Different battery designs and chemistries are appropriate for different applications. I don't care about how much a battery weighs if it never moves, for example.

The powerwall use case will only grow when people get solar panels and when rural areas in countries lacking power infrastructure eletrify. But while that use case doesn't care as much about weight, bulk, charge rate and % capacity as car batteries, in return they are very sensitive to cost and the market will (depending on how cheaply recycling can be done) likely be filled with used car-batteries with degraded capacity.

If you invent a battery that is 2x as large and heavy as current vehicle batteries but half the cost, then you might think you would be able to sell them for stationary storage, but you are then competing with the price of second hand vehicle batteries which may well be half price already.

One drawback of using lots of lithium batteries in your home is that they might experience thermal runaway and burn your house down. Not having to worry about that should have some additional value.

Most new solar installations now use LiFePO4 which apparently is much safer on that runaway side...

That's good, but is that what's used in "used car-batteries with degraded capacity"?

Used car batteries are conventional unsealed, lead-acid batteries. Lithium-iron-phosphate (aka LiFePO4, LFP) batteries is a different battery chemistry altogether. It is touted as the answer to a deep-cycle, lithium-based electrical storage that the traditional lead acid batteries occupy.

I think they mean used EV batteries - EV batteries that are at the end of their useful life in cars.

That makes more sense.

Also way better cycle life, but the density is slightly lower.

I'm of two minds on this.

On the one hand, you're right that for different applications having different metrics can be acceptable. Sure, a battery for your home that never moves can be heavy and large and that's okay.

But then you have to consider the economics of production. How many of those batteries will you make? What will the factory for them cost to build? And what would it cost instead to just make a bunch more Li-Ion batteries at the existing factory instead?

Your logic makes sense if there is only one battery factory. But there are and will be many.

Economies of scale still apply with multiple factories because you need someone to design and build the equipment used at each of them.

Where do flow batteries (fuel cells) fit in those calculations?

Some of the more exotic battery designs are things like "rust powder held in a silo at a certain temperature" which presumably can be assembled on-site. It seems to me overly reductive to assume that stationary batteries will be "just mobile batteries but heavier".

True (within limits), but the largest use of batteries is batteries that move. Utility scale power storage is the only significant use of battery that doesn't move. (there are others, but they are not probably large enough to develop a battery for, and so will be stuck with whatever they can get from the other markets)

Yes, but stationary energy storage is itself a large use case.

There are also different performance profiles within EVs, where different tradeoffs might make sense. Though, like you, I'm somewhat skeptical that any non-lithium chemistries will break through in that space.

There is already a car which uses two battery technologies in parallel.

This would also allow you to configure or offer cars optimized for the climate they are being used.

I personally also see those news more in 'im 5-10 years' we will have something much better than now.

Which car? You cannot drop something like this without a source

I’m sure this is not what the poster meant, but in fact most EVs and hybrids use multiple battery technologies in parallel. For example, a Chevy Bolt has a lithium ion battery to power the drivetrain and a conventional lead-acid battery for the accessories. My old Prius had a NiMH battery for the drivetrain and a lead-acid battery for accessories.

> For example, a Chevy Bolt has a lithium ion battery to power the drivetrain and a conventional lead-acid battery for the accessories.

This seems like an odd choice - unless you already bought a supply of lead-acid batteries for the next 50 years or so.

I've read about a car using supercapacitors in the regenerative brakes to capture energy at high current and, then let it trickle back into the main batteries (or drivetrain) at levels that won't damage it.

This is a classic, it isn’t broken don’t fix it situation.

Many laptops had both a lithium ion battery and a watch battery used to keep the bios and an internal clock running after the battery died. https://www.makeuseof.com/tag/why-does-my-motherboard-have-a...

That was a bit of a necessity. Users wouldn’t want their clock to reset when they swapped batteries, and you couldn’t be sure the machine was connected to a time server to set the time at boot.

The 12v lane is ubiquitous, and standardized. Supercaps are inefficient when it comes to storage per weight and volume, discharge rate too.

Both lead acid and supercaps are not even remotely comparable to the main liion battery, they're suppliments, and not interesting ones

The supercaps aren't for long-term storage - just long enough to allow the extra juice to flow back to the batteries. Racing cars sometimes do that with flywheels.

As for 12V, all one needs is a regulator. Unless you have a long-term supply contract (that, I bet, won't be renewed for too long), a lead-acid battery is just dead weight.

It could be great if you were a car manufacturer that already had an existing, very large supply chain for lights, dashboard, powered window motors, and other accessories, that were already 12 volt.

But unless you have a already contracted lifetime supply of lead-acid batteries, a buck converter is much cheaper, and lighter.

Tesla switched from lead-acid to 12V lithium ion their S and X models in 2021. James May had some issues with his Tesla when the 12V battery went flat.

https://insideevs.com/news/546087/tesla-liion-12v-auxiliary-...

https://youtu.be/NsKwMryKqRE

Tesla is also switching to 48V for the accessories.

