You probably already know that a hybrid uses a gas engine combined with a battery and electric motor system for increased fuel efficiency and reduced emissions. That’s cool, but how long do hybrid batteries last? Some owners think the battery will last forever, while others call it the car’s kryptonite. The truth probably lies somewhere in between.
How long do hybrid car batteries last?
Questions about hybrid battery life are usually several different questions wrapped in one. First, if you’re buying new, or your used hybrid is only a couple of years old, you’re probably wondering about the hybrid battery warranty. For most manufacturers, hybrid system coverage lasts eight years or 100,000 miles, whichever comes first. For 2020, Toyota upped the ante by increasing their coverage to 10 years, or 150,000 miles. The warranty gives us a good general ballpark figure for battery life, as the manufacturer will ensure most of their batteries will last beyond the warranty period.
After the warranty runs out, hybrid battery life gets confusing. While auto manufacturers like to communicate in broad generalities, they usually don’t hold up well in our personal lives. So there is no specific mileage or age to avoid when shopping for a used hybrid. It could fail at 50,000 miles or cruise past 300,000. When called directly on this subject, a Toyota dealership service advisor said he usually sees hybrid battery failures after 10 years and starting at around 180,000 miles. That’s decent, but then there are news articles about hybrid taxis and rideshare cars running well past a half-million miles. What gives?
“It depends on the technology,” said Peter Neilson, a former Toyota technician and consultant with 16 years of experience in hybrids. “The majority of hybrids on the road today are using nickel-metal hydride (Ni-MH) batteries. With Ni-MH batteries, if the car is in regular use, they’re putting on the average miles per year, you’re going to see about 10 to 15 years of use out of that battery.”
What does this mean for the typical driver? The average American drives 13,500 miles annually, so a new hybrid should last 12 to 14 years before the battery quits. The average age of a car on the road was 12 years in 2020, meaning a hybrid battery should last the life of the vehicle. However, hybrid battery life is not all about miles.
What determines hybrid battery life?
Just like the useful lifetime of any other battery, hybrid car battery life depends on several factors. Some of these you can’t do anything about, but others are within your control. These factors can help you decide if that used hybrid you’re eye-balling is a good buy or not.
Obviously, this is a big factor. The higher the mileage, the less battery life remains. This is true of a regular 12V battery, too, because mileage equates to run-time. While battery internals don’t operate like those inside an engine, think of them as a lightbulb. A lightbulb in your kitchen turned on and off 20 times a day won’t last nearly as long as a utility room light that sees action twice a week. However, low mileage can also be a warning sign.
“Lack of use is a big thing that determines battery life,” said Neilson. “The thing is, with Ni-MH, if it just sits, it kinda goes stale. That’s why there are Priuses out there with 300,000 plus miles on them, on the original battery. That’s because they’re getting exercised like crazy, so they don’t fall to that battery memory deformation.”
Ever notice how your phone’s battery life takes a hit after two years? That isn’t just the manufacturer building in planned obsolescence, it’s a real problem with batteries as they age. The battery that used to last all day now lasts only two hours, a problem known as “capacity fade.” This happens with all batteries, including modern li-ion hybrid and EV batteries. Capacity fade happens due to use, so like mileage above, simply using the hybrid will degrade the battery over time.
Few people vacation to Nome, Alaska, in winter, or enjoy Las Vegas weather in August. Still, people live in both places year-round, and while you might have heard that temperature decreases EV range, extreme temperatures can also damage your batteries. Manufacturers understand this, and the Prius has a dedicated air system to blow cool air at the battery, while Tesla goes all-out with complex liquid cooling. However, there’s only so much these systems can do if the temps are -40 or 120 degrees. You’ll complain, and so will your hybrid battery.
A body at rest will remain at rest, while a body in motion stays in motion. Isaac Newton provided some useful advice about cars here. Cars, and especially their batteries, wish to be used. Leave your car sitting for a month, and you probably won’t be able to start it. Leaving the battery in this low charge state will permanently damage it. Just as racking up 100,000 miles a year will quickly wear out your tires, driving only 100 miles per year will also quickly damage the battery and other components.
Ever pick up your phone while it’s on a fast charger? It’s noticeably warm. As you read above, heat kills batteries. Battery use generates heat, but so does charging. Buyers demand quick charging times while away from home, with 250 kW to 350 kW generally available to the public. This increased power causes increased heat through resistance, which in turn causes battery degradation over time. Granted, this tip applies only to plug-in hybrids, but keep the charging low and slow.
Why do hybrid car batteries fail?
An engine can wear out when the piston rings fail, making the engine lose compression to where the proper combustion process doesn’t take place. What about hybrid batteries? Without moving parts, it would seem like they could last forever.
“I’m very familiar with the reconditioning process after failure,” said Neilson. “But understanding why the batteries fail was a big eye-opener to me.”
Neilson explains dendrites as electron inhibitors that build up like a stalagmite inside the battery with age and use. Electrons can’t pass through the dendrite, so it disrupts battery performance.
