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You likely have questions about our hybrid battery conditioning and maintenance services. Below, are the ones we hear most often.

What is the difference between a Hybrid Vehicle Battery and an Electric Vehicle Battery?

What is the difference between a hybrid vehicle battery and an electric vehicle battery?

Hybrid vehicles and battery electric vehicles (BEV or EV) have two main things in common, electric motor-generators (MG) and a battery pack. The battery pack, in both cases, is like the fuel tank in a conventional vehicle, storing energy to power the MG and vehicle electrical systems. Unlike the fuel tank in a conventional or hybrid vehicle, however, the battery pack can also be recharged by the car itself, via the MGs.

At their most basic level, electric vehicle and hybrid vehicle battery packs are a collection of rechargeable cells arranged to hold a specified amount of energy. In this way, they are identical. On the other hand, there are a couple of key differences in chemistry, charging capabilities, and maintenance.

Chemistry and Capacity

The main difference between hybrid vehicle and electric vehicle battery packs is their chemistry. For example, the 2010 Toyota Prius NiMH (nickel-metal hydride) hybrid battery pack holds just 1.3 kWh (kilowatt-hours). This is enough to power the MGs for a maximum of a couple of miles stop-and-go traffic in EV-Mode. The 2012 Toyota Prius Plug-In, on the other hand, features a Lithium-ion (Li-ion) hybrid battery, which is about twice as energy-dense as NiMH. Thus, the Prius Plug-In’s 4.4 kWh Li-ion battery pack, at 330 lbs, weighs three times more than the 1.3 kWh NiMH pack in the Prius, yet offers fifteen times more EV-Mode range, up to 15 miles in certain circumstances.

Finally, in electric vehicles whose sole energy source is the battery pack, we see a significant jump in battery capacity. The 2015 Nissan Leaf, for example, is equipped with a 24 kWh Li-ion battery pack, featuring an average range of 84 miles. The Tesla Model S 85 kWh, on the other hand, has a range of about 300 miles. Making the switch to Lithium-ion rechargeable battery chemistry makes this possible, because NiMH or SLA (sealed lead acid) batteries would be too heavy.

Charging Capabilities

The other main difference between hybrid vehicle and electric vehicle battery packs is how they are charged. Hybrid vehicles, such as the Toyota Prius and Ford Fusion Hybrid, do not feature a charge port for the hybrid battery. Instead, they are charged by the MGs, driven by the ICE or during regenerative braking. Plug-in hybrid vehicles, on the other hand, feature a charge port for their small hybrid battery packs. The Prius Plug-In, for example, takes about 90 minutes to charge on an LII (Level 2, 240 V, 30 A) charging station. Once the 15 miles of EV-Mode capacity is used up, the car reverts to regular hybrid vehicle operation, using a small part of the hybrid battery capacity for improved fuel economy and stop-and-go traffic performance.

Electric vehicle battery packs, which have the largest battery capacity, can only be charged by electric vehicle charging stations and, to a lesser degree, regenerative braking. The Nissan Leaf’s 24 kWh battery pack, for example, takes about four hours on an LII charging station, or as little as thirty minutes on an LIII (Level 3, 480 V, 3 Φ, 125 A) charging station. On an LIII charging station, Tesla Model S 85 kWh can fully charge in about an hour.

AAA Hybrid Battery Repair

AAA Hybrid Battery Repair has proven scientifically that hybrid battery conditioning is a cost-effective solution to restore hybrid vehicle performance and fuel economy. Battery conditioning, however, only applies to NiMH battery chemistry.

Some plug-in hybrid vehicles, and most battery electric vehicles, are powered by Li-ion battery packs, which cannot be conditioned. When Li-ion battery capacity and power performance wane, new or rebuilt battery packs are the only viable options. The Hybrid Shop can determine which modules require replacement, rebuilding an electric vehicle battery pack being typically less-expensive than buying a new battery pack.

Will a Hybrid Battery last as long as a Standard Battery?

Hybrids Usually Use Two Types of Batteries

Hybrid electric vehicles (HEVs) have two batteries. Like a normal car, they have a low-voltage battery that powers systems such as the stereo, computers, and navigation system. They also have a high-voltage battery, called the traction battery, that powers systems like the vehicle’s electric motor-generator unit and air conditioning compressor. The traction battery is the expensive one because of its complexity and the exotic materials required to construct it. Most people know how long to expect their car battery to last, so a common question is whether or not their hybrid battery will last as long as their standard battery.

