Form Energy reveals the chemistry of its long-duration battery(rechargenews.com) |
Form Energy reveals the chemistry of its long-duration battery(rechargenews.com) |
I can't even count the number of lab-stage announcements that I have seen in HN. This will be of interest only when they can get it to scale
The announcement is suspicious. "100 hours" is not a meaningful number for a battery. The numbers you want to hear are KWH/Kg, KWH/m^3, max charge and discharge rates, number of charge/discharge cycles before storage drops off, efficiency, and cost/KWH.
"That project, announced in May last year, was originally due to be a 1MW/150MWh demonstration plant capable of outputting 1MW for 150 hours straight" hints that the discharge rate may be very low.
Previous work [2] indicates serious limits on charge/discharge cycles. Like 20-30 cycles.
[2] https://phys.org/news/2017-11-renaissance-iron-air-battery.h...
I'll make a note to check back in 20 years, then. :-)
I note they don't mention charge cycle durability - for grid, you'd want 10 000-ish cycles to 80% capacity. A bit of a red flag there.
Still, iron is cheap, plentiful, and environmentally benign. Even mining and refining iron ore isn't as bad as mining for many of the other chemistries, and we already mine a lot of iron, so there won't be shortages as it scales. I want this to work.
I note the web site[1] says its areal power intensity is about 3 MW per acre (presumably 300 - 450 MWh areal energy density, given the 100 - 150 hour claim), best case. They're not going to be installing this in Manhattan.
Battery prototypes are the moral equivalent of announcing you've found a new chemical that kills tumors - in vitro.
Back then the advice from others watching battery technology? If their tech is 10 years ahead of the current state of the art, then either it will take them 10 years to produce it or they will produce it sooner by sacrificing capacity for safety/manufacturing concerns.
Another important thing to remember in any discussion about power - there is almost always a substantial premium paid for portability. If someone is feeding you PR about a stationary power system and comparing it to any household-name portable system, then you should smile and nod and keep track of your wallet as you back away slowly. They are the snake in the grass your ancestors warned you about.
People are free to upvote whatever content they find valuable.
(And the headline + post title are not misleading clickbait, which is often the case with such stories.)
[ESS] already has a factory pumping out flow batteries just south of Portland, Oregon. Its core product is the Energy Warehouse, which fits a rotund tank and several stacks of battery materials into a shipping container, along with the necessary electronics... During a June visit, I saw a test line in which robots prepared cells to be glued together into the battery stack that the proprietary iron liquid flows through.
https://www.canarymedia.com/articles/ess-is-betting-the-worl...
This sounds a bit like what red blood cells are doing during breathing.
If they're planning a pilot plant to bring online in the next two years, then they have done their due diligence and believe the tech can work. It'll be interesting to watch.
It's an engineering problem that requires financing. After that, you still need to figure out how to do it profitably at scale.
The vast majority of "the science is done" breakthroughs fail to be commercialized because they're too expensive or time-consuming to figure out how to scale, or the unit economics just don't work out.
I've seen the inside of some magical labs...Their actual setup when you stared real close and knew enough of how they were doing things was anything but.
It's even more difficult than that. :-)
Ideas have negative value; lab prototypes also have negative value; pilot plants are worth a small fraction of what they cost - scrap value.
You get value from full scale production, and every bit of that value is paid for in the engineering required to get to full scale.
That project, announced in May last year, was originally due to be a 1MW/150MWh demonstration plant capable of outputting 1MW for 150 hours straight.
If the energy had gone up 300x from the originally announced pilot project the same way the power did, this would be a huge storage project boasting 45,000 MWh of storage capacity. It would surpass big pumped storage projects like the Bath County station (capacity: 24,000 MWh):
https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta...
But this news article doesn't highlight any superlatives like that.
Reading between the lines, here's what I think has changed:
- The original announcement of a 1MW/150MWh project was an implicit admission that their battery could not charge or discharge quickly. It took nearly a week to fully charge/discharge. At the time they put a positive spin on it by emphasizing "long duration." That's not really an advantage, though. You can just discharge a high-rate-capable battery slower for long duration applications.