This was the best news I heard at Tesla investor day. It should simplify and cut the cost of the in-cabin wiring.

When Sandy Munro interviewed Elon Musk a couple of years ago he said "Why are you still using 12v stuff in the cabin?"

Musk's answer was that the automotive supply chain was entirely geared around 12v equipment and they had to take advantage of that to get to market quickly.

I'm glad those days are almost over.

Isn’t there a whole trucking supply chain geared around 24 Volts?

All it'd take is a middle terminal in a 24V battery to make it a 12/24V one.

That would run the risk of unbalanced batteries. I had a small truck years ago, and everything was 24V as far as I recall.

A lead acid battery is just a holdover from the way every car used to have one for the accessories, and unless you want to redesign all the accessories, it's easier to have a 12v-14v circuit just for that.

And before you say "oh, but they could just use a voltage converter from the high voltage battery", they need to consider that some accessories use hundreds of amps briefly (eg. the power steering - that makes for an expensive voltage converter), and the car still needs to operate lights and stuff while the high voltage battery is offline (eg. after an isolation fault).

For all of the above reasons, the lead acid battery is still there, even though a clean sheet design would never have one.

My Hyundai Ioniq hybrid has a 12v section of the Li-ion battery that can be charged off of the hybrid battery while the car is off with the press of a button so that the car never needs to be jump-started unless the entire hybrid battery is dead.

I don't think that is what this person is talking about. Yes having an extra lower voltage battery is totally normal and every EV either has a led acid or an additional smaller LiIon battery.

Having multiple chemistries in one battery pack is of course possible, but I don't any car who is actually doing that.

Can't find it on the fly.

I read about it a few month back but ev battery and types etc. Shows a lot of other topics.

Might have been Tesla when they announced the other cell type.

As well as battery charge cycles

And shock tolerance, and temperature tolerance, and i/o efficiency

Particularly relevant for this particular battery, because the authors seem to think it's impressive that they had 80% capacity retention after 50 cycles. No, I didn't forget a zero. That's 50, not 500 or 5000. It may be an improvement on other Li-metal anodes, but it's still orders of magnitude away from being stable enough for practical use.

I'm not sure if the paper is open access or if my library is automatically logging me in again, but the cycling behavior is shown in Figure S18 of the Supporting Information here, page 12:

https://onlinelibrary.wiley.com/action/downloadSupplement?do...

Here are the specs on the Amprius silicon-anode battery, currently shipping in low volume:

https://amprius.com/products/

That's better on all the metrics you listed except cost, which it doesn't mention. Whatever their current cost is, it should drop significantly once they complete their factory in 2025.

https://amprius.com/facility/

Most of the battery is standard lithium-ion, the anode is a drop-in replacement.

It mentions lasting for 200-1200 cycles, which (besides a suspiciously large range compared to Li-ion's 500-1000 cycles) is not better on all mentioned metrics.

If it's like Li-Ion, that's full discharge and charge cycles, not every top off. So if these batteries are sufficiently higher capacity, it might make up for the difference. 200+ charges is enough if each charge lasts 2x longer or more.

The above comment didn't mention cycles but I should have said "similar or better." Cycles are comparable, seems likely it's just more sensitive to poor management. With about twice the capacity, fewer cycles are more tolerable anyway.

In any case, this looks like a very practical battery with serious advantages over lithium-ion.

If you have double the energy capacity and the same cycle. Your phone will also last roughly double the time at the same energy usage. That is probably good enough for most things.

Amprius technology will not magically drop in price as much as people think. Some manufacturing methods don't just scale and become cheap.

Their large facility planned is still tiny in terms of battery factories.

This will remain an expensive niche product.

No small company is going to suddenly build a gigafactory. But 5GWh, if they manage it, is not that small. One of Tesla's gigafactories is 37GWh.

These batteries will target the aviation market which will be willing to pay much more than the automotive segment. EV's need a certain weight for safety and once a battery pack goes lower than that weight the incentive for buying lighter batteries quickly fades.

Starting with aviation while they're at low volume makes sense. But most EVs weigh more than the equivalent gasoline cars, and have shorter range than many people are comfortable with, so I think there's plenty of opportunity for silicon-anode batteries in cars.

Personally I'd like to drive an EV 400 miles to visit my brother without stopping to charge, which realistically requires at least a 500-mile range, preferably 600 (so 80% to 20% is about 400). Charging time of less than ten minutes would make that less important to me, and conveniently, these batteries provide that too.

Actually, energy storage by weight is not as big a deal for electric cars. Regenerative braking can recover most of a vehicles kinetic energy, which is where the weight dependent energy goes. This is why several hybrids get better fuel economy in city driving than highway, the biggest losses are due to aero which increases nonlinearly with speed.

Otherwise yes, it's important to find something better without sacrificing on any of those metrics.

>Regenerative braking can recover most of a vehicles kinetic energy

I used to think that was the case, but then i think i read somewhere that it only recovers 20% of the kinetic energy. Can't find it anymore though

As with anything else it depends what you optimise for and at the most basic level the car uses the engines to accelerate at all speeds but might need to use break pads at slow speeds.