So… What’s the Difference? Why do Car Batteries Fail?

The low-voltage battery in a hybrid vehicle is a sealed lead-acid (SLA) battery. These are heavy but relatively simple. Without going into too much detail about their construction or electrochemistry, they’re constructed of a series of lead plates separated by an electrolyte, in this case, a solution of sulfuric acid and water. When the battery is discharged, lead sulfate forms on the surface of the plates, releasing stored energy and gradually reducing the surface area of the plates and the battery’s power. During charging, this substance is dissolved, and the battery’s sulfuric acid level rises back to normal. Over time the sulfate crystallizes and can no longer be dissolved during charging, degrading the battery’s overall capacity permanently. For a typical driver, under optimal conditions, an SLA can be expected to last about 3-6 years, though even a single deep discharge can ruin it, no matter its age.

The traction battery in most hybrids is a Nickel-Metal Hydride (NiMH) battery. These are constructed of cells composed of nickel and metal hydride plates, separated by a potassium hydroxide electrolyte. Over time, barring the battery being overheated or physically damaged, NiMH batteries “go bad” because a resistive layer of crystals forms on the surface of the nickel. As with SLA batteries, time is more important than mileage to this process, and driving conditions and habits are more important than either. Under typical conditions, NiMH batteries are expected to last about 5-10 years, though prolonged rest periods or getting overheated by strenuous charging and discharging cycles (such as when driving in mountainous terrain on a regular basis) can shorten that life expectancy.

Can Anything Be Done To Extend the Life of a Hybrid’s Batteries?

In the case of the vehicle’s low-voltage SLA battery, unfortunately, the answer is a conditional “no.” Proper maintenance, driving the vehicle daily, or putting the battery on a trickle charger during long storage periods can maximize the battery’s life expectancy, but once the sulfate is crystallized over most of the surface of the lead plates, the battery can’t be revived as a whole unit and must be replaced. Fortunately, SLA batteries are made of fairly common materials and are thus reasonably affordable.

Traction batteries, on the other hand, are more advanced and made of rarer materials. This makes them anything but affordable, with the cost of replacement ranging from $2,500 to $8,000 or even more! Fortunately in the case of NiMH batteries in particular, in most cases, the battery can be revived as a whole unit without needing to be discarded or remanufactured. For about a third-to-half the cost of a new battery, AAA Hybrid Battery Repair can restore up to 95% of a NiMH battery’s initial power, energy, and life expectancy through a proprietary, scientifically-developed process called conditioning.

By cycling the battery between 0% and 100% states-of-charge (the vehicle’s computer keeps it between 38% and 82% for various reasons beyond the scope of this article), the resistive layer of crystals can be broken up and the battery’s performance restored. In laboratory settings, NiMH batteries have been shown to be able to be conditioned many, many times. It generally only takes 2-3 cycles to restore a NiMH traction battery to like-new condition. That means if a given hybrid’s battery only needs to be conditioned every 4-7 years, the battery can theoretically outlast the very vehicle it powers and should never need to be replaced.

Which Hybrid Battery is better, Nickel-metal Hydride or Lithium-ion?

Which hybrid battery is better, nickel-metal hydride or lithium-ion?

In terms of hybrid battery technology, the lithium-ion battery (Li-ion) is the newcomer. Nickel-metal hydride battery (NiMH) technology has been around for decades and is very reliable chemistry. Regarding various battery chemistries, the key for hybrid vehicles, as well as electric vehicles, is the correct balance between energy density, battery longevity, and power delivery.

The typical sealed lead-acid (SLA) 12 V battery under the hood of a conventional vehicle is very reliable, can deliver loads of power, can be cycled hundreds of times, and lasts for a long time. In a hybrid vehicle, however, an SLA battery would be poorly suited because it isn’t very energy-dense. In other words, an SLA hybrid battery pack would be so heavy that it would outweigh the benefits of the hybrid powertrain. Just for comparison, the average SLA battery can hold about 35 Wh/kg (watt-hours per kilogram) and deliver about 180 W/kg (watts per kilogram) of power.

Nickel-Metal Hydride

With the introduction of the Toyota Prius, Toyota chose NiMH hybrid battery technology which is far better suited to hybrid vehicle applications. Toyota’s NiMH battery pack holds, depending on model year, up to 46 Wh/kg and can deliver up to 1,310 W/kg power. This energy- and power-density combination enabled the first Toyota Prius hybrid vehicle to achieve 41 mpg. For 2015, Toyota expects to break 55 mpg with the fifth-generation Prius.

