Here is my thinking, assume you have 2 electric cars. One has a 200 mile range, one has a 500 mile range.
The one with the 500 mile range will cost more for the batteries. But you will not recharge the batteries as much. If you assume you recharge them after hitting 50%, that means you recharge every 100 and 250 miles respectively (I don’t think it is good to drive until the batteries are near dead, but I don’t know). So if you put 50,000 miles on a car, with the 200 mile battery pack you have recharged it 500 times, with the 500 mile battery pack you have only recharged it 200 times.
Would the battery pack from the 500 mile car last longer, and as a result make the battery pack last for twice as long? ie, would you have to replace the batteries in the 200 mile car at 100k miles, but not have to replace the batteries in the 500 mile car until 250,000 miles?
Or does the math not work like that? If it were that easy, why wouldn’t car manufacturers put bigger batteries in all the cars?
Basically, is there a tradeoff between the battery capacity, how many times you recharge it, and how long the battery lasts before needing to be replaced?
The Volt has a 16kwh battery and that is warrantied until 100,000 miles. Even at that point the battery should still work, but capacity will be a bit lower.
Bigger batteries also add weight. So doubling the number of batteries won’t double the range. There’s a sweet spot that balances extra power with extra weight beyond which you see diminishing returns.
For one thing, the weight of the larger batteries is significant. Just carrying all that extra weight around means that the car will use a lot more energy to go from point A to point B.
Car batteries also use variants of lithium ion type chemistries, IIRC. Lithium ion batteries are lightweight and have an excellent energy density for their size, which makes them great for cars (and laptops and cell phones and all kinds of things). Lithium ion batteries have problems, though. For one thing, they start dying from the moment they are made, and there’s not much that you can do about it. The formulas they use in cars is different than what they use in your typical laptop or cell phone battery, but the aging effect is still there. They just use formulas that are better with respect to aging that what you find in small consumer electronics.
So you can’t just double the capacity and expect it to last twice as long. The battery will die much sooner than that just from internal aging. Whether you drive the car 25,000 miles or 250,000 miles in ten years, the battery is going to be pretty well shot at the end of those ten years either way.
Yes they cost more, but they also will not need to be replaced as often. I remember a few years ago reading about how batteries needed to be replaced after X miles.
However I do not know if that is still the case. If a battery pack will last 200,000 miles, it probably won’t need to be replaced since most cars do not make it much past 200k.
Your correct running lead acid batteries, they should last longer if only cycled to fifty percent.
The advantage of lithium iron phosphate batteries is they can be cycled hard plus overcharged somewhat without damage.
Similarly with lithium ion batteries you can cycle them hard, however not a good idea to overcharge.
Using expensive lithium chemistry batteries and only cycling fifty percent is just not a scenario you’d consider, it’s wasting the benefits they provide over lead acid cells.
It will surely depend on what you intend to use the car for. In the UK, a typical commute distance is between 10 and 15 miles, so a small car that can do 50 miles between charges would be perfectly adequate. I assume that the typical American who drives to work, has further to go, but the principle is the same.
JC on Top Gear, made much fun of electric cars, because they ran out of juice after a couple of hundred miles. This was ‘good’ TV but bears no relationship to real life use.
So if you can drain lithium ion batteries to near zero, how many times can you recharge them? I recharge my phone every day and my last phone lasted 2 years before I replaced the battery, that is like 700 recharges. I’m guessing electric cars have batteries that last longer.
The problem is that the average driver is also going to be making a few long trips a year: on vacation, going home to the family for Christmas… So what do you do about these longer trips? (although a multi-car family could have one car as a short distance commuter)
Rent a car. And if that’s such an unpalatable option, then electric probably isn’t for you. That doesn’t mean it’s not still a good fit for a lot of other people.
All other things equal, the math works exactly like that.
Battery life has two components, cycle life and calendar life. For daily deep cycling batteries (like the ones in an electric car) the most significant factor by far is cycle life. A primary specification for these batteries is for how many cycles they will last.
So if you put the same type of battery in your example cars, and drive them daily, the larger one will last longer exactly like you calculated.
OTOH, to illustrate calendar life: if you drove each car just once a year, they would last about equally long.
The practical situation is of course more complicated. Batteries are not created equal. There is great variation (and engineering trade-offs) in cycle life and other properties of batteries. So you could also say that a car manufacturer that puts in a big battery can use a type having lower cycle life to reach the same mileage.
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For one thing, they start dying from the moment they are made, and there’s not much that you can do about it.