- Since this updated pilot project announcement touts more power and leaves any energy increase unspecified, I think that they found a way to increase the charge/discharge rate for their chemistry. That would be good because it would mean that the chemistry is suited for grid tied storage in general, more like lithium ion. If it can charge and discharge at high C-rates and it has lower lifetime cycle cost per megawatt hour than lithium ion batteries, it could be very successful.
EDIT: new user "tiddelypom" below says that he works at Form Energy and that this article is incorrect about the project size:
Not sure where that article got the 300MW number, the GRE project is on track for the original size.
If that is the case, my remarks about the limitations of batteries with low C-rates still apply. But my speculation that the company has drastically improved the C-rate of its chemistry would be incorrect.
[1] https://newatlas.com/energy/bavarian-brewery-carbon-free-ren...
What is left missing in the big picture for 100% clean, and renewable energy? As far as I can tell, Solar and Wind has already achieved cost/Wh lowered than all other form of energy and has a decent roadmap to further drive down the cost by another 50 - 60%.
Or are there some other puzzles we dont know? Or if Iron Battery works, and this will be "it" ?
- Steel production
- Ammonia production
- Organic chemicals production (polymers, lubricants, solvents...)
- Electrification of transport (world car and truck fleet is still 99% combustion powered, and these iron batteries aren't the right kind for mobile usage.)
- Synthetic fuel production for applications that can't use batteries, like rockets and trans-Atlantic passengrer flights.
- Cement production, which currently releases large amounts of CO2 from fossil combustion and from the chemical transformation of limestone.
Back to NiFe though, you can certainly get decades of use comfortably out of NiFe cells, but it's worth taking into account that they require a lot of maintenance, routinely topping up each cell with deionized water (there are automated systems you can buy or build yourself to manage this though), and every few years the KOH electrolyte inside them will need replacing every few years, plus you will want to keep your cells adequately ventilated as they vent hydrogen periodically.
I would definitely NOT recommend lead-acid, sure the upfront cost is lower than anything else by quite a ways, but they won't last long at all, and as a result I'd be surprised if you weren't paying a lot more in the long run.
https://www.alexhsain.org/blog/ironair
This could be super useful for all sorts of backup situations, from homes to data centers to hospitals.
And once they are installed generally, they can be combined together as a virtual power plant and start partially paying for themselves.
The round trip efficiency of hydrogen is already something of a concern for grid backup power, as far as I know, ans that's only slightly less than 50%.
As storage costs decrease, those moments in time when there's oversupply of energy from solar and wind will become shorter and fewer. And (at least to me) it's really unclear what market designs will be viable if we were to have, say, 3x-5x oversupply of energy capacity so that renewables' minimums still meet our needs, and what new energy uses people will come up with when the can by intermittent energy for half a cent a kWh or something.
Unless there is a regulatory blip, then there is always a cost to energy. Stuff has to be maintained, connections repaired, monitored and upgraded.
The other thing to note is that its only "free" if you own both the infrastructure and the producer. If you are doing "arbitrage" then the efficiency is your profit margin.
Also, working for 150 hours is no great feat. Just means they undersized the inverter and power electronics. If you did that with lithium ion, you’d also have much lower cost per kWh (for small systems with only an hour or two, the inverter could be half the cost or more), so going to 150 hours would also reduce costs by a lot as you’d be closer to the raw cell price.
I suspect that unless there’s a chemical reason why they have to discharge over many days, any real system is likely to be more like 12-24 hours as you’d be wasting the usefulness of the battery by picking an impractically small inverter.
Here’s hoping it’s actually a huge cell cost reduction while keeping decent round trip efficiency and cycle life.
$6/kWh raw materials, or $20/kWh for full system
(I work at Form fyi)
Are there any publicly available documents about the chemistry, or how the product compares with e.g. the ESS Inc. iron flow battery?