Aside from the excellent energy and power capabilities that the Toyota Prius hybrid battery offers, the nickel-metal hydride is also a resilient battery chemistry. Typical NiMH batteries can be cycled up to many, many times but will always eventually degrade. If SLA battery performance starts to degrade, the only option is recycling. When a NiMH battery pack begins to degrade, however, it’s still possible to restore its performance, via battery conditioning.


The latest reliable battery chemistry to be developed is lithium-ion, which is already ubiquitous in the world around us, from smartphones to laptops and even electric and hybrid vehicles. Li-ion hybrid battery technology, such as that used in the Ford Fusion Energi plug-in hybrid vehicle, holds about 250 Wh/kg, 7x better than an SLA battery, even 5x better than NiMH, and it can deliver up to 1,000 W/kg.

Additionally, lithium-ion has been proven to cycle at least as well as nickel-metal hydride, a good candidate for hybrid vehicle battery packs. Some newcomers to the hybrid vehicle market are adopting the new technology including different variations of lithium-ion battery technology, such as LCO, lithium-iron phosphate (LiFePO4), and lithium-polymer (LiPo).

Building a “Better” Hybrid Vehicle

While Toyota has held out on making the switch to Li-ion battery types in its hybrid vehicle lineup, except for the Prius Plug-In, it seems that fuel economy and hybrid battery capacity considerations may eventually lead to more Li-on vehicles. But NiMH battery technology will be around for many more years. Li-ion hybrid battery chemistry holds more energy and delivers more power, and seems to be just as reliable as NiMH, which makes it far easier for automakers to justify its adoption.

Still, like all rechargeable batteries, Li-ion hybrid battery performance degrades over time.

Are there different kinds of Hybrid Batteries?

Are There Different Kinds of Hybrid Batteries?

There are two main types of high-voltage traction batteries used in hybrid electric vehicles today, each with its own advantages and disadvantages. By far the most common type is Nickel-Metal Hydride (NiMH). Many plug-in hybrids and electric vehicles use Lithium-Ion (Li-Ion) batteries instead, even though it is a newer and less-proven technology for vehicle applications. This is because Lithium-Ion batteries have a much greater energy density or energy per unit mass. This means for a given energy requirement, they are lighter. In an electric vehicle or plug-in hybrid vehicle, which requires enormous amounts of reserve power, the weight differential can result in extended range and improved efficiency.

Despite this, the Li-Ion batteries aren’t widely in use in normal hybrid vehicles for several reasons. The first is because they are dangerous. They contain a flammable electrolyte because water-based electrolytes don’t have high enough conductivity for the voltage produced by a single cell of a Li-Ion battery. They also swell when in a high state-of-charge, so to keep the swelling under control, Li-Ion batteries are kept under pressure. For consumer electronic applications, this isn’t too great a concern, because they aren’t typically used in conditions which could cause them to rupture, plus the low power needs of portable electronics means that their batteries are small. The battery pack in an electric or plug-in hybrid vehicle, on the other hand, is very large, and there is a chance that it could eventually be subjected to rupturing conditions such as a vehicle collision.

Nickel-Metal Hydride batteries have lower energy density than Li-Ion batteries but are still much better than most other battery technologies. They are much safer than Li-Ion batteries and are more abuse-resistant, using a water-based electrolyte that isn’t flammable or pressurized. They can also last much longer, in terms of calendar life, if they’re treated well and properly maintained through a process called conditioning. Aside from their marginally lower energy density, their primary disadvantage for automotive applications is a much higher rate of self-discharge, up to 30% per month compared to 1.5% for Li-Ion. This means a hybrid vehicle with a NiMH traction battery pack needs to be driven frequently, preferably daily, as the battery doesn’t like to sit for long periods of time.

Battery Service Options

AAA Hybrid Battery Repair's expertly trained technicians are fully fluent in both types of battery technology. Unlike a dealer, which views a vehicle’s battery as a mysterious black box to be wholly replaced or left alone according to what a computer tells them, AAA Hybrid Battery Repair can perform a detailed State-of-Health analysis of a hybrid’s battery, testing the energy, power, and state-of-charge for each individual module. This allows for individual damaged cells to be replaced at a large saving over the cost of a new battery.