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I would like to add that actually there’s a great deal apart from formula that “you” can do about it, where “you” are either the car manufacturer or the customer. For a given battery, temperature greatly affects both the cycle life and calendar life of a battery. A car manufacturer who puts in good temperature control mechanisms will significantly extend the life of the battery in hot climates. The big user controllable factor is State of Charge, i.e. how full you keep the battery and how far you discharge it. In the OP’s example, if you keeps one of the cars plugged into the charger all the time, and the charger is not properly designed to take care of the battery, that battery will wear out much faster.
So the answer is that the math does not work like that on many levels … plus there are a few major unknowns.
Limiting factors for batteries include cost, volume, and weight.
Degradation varies depending upon particular battery chemistry but is not a simple function of number of cycles or depth of discharge.
Life expectency of current batteries in real world applications is still unclear. The Nissan Leaf battery (which should age fast as they lack active thermal management and are only air-cooled) has so far had a failure rate of only 3 out of 35,000 sold.
Given that charging systems and battery management software prevents overcharging and too deep of discharge some believe that current actively thermally managed batteries should be able to last the life of the vehicle as they are.
Well, we’ll see.
Last unknown is that we do not know what future battery costs will be. Odds are less cost per kWh capacity. Better to invest in what you need now and IF it needs to be replaced then get replacement capacity for less cost or take advantage of possibly improved greater capacity per unit volume, weight, and/or dollar.
Slightly down that page, you can see one particular result where a certain kind of Lithium Ion battery (though not the kind typically user in phones) lasted 1200 cycles when “completely” discharged but 12000 cycles when discharged by only 20%.
How soon until a new “Breakthrough” battery chemistry comes along?
Lithium-Ion is a huge improvement over lead-acid - so now an “electric car” can be much more like a car than a golf cart - which is what “electric car’” meant 20 years ago.
I have to believe a few thousand chemists and engineers are working on the “Next Gen” storage battery or a way to power vehicles without using storage batteries.
Any informed guesses as to when such a breakthrough will come?
Is Tesla dragging its feet on the “Giga Factory” so as to be ready to produce a new chemistry?
Volt owner here. Most modern electric cars use software and fans to regulate the temperature and charge state of the battery to optimal levels. This greatly increases their lifespan. Every year battery costs decrease and energy density increases. Am I stressed over the failure of my car’s battery? Not in the slightest. I’ve own many different vehicles and I’ve had to do several repairs on my old ICE cars in excess of $3000. The battery is warranted to 100k, so if I have to replace it for $2000 at that point, I still have saved on a lifetime of regular maintenance (oil changes, brakes, etc.) that it is basically a wash.
I keep watch, for purposes of investing, and so far I’ve only seen one new type of battery getting moved from the lab to the production line (Oak Ridge Labs -> Solid Power), though the production line is still under development.
I believe that Solid Power is going to be targeting military and space, rather than consumer electronics. But, assuming the batteries are sufficiently user friendly and if the military buys enough of them, that should allow them to drop the price and sell on the general market.
Other than that, a few companies have mumbled about being in development on some new tech, but none of them have given any particular date for release. Sony has said 2020, but they’re sounding pretty wishy-washy on it.
Plausibly, in 5 years we might see next generation batteries hit the market at a slightly-too-high price. But I’d give at least 8-10 before they’re standard issue in your average electric car. But that’s probably a minimum.
But with at least one technology going to production, I do think that the minimum timescale is fairly plausible to be hit. (IMHO)
And just to pile on, there’s several cars now like the Volt (or my own Hyundai Sonata PHEV) that are basically electric cars with a “gas backup.” I can drive it any distance I want (at the cost of frequent fill ups since it’s got a smallish gas tank), but I put gas in it on average every six weeks, and it’s given me 138 MPG average since I bought it 4K miles ago, for about $50/month extra on my electric bill.
Aside from the hijack, the battery pack is warranted for the life of the vehicle to the first owner (why first owner only? no idea), but the manual says that slow decreases in the life of the battery are a result of time rather than distance/charges (and should not be significant).
Is $2000 the cost to replace it? I think batteries are at $160 a kwh, and the Volt has a 16 kwh battery. Plus you add in labor, maybe 2-3k or so is a good estimate. But assuming you do 1/4 of your driving on battery, that means every 140 miles you totally drain the battery, so by 100k miles you have drained and recharged the battery 714 times. Which again, seeing how cell phone batteries can be drained and recharged daily for 2 years or more, is not bad.
However for a car like the Tesla with an 85kwh battery it’ll cost more.
Supposedly prices will decline to $100 a kwh by early the next decade but who knows when a totally new tech will come along. Batteries that are $25 a kwh would be nice seeing how every kwh is about 3 miles in range.