BTW, hydrogen-air battery = hydrogen fuel cell, if you didn't realize that.
There's some tantalising research from a few years ago that suggests it could get way better energy density, but the same comes up frequently with battery technology.
Or as Greg Lydkovsky, global head of R&D at steel giant ArcelorMittal — Form Energy’s latest investor — put it, the technology “holds exciting potential to overcome the intermittent supply of renewable energy”.
Form Energy president and chief operating officer Ted Wiley said: “We’ve completed the science, what’s left to do is scale up from lab-scale prototypes to grid-scale power plants.
“[At full production], the modules will produce electricity for one-tenth the cost of any technology available today for grid storage.”
The battery is said to work through “reversible oxidation of iron”. In discharge mode, thousands of tiny iron pellets are exposed to the air, which makes them rust (ie, the iron turning to iron oxide). When the system is charged with an electric current, the oxygen in the rust is removed, and it reverts back to iron.
Wiley said that a 300MW “pilot” project for Minnesota-based Great River Energy will be commissioned in 2023.
If the price is right, long duration is just fine. One week of storage to get through a spell of cloudy weather or poor wind conditions is quite useful. It doesn’t obviate the need for daily storage.
Coal energy density: 6.7 kWh/kg [2] Iron Ore energy density: 1.4 kWh/kg [1]
Total iron ore energy reserves: ~236.04 billion kWh [3] Total coal energy reserves: ~ 7,068 billion kWh [4]
So as far as energy goes we have 30x as much coal energy.
Now the rust can be renewed with energy ... but you need the energy to renew it in the first place.
[1] https://spectrum.ieee.org/energywise/energy/renewables/iron-... [2] https://en.wikipedia.org/wiki/Coal [3] https://www.nrcan.gc.ca/our-natural-resources/minerals-minin... [4] https://energyeducation.ca/encyclopedia/Coal_reserve
> but you need the energy to renew it in the first place.
So am I hearing you could create the iron-fuel someplace with excess energy and then ship this stored energy someplace that wants to burn it?
And while Iron loses out to energy density per kilogram, it wins on kilogram per cubic centimeter :D (your math is much appreciated btw)
Comparing for example a 100ah lifepo4 to 100ah lead acid, the useable capacity of the lithium will be close to 4x more. Using the full capacity of the lead acid will make them wear out quickly.
Basically, if you're cycling regularly (e.g. smoothing solar and wind over a day) then Lithium is already pretty good and you can expect it to get bettwr as it scales out to the entire automotive industry and indeed those car batteries will be fed by the grid and can also act as short term storage and demand management.
If you cycle less regularly though, storing power for weeks or more then you need something much cheaper than lithium can ever be but if you're cheap enough you can sacrifice some conversion efficiency and still be useful in a 100% renewable grid.
This is where flow batteries are targetting, you can have a small/cheap "converter" but store the energy in tanks longer term.
But as you say, thats also basically what you can do with hydrogen/ammmonia. And as an added bonus you can buy sell hydrogen/ammonia on the open market as it's used for other purposes, which lets you insure against under/over production and take advantage of economies of scale on the converter and storage parts.
As a final bonus, during the transition you can add a percentage of hydrogen to existing gas turbines to reduce their carbon intensity and GE and other sell turbines that are built to run on gas, hydrogen/gas mixes and also pure hydrogen. This gives an easy ramp up as a carbon price and/or minimum targets can kickstart the green hydrogen industry without any particular customer needing to bear 100% of the cost.
Methane from waste can also be used as a source of hydrogen, making it carbon negative, with a promising tech looking to generate solid carbon in the form of graphite. But even if you released the carbon I to the air it's better than releasing the methane.
Low-cost methods for its safe storage and handling are well established, despite the need of being careful to avoid leaks.
Also the fuel cells using ammonia are not too different in performances compared to those using dihydrogen.
Hydrogen might be a possible choice when high energy per mass or power per mass is desired, but it is a very bad choice for the purpose of this new iron-air battery, i.e. stationary storage with very high energy capacity and very low cost.