For Nickel-Metal Hydride batteries, AAA Hybrid Battery Repair also offers proprietary, one-of-a-kind battery conditioning service. For all hybrid batteries, the strength of the pack is limited to the strength of its weakest cell, so as a battery goes out of balance, with its various cells and modules providing different amounts of energy or power, only the weakest cell’s capacity matters. By balancing the cells to each other and by breaking up the resistive layer that forms on the nickel over time, battery conditioning can restore 90%-95% of a NiMH battery’s power and energy and increase life expectancy for between a third to half the cost of a replacement battery pack.

Are there problems with a Hybrid Battery that I could fix myself?

Are There Problems With a Hybrid Battery That I Could Fix Myself?

The short answer is simple: No.

Even the dealer’s technicians do not consider a hybrid vehicle’s high-voltage or traction battery to be a serviceable item. They aren’t trained or equipped to go any deeper into its diagnosis than to talk to the car’s primary computer, the Hybrid Controller, to see if it’s detected a catastrophic failure. If it has, they replace the entire battery, often needlessly. If it hasn’t, they leave it alone, even if there are problems causing decreased performance and fuel economy.

Despite that, some people really like the DIY mentality and want to try to fix their vehicles themselves. Cars are dangerous things. They’re big, heavy, and filled with a wide variety of chemicals, many of which are flammable, toxic, irritating to the skin, or worse. Even so, a conventional automobile’s risks are understood by many people and can be managed by an adventurous owner with a moderate amount of technical skill. With a hybrid vehicle, though, that simply isn’t the case. Let’s discuss just a couple of the reasons.

High-Voltage, High-Energy Systems Mean High Electrocution Risk

A hybrid electric vehicle’s high-voltage power cables are covered in bright orange insulation for a reason. It’s a warning to stay away — a warning that should be heeded — it’s a high-voltage system after all.

Physics 101: Ohm’s Law states that Current = Voltage over Resistance (I=V/R)

The human body has a resistance between 1,000Ω and 100,000Ω depending on a variety of conditions. For direct current (DC), the type of current that flows through a hybrid’s high-voltage systems, the amount of current that can cause fibrillation of a person’s heart, and subsequent death without immediate medical attention, is about 300mA. Unfortunately at 88mA, muscles contract involuntarily, making it impossible to let go of the source of the current.?

A conventional car battery produces 12.6 volts when fully charged. Since most people would consider death to be an unacceptable risk, we’ll use the worst case of 1,000Ω of resistance. Thus, the most current you can expect to experience when touching both terminals of your car’s conventional sealed lead-acid battery, is I = 12.6V / 1,000Ω, or 12.6mA. This is just enough that you might feel a slight tingling sensation in your hands and fingers. On a dry day you wouldn't even feel that. So it’s safe, electrically speaking, for an adventurous car owner to work on a conventional vehicle’s electrical systems.

A hybrid vehicle’s traction battery, on the other hand, produces much higher voltage. For argument’s sake, we’ll use the most commonly-serviced hybrid, the Second Generation Toyota Prius produced between 2004 and 2009. The Prius’ battery produces 201.6V of electrical potential. In the same scenario as above, that means the current you can expect to experience is 201.6mA, more than enough to ensure that you can’t let go once you’ve grabbed the battery or a damaged cable. “But wait,” you say, “That’s less than the 300mA required to stop my heart!” Ah, but it’s not that simple. Since you can’t let go, the current will begin to damage the skin, burning it, which can reduce its resistance to as low as 500Ω. At 500Ω, now you’re experiencing 403.2mA, more than enough to kill you. This is just one reason you should always bring your hybrid vehicle to a qualified repair shop, such as AAA Hybrid Battery Repair, any time its high-voltage components need servicing.

Safety First – Bring Your Hybrid to a Qualified Technician For All Repairs

Electrocution aside, hybrid vehicles are more dangerous to service than conventional ones for other reasons too. For example, just because a hybrid’s Internal Combustion Engine (ICE) is off, doesn’t mean it’s safe to work on. There are a number of conditions in which the vehicle’s Hybrid Controller turns the gasoline engine off, but the vehicle itself is still fully active. This means that if the Hybrid Controller decides it’s necessary, it can restart the ICE without warning. If you happen to have your hand in its workings or are beneath it with the oil filter off, this could pose various health risks.

While the dealer is certainly qualified to perform most repairs on your hybrid vehicle, only AAA Hybrid Battery Repair can perform in-depth diagnosis of the State-of-Health of your hybrid’s high-voltage systems, including the battery, motor generator, power converters, and more. And, for a third-to-half the cost of battery replacement, AAA Hybrid Battery Repair’s technicians – the most highly trained in the world to work on your hybrid vehicle – can condition your battery using a scientifically proven process, allowing you to reuse it in like-new condition for years to come.