I've seen data showing ~70% recovery on a Model 3, but I also can't find the source :/

Like OP mentioned, the efficiency of recovery varies by speed but is generally in the 65%-80% range for total round-trip (the system captures ~80% of the kinetic energy but with round-trip losses, you only get ~80% of that energy to propel the car).

Maybe you're thinking of the total range boost provided by regen braking? That's often shown to be roughly 20% via studies;

https://sci-hub.se/10.1109/vppc.2011.6043109

> Simulations show that the energy reduction of the vehicles under test can be more than 20% by applying regenerative braking.

It's an older study, but they show the regen efficiency at 60% for the EcoTruck and 70% for the bus.

It is basic physic.

There is all the time friction of air and the road. You can never recover that.

And in rare cases where you actually can recover energy, at non emergency slowing down, it is probably indeed in that ballpark, wich is something(especially in city with stop and go), but not very high or much. With very high tech, you can increase that number a bit, but not worth the effort. Electric cars need good batteries and every improvement there is good.

It depends a lot on how you drive. If you do a lot of hard braking, the car will have to use a lot of friction braking. If you slow down more gradually, the car can just use regen which is gonna be pretty efficient.

Still, I'm not sure OP's train of thought holds. Mass matters because you need to spend energy to accelerate it and move it uphill. Regenerative breaking does not have 100% efficiency. Therefore, energy losses are proportional to weight. Also, isn't tire drag proportional to weight? That's a energy sink that can't be recovered by breaking.

Heavier cars are more dangerous in collisions.

The extra weight of a big battery requires a bigger frame to carry it, bigger suspension, wider tires, and so on.

I’m not really happy that some of these monster EVs are approaching 10,000lbs with fast 0-60 times. It’s like a kinetic missile that can reach a momentum capable of obliterating your average 3000lb compact car in under 5 seconds.

That is pretty much the definition of moving the goal posts?

There can be multiple reasons for heavy cars to be bad. Additionally, extra heavy cars wear roads much faster.

It's nice to have a way of recuperating energy but it doesn't solve everything.

They didn't say it solved everything

Actually if I follow the conversation, the first person said “storage density matters”. The second person said “actually it does not because the energy gets recovered”. The follow up said “actually there are other reasons why weight is a problem.”

So the first person never set goal posts around efficiency, that was an assumption by the second person. The first person could always have meant that the collision risks from heavier vehicles are higher, while the second person misunderstood their meaning. No moving of goalposts here.

In the not too distant future cities will ban large vehicles EV and ICE from the downtown core. The automotive market will then split into small city cars and bigger highway cars. In the city core roads will be covered (because no poisonous exhaust gases).

Lithium ion batteries are not a single technology and are not static. There are periodic changes that improve the batteries in various dimensions. They are constantly evolving. At the same time, it is perfectly feasible for EVs to switch to alternate chemistries a construction methods. Individual vehicles might not switch but a manufacturer could switch their product line to start using sodium or sulphur or whatever new chemistry comes along.

This Ars story talks about the ongoing improvements to battery tech… https://arstechnica.com/science/2021/05/eternally-five-years...

You're right and so is the OP.

Lithium based batteries of varying chemistries collectively in space that few other battery chemistries overlap.

Those are only a few metrics. Li-ion is not fantastic in (a) charging cycles and battery depletion or (b) fire safety.

It also depends a lot on use case; for example, for home electricity storage (like a PowerWall) I would gladly give up energy density for safety. If there's some battery tech that can handle 50000 charge cycles and completely non-flammable but weighs 100 tons and has 10% of the energy density of Lithium, I'd gladly make that trade. Maybe build part of the building out of it.

I guess LTO is right there at the moment. Even LiFePo4 batteries are a lot more safer than Li-Ion ones. From what I’ve seen, I would gladly have a LTO pack in my house.

How often will you fully cycle a home battery? At 100 cycles a year it would take 50 years to deplete a 5,000 cycle battery down to 80%. Another 50 years before it was 50%. There is no way the casing would be fully intact and the electronics even be functioning after that long.

Current LFP batteries should last multiple decades as a home battery. The already have low flammability. The price is getting more affordable. They could just be part standard of a home electric system in a decade or two, like a whole-home surge protector.

> The already have low flammability.

Low rates of spontaneous thermal runaway, sure, but they still are extremely flammable if externally ignited or physically damaged. A house fire that could otherwise be put out might turn into a full disaster. An earthquake that physically damages the battery pack could cause a fire that would have otherwise not happened. A flood or minor tsunami might allow for early evacuations and most lives saved, but now the entire town is on fire instead of just water damaged, if every house has a massive lithium pack in their basement.

The only one that I'm actively monitoring is this one because it handles the other metrics AND gives a path forward to rapid charging, which is the core requirement to displace liquid fuels. IMO any battery advance that doesn't address rapid charging is going to fall to the wayside for exactly the reason you stated.

https://www.forbes.com/sites/michaeltaylor/2021/05/13/ev-ran...