Iron-air might indeed be the best choice for medium-time energy storage, with low cost and good full-cycle efficiency.
For very long energy storage times, e.g. years, synthetic hydrocarbons would be preferable to hydrogen, due to much easier storage and handling.
Since water is significantly more available than just about any other material, hydrogen-air cells should be the ideal battery for anything that isn't volume limited. Which is frankly a lot of cases. Unless there's some specific need for an iron-air battery where hydrogen-air can't be used, it's hard to conceive of a situation where we wouldn't use hydrogen-air.
Synthetic hydrocarbons are basically extensions of hydrogen electrochemistry. You are just adding carbon to the hydrogen made with the electrolysis step of a hydrogen-air battery. It's even possible to make a hydrocarbon-air cell such as direct-alcohol fuel cells or solid oxide fuel cells.
Are they confused, or just lying?
If there is still science to be done, sure, higher risk, but even paying a few scientists to develop IP for 2 years is a rounding error on what investors put into novelty software projects.
That's irrelevant to this particular article because the intellectual property for this development is owned by only one company.
> if it's possible, one of them is probably going to succeed and take all
> If there is still science to be done, sure, higher risk
Yes, that's exactly what I'm saying. Your original comment implied by it's just a matter of spending enough on engineering. That's just not true.
So now you're moving the goal post and qualifying "it's just a matter of engineering" with "it's just a matter of engineering... unless it's also a matter of financing and other breakthroughs that may be needed".
> Unit economics are an optimization problem, which is literally what engineers solve, and you can hire them at scale.
Engineering doesn't just scale like that. You don't make a breakthrough in 1/10 of the time just because you hired 10x the engineers. There are lots of limiting factors beyond how many engineers you have.
> even paying a few scientists to develop IP for 2 years is a rounding error on what investors put into novelty software projects
This is just not true. The whole soft part of software is that you can shuffle around some code and have a completely different outcome.
Two years of scientific research on something hard (as in hardware) and also difficult/unprecedented is not comparable to building the next Slack or something, either in costs or the ability to staff it up. You could build a Slack clone today for <$10k and get to v1.0, and then it becomes just a marketing/sales problem.
To advance a new battery tech to a marketing/sales problem can't be done by a few people in a few weeks for $10k. It's orders of magnitude more expensive.
Fine for a trolling motor, but if you're deep cycling them in a power system, that could kill them in a couple years. Usually you'll want to size them so you never go below 50% discharge on a normal basis.
You are also right about synthetic hydrocarbons. The extra hydrocarbon synthesis step lowers the total efficiency, compared with using hydrogen.
Nevertheless, the lower efficiency is more than compensated by the simpler methods used for storage and handling, which require much less expensive materials and a much lower volume and total mass.
The benefits of using hydrocarbons for long-term energy storage have been amply demonstrated by the living beings that have been using this method for billions of years, many of which can easily achieve an autonomy of months without eating, while doing activities that would make a present-time robot using batteries inoperational after a few hours at most.
That might be partially true. Especially in the case of hydrogen-to-ammonia where the process of conversion is much more straightforward. However, storing hydrogen in salt caverns for years at a time is already proven. So further conversion steps might not prove any real value except where volume of storage is important.
I totally agree that our peak energy outputs are going to be be absolutely massive, and for the past five years have been trying to think of the implications.
One of these is that it becomes impossible for solar or for wind to survive on its own with our current market clearing mechanisms. Which for those that don't know, works something like an auction where generators each say "I can provide X megawatts at Y $/MW" and then the operators sort the bids and choose all the operators needed to meet demand, and pay everyone at the highest bid that cleared. What happens in these markets when there's oversupply is that prices go to zero. (Or even negative. When generators have external income sources from producing generation, they will pay to put power on the grid if they can get more from those other sources).
When price on the grid is free, the solar and wind farms aren't making any money. Which means that they need to recoup all their capital costs in those hours where energy is not overproduced, but every other solar and wind generator is going to be in the same boat during those low supply times, and I don't know yet if there's a market equilibrium that will both allow pure generators to survive and for customers to not revolt and override this market mechanism.