Is it less expensive to recondition a Hybrid Battery than buy new?

Is it less expensive to recondition a hybrid battery than buy new?

As the term suggests, buying a “new” hybrid battery is exactly the same thing as what comes in a new hybrid vehicle. Constructed of entirely new rechargeable battery modules, bus bars, temperature and voltage sensors, a new hybrid battery pack will perform just as good as the original one that came in the car to begin with. Still, buying a new hybrid battery can cost between $5,000 and $10,000, depending on make and model, which makes less-expensive reconditioned hybrid batteries an attractive proposition.

Reconditioned hybrid battery packs, also referred to as rebuilt or remanufactured, are typically tested for proper operation, and defective or worn components, such as degraded battery modules or burnt-out temperature sensors, are replaced with new ones. Since most of the battery pack is original, a reconditioned hybrid battery can be significantly less expensive than a new one, but is it all it’s cracked up to be?

Reconditioned Hybrid Battery Packs: Two Caveats

While a new hybrid battery is guaranteed to perform as expected, this is only because it’s constructed of all new parts. Reconditioned hybrid battery pack performance can be sketchy if you consider what it is the rebuilder actually does. Ostensibly, each battery module would be tested for power delivery and capacity, and replacements would be ordered for those that aren’t up to task. Unfortunately, a simple voltage test or ten-second health check isn’t enough to determine a module’s health. So, there’s the first caveat: that individual hybrid battery pack modules may or may not be well-balanced with the rest of the pack.

The second caveat is that the source of replacement modules may be questionable. Early in the hybrid vehicle revolution, manufacturers, such as Honda and Toyota, weren’t very careful with their hybrid battery pack return policies, so there were many of these “spent” hybrid battery packs floating around the market. Eventually, these companies started imposing huge core charges, to make sure the packs would end up back at the manufacturer. Today, regarding Honda five- and six-cell “sticks,” or modules, there are just one or two suppliers out of China, whose quality and manufacturing standards may or may not be up to par.

When hybrid vehicle performance or fuel economy begins to suffer, or if this has gone on so long that the hybrid controller has detected a major fault and shut the system down, a shop may suggest hybrid battery replacement, at which point you’re left with the two choices above. On the other hand, AAA Hybrid Battery Repair offers an alternative — hybrid battery conditioning.

Hybrid Battery Conditioning

AAA Hybrid Battery Repair can often restore a hybrid battery to over 90% of its factory performance and capacity, without throwing away any parts, for significant cost savings.

During initial testing, if an individual module requires replacement, the process moves to rebuilding, after which the pack is conditioned to ensure that all modules are contributing equally to the pack. After all, the hybrid battery pack is only as strong as its weakest module, so leaving out the conditioning process is essentially a gamble.

Finally, hybrid battery conditioning by AAA Hybrid Battery Repair is covered by a twelve-month unlimited-mileage guarantee, unlike some refurbished hybrid batteries, which may carry as little as a thirty-day guarantee, if any at all.

What are common problems with early Honda Civic hybrid batteries?

What are common problems with early Honda Civic hybrid batteries?

Hybrid vehicles, consisting of both fossil fuel and electrical components, deliver better performance and fuel economy simply by virtue of combining the best attributes of both the internal combustion engine (ICE) and the electric motor-generator (MG). The energy for the ICE is stored in the fuel tank and, because it is refillable in just a few minutes at the gas station, it doesn’t really degrade. Of course, regular maintenance of the ICE will assure continued reliability, performance, and fuel economy. The energy for the MG is stored chemically in the hybrid battery pack, which has a limited lifespan, perhaps five to seven years before its performance begins to degrade.

Honda hybrid vehicles have been around since the beginning of the hybrid vehicle revolution, nearly twenty years ago. The average lifespan of a Honda Civic hybrid battery is most directly related to how and where it is driven. That is to say, a hybrid vehicle is best driven daily in stop-and-go traffic in a temperate climate. Honda’s hybrid control system called Integrated Motor Assist (IMA), suffered from its own design for the first couple of generations, leading to many premature failures, service programs, and even class-action lawsuits.

Heat kills hybrid batteries

As mentioned, a temperate climate is the best for promoting long hybrid battery life, so a Honda Civic hybrid battery pack will last longer in Boston than it will in Dallas. The main enemy is heat and different hybrid automakers have different approaches to maintaining optimum temperature in the battery pack. Early Honda hybrid battery packs were air-cooled, however insufficiently, creating an artificially-induced hot climate.

