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I really like hybrid cars e.g. Toyota Prius ... but I would like to drive them without their battery so that I can drive them only on petrol and don't have to worry about battery maintenance / replacement. Is it possible that I remove the battery from Toyota Prius and drive it like a regular non-hybrid car?

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  • Why bother? "Because I have lots of experience with car batteries and they're short-lived and only last 4-6 years". False, those are not your father's batteries. In the year 1900, EVs were built with 40-year nickel-iron (Edison) batteries, or far cheaper lead-acids that last an appalling 4 years. It turns out lead-acid is good at high surge currents (starting gas engines) and Edisons weren't. That's why lead won the "war of the batteries" back then. But it's certainly not a good battery, and no one uses them for EVs/hybrids. Dec 2, 2021 at 19:40

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No, this is not possible.

The high-voltage (HV) battery is used to start the engine. Remove this battery, and you soon find yourself unable to start the engine. The engine is started by motor-generators (MGs) operating on the HV battery, not a conventional starter motor operating on 12V auxiliary battery.

Also, the simulated Atkinson cycle engine would totally suck without the electric boost from the HV battery. So if you somehow managed to install a traditional starter motor to a Prius (which ain't easy), you wouldn't like the car at all.

You are worrying about the wrong things. The battery is reasonably durable. Consumer Reports has tested two about 10 year old Prius cars, one had only few thousand miles and the other a lot more. Both had good fuel economy even with 10 years and for the other car, lots of miles. If you find yourself with a bad battery, a junkyard battery can probably be found and installed for less than $1000.

In case you have a bad battery (which can happen, as evidenced by a comment here: Toyota Auris Hybrid sometimes is reluctant to enter READY mode), in most areas Toyota has a good warranty for the battery. In Finland, the warranty is 10 years or 350 000 km.

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It's not possible - and it's probably not what you want anyway. My first Prius lasted over 350,000 miles (570,000 km) without any battery maintenance whatsoever. If there were a way to run without the battery, you would be making the petrol engine do much more work, increasing your maintenance cost.

Toyota HSD is careful to avoid over-charging or depletion of the HV battery (the battery gauge on the dash actually ranges from 40% to 80%, rather than the 0-100% that it looks like), so battery life is much better than devices like cameras that you tend to fully discharge.

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This is due to your misperception of lead-acid batteries

Most people think "all batteries are alike". They've never been educated on the subject.

Traditional car batteries are lead-acid. They are extremely poor batteries. They don't last. But they have 2 useful traits:

  • they're unusually good at surge currents
  • they're cheap.

By contrast, consider the EV market at the end of the 19th century, when automobiles were a toy of the rich. Gasoline engines were hand-crank, and so dirty and fidgety that you had a driver-mechanic actually operate the vehicle. Yet a respectable lord or lady could operate an EV themselves, allowing them to go places that perhaps they didn't want their driver/mechanic discussing with the servants. In that day, you had two battery options: The magnificent nickel-iron "Edison" cell, which lasts 40 years and excels at deep-cycling... or the low-performance but dirt cheap lead-acid battery, which is bad at deep-cycling but so cheap no one cares.

Of course, discerning buyers went for the Edison battery, and many in museums still work. In fact, I maintain an Edison battery for a museum, which was from the 1960s.

Gas engines would never take off until the electric starter came along. Automakers now looked for a battery that would crank over gas/Diesel engines, yet would have the lowest total life-cycle cost (for 10-15 year vehicle life). This is where lead-acid's one good trick - high surge current - brought it to the fore.

When gas engines became king, lead-acid became king.

Because from about 1920 to 2000, except for submarines, the only purpose anyone ever cared about large batteries was whether they could start an engine. Lead-acid was so dominant that even submarines used lead-acid even though they endangered their crews! (only last year, the first lithium submarine launched.)

Lead-acid batteries, being cheap, were considered "wear items" like brake pads or air fresheners, to be changed frequently. They put the battery right on top where it comes out with 2 screws.

Obviously, that won't do for an EV.

With EVs, they revisited the great, old tech

They started at Edison (nickel-iron) batteries, which were the gold-standard for electric vehicles, being great at longevity, deep cycling and overall energy capacity.

That morphed into nickel-cadmium, then nickel-metal-hydride, which were indeed used on early hybrids, and performed well.

When battery developers started exploring the lithium line, they knew that Edison-family batteries "set the high water mark" they would have to beat. So lithium designers aimed for long life on large, automotive-tier batteries... and they were able to hit the mark.

Further, they were able to hit the mark across the board. For instance, Tesla batteries are large assemblies of thousands of "18650" type laptop batteries. (laptops don't do as well, because laptop batteries are wired in series, so the weakest cell hurts the pack. Tesla packs have ~100 in parallel, so a single failed cell has little effect.)

As Toby discusses, another lithium trick is to manage the charge range. While the battery is electrically able to go from 0% to 100%, it greatly extends battery life to avoid the bottom and top few percent of charge. So they program the car's firmware to avoid that, and market the battery as having lower amp-hours than it actually does. This is how, for instance, whenever a mass evacuation is called, Tesla does a software "push" to unlock the full capacity of people's batteries.

Take the Chevy Volt, which is a very strong hybrid that runs entirely electric for weeks at a time, for many owners (engines and fuel deteriorating from disuse is a problem designers had to figure out!) The overall capacity of that battery really matters to its job.

Contrast that with "weak hybrids" where the battery is just there for peak shaving -- so you can accelerate on a freeway ramp, without having to drag around a 250 horsepower V6 that you only use for that. If that battery were to fade, well, you lope up the freeway on-ramp a bit slower, is all.

The used aftermarket has you covered, anyway

The aftermarket is flush with battery rebuilders, who are pulling battery packs from wrecks, load-testing cell by cell, identifying dead cells and removing them. A lot of hobbyists do this too with batteries from old laptops and medical equipment, and it works - it produces reliable battery packs.

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