrid battery packs are sufficiently similar in terms of their overall design and construction to fail in the same way, and for largely the same reasons.  

We need not delve into the complexities of battery chemistry here, but suffice it to say that a hybrid battery pack can contain anything from 120 to more than 200 cells that are connected in series. This means that the capacity of the first cell is added to the capacity of the second cell, until (typically) six cells are connected to produce what is known as a “module”.

The modules are then also connected in series; i.e., the capacity of the first module is added to that of the second module, and so on to eventually produce a battery pack that can have a capacity of anything between 100 volts and 300 volts, depending on the overall battery design. As the battery ages however, the combination of repeated charge/discharge cycles and less-than-perfect connections in the battery pack begins to change how electrons flow through some cells.

The practical effects of these changes are that a), the weakest cells begin to discharge faster and take longer to recharge than the strongest cells, and b), that the battery becomes “unbalanced” in the sense that some parts (cells or modules) of the battery have a higher or lower state of charge than other parts.

If this condition is allowed to persist over extended periods, the changes in individual cells can become large enough to change the polarity of affected cells, which has the practical effect of destroying the battery pack, which brings us to-

This procedure is highly technical, and performing it successfully requires both expert knowledge and highly specialised equipment that includes advanced diagnostic, analytical, and charging equipment.  Briefly, the procedure follows this general pattern-

If no battery-related fault codes are present on the vehicle, the battery is discharged with a specialised discharging device to break down the battery’s charge memory. The battery is then recharged with a specialised charging device and tested again to identify bad cells and/or modules. The discharge/charging cycle is repeated several times to ensure that all the cells in the battery are in a balanced stateIf however, hybrid battery-related fault codes are present on the vehicle, defective cells and/or modules are removed from the battery pack and replaced with either new or known-good components to restore the battery's balance

For the most part, reconditioning a hybrid battery pack can restore a battery pack’s efficiency. However, whether or not this happens depends on several caveats or pre-conditions, including the following-

The battery pack must be in a condition that allows reconditioning. For instance, melted, exploded, fractured, or impact-damaged batteries typically cannot be reconditioned, and are best replacedThe reconditioning procedure is performed by trained, skilled, and knowledgeable technicians who have access to the required equipment, dealer-level service information, and new or at least, known-good battery parts/components if parts replacements are required to complete a reconditioning procedure successfullyThe service provider has the knowledge, skill, and equipment required to diagnose and repair faults elsewhere in the hybrid system that can (and often do) either cause or contribute to severe imbalances in hybrid battery packs

This last point is particularly important because it speaks to hybrid battery maintenance and/or servicing procedures, all of which should and must form an integral part of-

While the words/terms “hybrid battery reconditioning”, “hybrid battery repair”, and “hybrid battery service” are often used interchangeably, the fact is that to battery service professionals, these terms have very specific meanings and definitions.

For instance, while the terms “battery reconditioning” and “battery repair” are often mutually inclusive, “battery reconditioning” more accurately refers to restoring a hybrid battery pack’s balance, while “battery repair” refers to the procedure of removing and replacing battery cells and/or modules. In practice though, both the above procedures can be described as both reconditioning and repair and the one can often not be performed without performing the other, as well.

“Battery service” on the other hand, typically refers to ensuring that all the systems that support the proper operation of the hybrid battery are fully functional. These types of procedures typically include checking, inspecting, diagnosing, and/or repairing a), wiring, control modules, fuses, relays and other components that are external to the battery, and b), ensuring that the battery’s cooling and temperature control systems/mechanisms are fully functional, which brings us to the topic of-

Reconditioning

Depending on the age and overall condition of a hybrid battery pack, reconditioning might be an option provided the battery has not sustained physical damage or has not overheated repeatedly.

Having said that, it should be borne in mind that reconditioning may have to be repeated at least once every 12 to 18 months. If more frequent reconditioning than once every 18 months or so is required, the battery may be defective, at which point you might want to consider-

Repairing

Repairing a battery typically involves replacing cells and/or modules, followed by a reconditioning process to restore the battery's balance. Battery repair is typically more expensive than reconditioning.

Here at DrHybrid, our core business is repairing, reconditioning, and/or replacing hybrid battery packs. We have the skills, knowledge, and technical expertise to diagnose battery related issues on hybrid vehicles. More importantly, we use advanced technology and equipment to analyse, diagnose, repair, and recondition hybrid batteries of all types and descriptions.

We also realise that the battery pack may be the most expensive component on hybrid vehicles, so before we replace a battery pack we first scan the entire vehicle for faults in the hybrid system since in some cases, a battery pack can fail as the result of faults and defects in battery-related and/or ancillary systems like for example, the battery's cooling system.

So if you are having issues with the battery pack in your hybrid vehicle, why don’t you give us a call? We can tell you not only what the problem is, but also what we can do to fix the problem.