The problem is that the chemical reactions in a nickel-metal hydride (NiMH) battery, as with all batteries, are dependent on temperature. Higher temperatures generally mean better reaction times, which explains why a warm battery delivers better power than a cold battery, but only to a certain limit. The old SLA (sealed lead acid) rule, “double the temperature, half the lifespan,” applies just as well to poorly-cooled hybrid batteries of NiMH chemistry. Higher temperatures can lead to “thermal-runaway,” that is, the chemical reactions race out of control, which leads to premature aging, electrolyte leakage, and possibly even fire.

AAA Hybrid Battery Repair’s holistic solution

If the IMA light has come on, typically reflecting a fault in the Honda Civic Hybrid IMA Battery system, one or more modules may be the root cause of the problem. Hybrid battery replacement may, indeed, solve the problem caused by a couple of overheated and compromised modules, but it is an expensive and possibly unnecessary step. Additionally, simple replacement, even with an updated controller and battery pack, doesn’t address the cooling problem, which puts the new battery pack in the same compromised position as the old one. What is needed is an overall approach, such as that offered by AAA Hybrid Battery Repair.

AAA Hybrid Battery Repair can determine which modules have failed, replacing just the failed modules. This is referred to as hybrid battery rebuilding or refurbishing, after which the hybrid battery goes into the conditioning stage. During hybrid battery conditioning, individual modules are carefully discharged and recharged, resulting in a well-balanced hybrid battery pack. Finally, upon installation, AAA Hybrid Battery Repair installs a fan kit which effectively reduces the IMA battery pack’s temperatures by between 12 °F and 20 °F, keeping the battery pack within safe limits. The entire process costs far less than full replacement and addresses the cooling problem, ensuring more years of reliable service, performance, and fuel economy.

How long does a Toyota Prius hybrid battery last?

How long does a Toyota Prius hybrid battery last?

Every part of a hybrid vehicle, just as in a conventional vehicle, is “living on borrowed time,” so to speak. Over months and miles, every part of the car eventually wears out, some parts faster than others. For example, tires and brakes can “last” anywhere from 20,000 to 80,000 miles, depending on climate and driver habit. Toyota engines, for example, are designed for at least a 250,000-mile lifespan. With proper maintenance, we’ve seen plenty of Toyotas with two- or three-times this mileage.

When it comes to hybrid vehicles, such as the Toyota Prius, most of the same rules apply, except that brake pads and the engine tend to last longer because they are used less than in conventional vehicles. In addition to the conventional vehicle components, however, there are also the hybrid vehicle components, including the electric motor generators, power control unit, and hybrid battery. Seeing as the Toyota Prius is one of the oldest hybrid vehicles on the road, it seems fit to ask, “How long does the hybrid battery last?”

Climate and driver habit

Most parts of the Toyota Prius hybrid vehicle are accessible for maintenance only by a technician, including tires, brakes, and engine. On the other hand, only driver habit has a direct effect on the health of the hybrid battery. While the driver doesn’t have direct access to the hybrid battery pack, his habits have the most impact on lifespan. Put simply, hybrid vehicles are best driven daily, with a good mix of stop and go traffic, and in a temperate climate.

Under the best circumstances, the Toyota Prius hybrid battery should perform well for five to seven years, mileage being much less of a consideration than in conventional vehicles. Given that the average American drives 11,500 miles-per-year, five to seven years on a Toyota Prius hybrid battery is somewhere between 60,000 and 80,000 miles, after which drivers may begin to experience declining performance or the fuel economy.

This doesn’t mean, however, that the hybrid battery will simply die at 81,000 miles, disabling the vehicle. Drivers may easily get up to twelve years and 200,000 miles before the hybrid controller determines hybrid battery performance is so far gone that it can’t use it anymore. A first-generation Toyota Prius’ poorly performing hybrid battery, for example, could be impacting fuel economy and performance in a big way. The 2001 Toyota Prius is rated at 42 mpg (miles per gallon) city, but could deliver as little as 30 mpg with a “spent” hybrid battery. Hybrid battery replacement may seem to be the best answer, but hybrid battery conditioning is an even better answer.