“If we get enough dendrite formation in a battery cell or module, the electrons will try to flow, but they can’t, so they’ll basically explode the battery, because they have nowhere else to go except out.”
Hybrid batteries are actually made of hundreds of little cells, essentially many small batteries making up dozens of larger modules which then make up the big battery. Due to slight variances during construction, hybrid cells will always have slightly different capacities. When the difference goes beyond a few percent, the cells and modules are unbalanced and the overall battery capacity is reduced. This problem gets worse with age and use, lowering the capacity of the battery.
“What’s really tricky about this is if you replace just a module, it can actually upset the balance of your battery and cause the battery to go into failure mode sooner,” Neilson said. Imagine, for example, a sports team of 40 year olds suddenly adding a 20 year old mid-season. The younger player initially helps the overall performance, but eventually, his frustration with his older teammates’ limitations makes them worse off than they were before. In batteries, older modules simply can’t compete, so it upsets the balance and sends a trouble code.
How to tell when to replace a hybrid battery
Curious if your battery is going bad? Don’t worry; you’ll know. The Toyota Prius, for instance, puts up a big red “triangle of death” on the dash gauges, along with a check-engine light, maintenance-required warning and multiple annoying beeps. Here are some warning signs to look for to try and avoid getting to that point:
Manufacturers list hybrid specs using “total system horsepower” of the gas engine and electric motor(s) combined. You are also used to the performance of this total package. As a battery starts to fail with limited capacity, the reduced storage of the battery means it drains easily, so it leans more on the small gas engine for power. Without the battery powering the electric motor, you’ll feel the lack of torque around town. The vehicle has sluggish power on acceleration, and you find yourself using more throttle to maintain speed.
Reduced fuel economy
Since you have less power in a hybrid with a failing battery, you’re pressing the throttle further or having to hold it down longer to get up to speed. This extra use of the gas engine directly relates to increased gas usage. Without the ability to cruise in electric mode, the hybrid keeps the gas engine on, lowering your MPG and draining your wallet.
Twitchy battery status
Let’s say that when you parked your hybrid last night, you noticed the battery was mostly full. Yet, when you went to start it the next morning, the battery status showed nearly empty. What’s going on here? Draining overnight is a common warning sign of an aging hybrid battery.
“It’s called ‘negative recalibration,’” said Neilson, explaining that the instruments are reading the false full status from the surface charge of the battery, and not its actual status.
How to prolong hybrid car battery life
Odds are, your hybrid battery life will end around the same time the vehicle sees the end of its service life. Hybrid batteries are built well and should last you several years. However, there are drivers that are heavy on the throttle, drive in extremely hot and cold temps and run their cars to the limit. That will limit the battery life. Here’s how to try and avoid doing that:
Service the car on-schedule
There’s a handy book that comes with all vehicles that most drivers ignore and leave in the glove compartment. Don’t be that person; read your owner’s manual. In the maintenance section, you will find the manufacturer’s recommendations for service, including hybrid components. This won’t be very much maintenance, or very often, but it can prove critical to hybrid longevity. For example, the Ford Escape hybrid needs an air filter for the battery every 40,000 miles, and you have to change out the inverter fluid in the Toyota Prius at 100,000 miles. Proper maintenance will help the battery, and the rest of the car, live as long as possible.
Charge plug-ins correctly
Again, look through that handy owner’s manual. There are several kinds of charging systems and speeds available, but you want to use what the manufacturer recommends. If your owner’s manual says to only use Level 1 or 2 charging, then going with faster charging causes excess heat, which could damage the battery, reduce its capacity, or even cause a fire. Trickle charging helps your standard 12V battery live longer, and slower charging seems to work best for plug-in hybrids and EVs too.
Avoid extreme temperatures
Remember, heat is the enemy. Keep your hybrid battery at a reasonable temperature with a climate-controlled garage. That’s not always an option, but even an insulated garage is better than getting directly blasted by the sun’s heat in summer. Park in a parking garage or shady parking spot when you can, and use a sunshade or heat reflective tint on the windows to keep the interior cooler.
Regularly screen the battery
Curious about the health of your hybrid battery? While engine health can be checked with a compression test or oil analysis, you can get similar information on battery health through a stress test. This is usually performed by a dealership service center or mechanic using professional diagnostic tools, but it provides a clear look at your battery health. There are aftermarket tools that let you DIY analyze the battery, but they aren’t cheap. These tests can show you which cells or modules have deteriorated, which opens up the more affordable option of just replacing the individual modules.
“Reconditioning helps with battery balance,” said Neilson. Battery reconditioning systems vary widely in complexity, user-friendliness and price. “There are a lot of different products out there,” according to Neilson, but they all perform the same function—correctly discharging and recharging the hybrid battery to prevent dendrite formation, which maximizes battery capacity.
“If you want to keep your car for another 15 years, buy a brand-new battery and the car will perform perfectly. Do periodic reconditioning, and you’ll keep it for the rest of your life," Neilson said.