Hybrid battery conditioning

In the case of a first-generation Toyota Prius, hybrid battery replacement may cost as much as $5,000. Battery conditioning, however, may cost as little as $1,500. Battery conditioning uses the original hybrid battery pack, keeping hard-to-recycle rechargeable battery components from entering the waste stream. AAA Hybrid Battery Repair recommends hybrid battery conditioning every 60,000 to 80,000 miles before the hybrid battery pack begins to impact fuel economy or performance, but how long does this last?

The Toyota Prius’ nickel-metal hydride (NiMH) battery is very resilient, but it does have a limited lifespan in respect to its balance. The hybrid battery pack is composed of between 168 to 240 individual cells, assembled in 28 to 40 modules, depending on the year, each of which ages differently. Over time, capacity and performance can vary greatly between modules, and a hybrid battery can only perform as well as its weakest module. Hybrid battery conditioning restores the whole pack to a well-balanced state, restoring as much as 95% of factory performance, and can last as long as the original new battery, delivering peak performance and fuel economy for an additional five to seven years.

What other maintenance should HEV owners be aware of?

The HEV high voltage system is comprised of four major sub-systems.

These sub-systems are the Battery Pack, Electric Transmission (that contains a drive motor and generator unit – MGU), Power Inverter, and dc-dc Converter. Some HEV systems also contain an Electric Air Conditioning Compressor.

Electric Transmission and/or Motor Generator Unit (MGU) Testing

During the life of an HEV, the 3-Phase MGU units (much like an engine system) age and eventually fail. From the time an MGU system is new until failure there is the “in-between stage” of stator winding and rotor aging. MGU aging or its other failure modes can cause the vehicle to surge, shudder, or intermittently cause a driveability symptom similar to an engine misfire. MGU’s can also exhibit audible noises, or cause the power inverter system to run at elevated temperatures. The MGU SOH should be tested at regularly scheduled maintenance intervals to trend/track its condition (aging), or test it if the vehicle has a customer driveability concern/complaint. It is extremely important to test the MGU system for SOH because, the electric drive motor is responsible for launching and propelling the vehicle during the first 20 – 30 mph of an acceleration, and the generator is responsible for providing the electric drive motor and battery pack electrical energy during normal vehicle operation. Most MGU performance problems will not cause the MIL to illuminate to inform the operator that there is a problem. Typically, the MIL will only be triggered when there are more catastrophic (chronic) problems. The MIL will typically not be triggered for intermittent MGU malfunctions.

Power Inverter and Control System Testing

To power the MGU system, the 3-Phase Power Inverter system receives direct current (DC) electrical energy from the Battery Pack system and inverts (changes) the DC energy to alternating current (AC) 3-Phase electrical energy. It then transfers the 3-Phase electrical energy to the MGU system to electrically propel the vehicle, operate with the vehicle engine to blend motive power to the wheels, and recharge the Battery Pack. When the Power Inverter and Control System are operating properly it provides smooth electrical energy to the MGU to electrically propel and move the vehicle. However, when the Power Inverter system malfunctions (either because of abnormal external inputs to its control systems or internal electronic malfunctions) it can cause the vehicle to perform poorly resulting in a sub-standard driveability experience for the vehicle operator. Therefore, testing the Power Inverter system SOH should be tested at regularly scheduled maintenance intervals to trend/track its operating condition or test it if the vehicle has a customer driveability concern/complaint. Most Power Inverter performance problems will not cause the MIL to illuminate to inform the operator that there is a problem. Typically, the MIL will only be triggered when there are more catastrophic (chronic) problems. The MIL will typically not be triggered for intermittent Power Inverter malfunctions.

dc-dc Converter System Testing

HEVs do not contain a traditional belt-driven “alternator” as part of the electrical system. The alternator (generator) provides electrical power to operate vehicle lighting, door locks, power windows, engine electrical systems, etc. The dc-dc Converter replaces the alternator to provide electrical power for operating all of the vehicle electrical systems. The dc-dc Converter is a solid-state electrical system receives its electrical energy from the high voltage battery pack and converts (reduces) this high voltage to low voltage so that the vehicle can use this electrical energy to power the low voltage vehicle systems. The dc-dc Converter should be tested at a regularly scheduled maintenance interval for proper electrical power output capability and to ensure that its output energy is “quiet” (i.e., poorly filtered high-frequency signals are not causing noises in the radio or other audible noises). The dc-dc Converter should be checked if proper 12-volt vehicle battery charging cannot be maintained, if the vehicle lighting is lacking brightness (lights are dim), or if blower motor speeds seem to be operating slower, etc. Proper dc-dc Converter operation is critical to the operation of all vehicle electrical systems, including the HEV system.

Other Maintenance Items

If the Power Electronics cooling system for the Power Inverter, dc-dc Converter, and/or Electric Transmission is a liquid system (i.e., a system much like the engine cooling system) ensure that it is maintained to prevent the power electronics from overheating. Maintain proper tire inflation in the tires. Many HEVs use “low rolling resistance” tires to enhance fuel economy and proper tire inflation pressure is critical to maintaining high fuel economy. Have your service center check the orange-colored high voltage cables that are routed under the vehicle (exposed to road debris) for any cuts, tears, punctures, etc., permitting water intrusion into the cable. Water intrusion can cause various abnormal electrical operating conditions, including the vehicle, not cranking/starting. Road debris not only can also cut through the outer sheath of the high voltage cable but, it can also cut through the cable shield and into the copper core. This can cause abnormal vehicle operation but, it can result in safety concerns. The service center technician can easily repair the cable. The cool/cold air from the vehicle air conditioning (A/C) system, on many vehicles, is used to cool the high voltage battery pack. If the A/C system is not performing or not operational it can cause the battery pack to operate at elevated temperatures. If the battery pack operates at elevated temperatures, the hybrid controller can command the system to operate in a “reduced performance” mode (i.e., vehicle has sluggish performance) to reduce demand on the battery pack so it operates at a cooler temperature

What are the Pros and Cons of Hybrid Battery Replacement and Conditioning?

There are numerous Pros and Cons when addressing the issue of battery pack replacement or Conditioning. When considering installing a used battery pack, there is always an issue of not knowing the condition of the unit. Therefore, there is significant risk in purchasing used products. Rebuilt units are always a consideration because there is an expectation that the battery pack has been tested and is sold with a warranty. However, the reputation of the rebuilder needs to be considered before utilizing a rebuilt unit. There are numerous HEV battery pack rebuilders that are using processes, procedures, and methods that are not grounded in industry testing standards. Additionally, many rebuilders do not provide battery data with the unit for the purposes of documenting its performance. Rebuilt battery units are typically ½ the cost (and ½ the warranty period) of a new unit. New units can provide excellent performance with a good warranty from a qualified manufacturer but, this always is coupled with significant cost. Conditioning provides a solid solution for customer. When performed by a trained professional, Conditioned battery packs can provide excellent performance with minimal risk for ongoing electric propulsion performance. Conditioning is approximately one-half the cost of a rebuilt unit that is usually accompanied by a 1 year to 18 month warranty period.

New vs. Conditioned Batteries: Which is better?

A New battery contains all new (or qualified as new) components including battery modules, relays, wiring, electronic controller, etc. A Conditioned battery pack utilizes the existing battery components.

How long will Hybrid Battery Conditioning last?

Conditioning battery packs provides an extremely positive impact to the environment. By Conditioning an HEV battery pack in lieu of replacement, far fewer battery packs will be produced or placed into the salvage stream. By reducing the number of battery packs in the salvage stream this will reduce the volume of metallic and non-metallic materials in the recycling and refuse streams. Conditioning battery packs results in reusing existing resources and reducing the need for manufacturing additional battery pack materials.

Should I have my Battery Conditioned or Replaced?

Conditioning – Most hybrid electric vehicles (HEV) utilize Nickel Metal Hydride (NiMH) battery technology and can lose much of its capacity over time. Conditioning a battery pack means that no components are replaced. After removal from the vehicle the battery pack is initially tested for Power and Energy to determine its current state-of-health (SOH). After initial testing, the battery pack is “cycled” (using a controlled charging and discharging process) to increase the capacity of the modules.

The capacity of most NiMH battery modules can be increased to approximately 92-95% of a new battery module by cycling. If any of the battery modules fail to provide proper Power or Energy, a simple replacement of the individual non-performing battery modules can be accomplished to increase the performance of the battery pack. Most battery pack performance problems will not cause the Malfunction Indicator Lamp (MIL) to illuminate to inform the operator that there is a problem. Typically, the MIL will only be triggered when there are more catastrophic (chronic) problems. If most battery problems are caught before the MIL is triggered, it can usually be Conditioned back to good health. The MIL will typically not be triggered for intermittent or mediocre battery pack operation/malfunctions.

Battery Pack Replacement – is also another battery pack service option to the customer, albeit more expensive than conditioning. Replacement of the battery pack can be accomplished in three different levels of service. The three levels of battery replacement are installing a used, rebuilt, or new battery pack.