This means that either 1) every single solar and wind farm will need to incorporate storage in order to be able to ever recoup their investment, is 2) market design has to change.
If it's 1), then in that case, the inputs to storage can't be free, because a combined generator/storage arbitrage agent, you have to value your generation at some cost, because you paid free capital costs and airs depreciating.
If it's 2), then I think any market design is going to require payments for energy even when there's oversupply. I don't see how a market design with long periods of zero-cost energy can survive (though I would love to see one, it's quite likely I'm not imaginative enough for that!)!
https://www.aliexpress.com/item/1005002625171294.html
(random link, never tested this vendor).
Prices have gone up a bit in the last few monthes.
Good source of information on Chinese LFP vendors here: https://diysolarforum.com
Lead acid are still more forgiving (although with the caveat that they don’t last long even if we’ll cared for), but LFP is pretty wonderful.
It is a meaningful number... in the grid scale energy storage market. It's a term that summarizes many of the complex properties you mentioned. For a given energy storage technology, there is a certain duration that it tends to be most effective at. For traditional lithium ion batteries, that duration is about 4 hours. If you want to use lithium ion storage for longer durations than that, then you're making substantial sacrifices in cost effectiveness, utilization rate, etc.
Obviously one of the huge areas of research is long duration energy storage, to smooth over energy availability fluctuations that last weeks or months. Some might argue that Form Energy is addressing medium duration energy storage, and there isn't really any technology suited for true long duration energy storage yet.
If Form Energy's technology works out, then they're saying they've developed a battery technology that is 10x more cost effective than lithium ion on a per kWh basis, but that the technology cannot discharge as quickly as lithium ion, which makes it better suited for medium duration energy storage. You could do the same thing with Lithium Ion, it would just be cost prohibitive... 10x as expensive, supposedly.
What I've shared above is my understanding from following lots of news about green energy tech for years now, but I'm not an expert who can answer a bunch of additional questions... but your comment about 100 hours not being a meaningful number isn't accurate. It is meaningful to the target audience.
There is several missing factors here, and it’s a useless metric. Lithium ion can do ‘100 hours’ as well - based on discharge rate. It can also do 10 minutes - based on discharge rate. 100 hours is literally useless on it’s own because it doesn’t tell you anything concrete. 100 hours….. of what?
It looks like a classic science writing article where they left all the important units off, misunderstood the whole thing the audience was looking for, and made it all super confusing and pretty useless compared to an actual paper.
> Lithium ion can do ‘100 hours’ as well
Did you reply to the wrong person? I already addressed your entire comment several different ways in my original comment, and you didn't address anything I wrote in mine, as far as I can tell. Maybe I'm not the best at explaining things?
> 100 hours... of what?
Cost effective energy storage solutions that can discharge for 100 hours at maximum operating output. "Cost effective" is absolutely the key factor. Lithium ion is not currently cost effective at such durations. It is cost effective at about 4 hours, but some sources will say anywhere from 2 to 8 hours.
If you aren't familiar with a particular industry, it's perfectly logical for that industry's shorthand to sound like total nonsense. You (and most of HN) are not the target audience for a statement like "100 hour battery". Grid scale energy storage operators are the target audience, and they understand what that means. It means slow batteries, which also implies cheap, because no one would buy slower battery technology if it weren't a lot cheaper. Form Energy explicitly declares the technology to be 10x cheaper. We'll see if that holds up in reality.
Someone unfamiliar with computer science who overhears a conversation about "garbage collection" would likely be very confused. "Computers don't emit garbage! RAM is reusable, how could bytes of RAM become garbage?" But, obviously garbage collection is a real thing with computers, even if it sounds like nonsense to someone outside the industry who just knows enough to know what RAM is.
Here's an article[0] that talks about long duration energy storage, and they even mention Form Energy. Relevant quote from the article:
> Lithium-ion batteries have absolutely dominated new storage construction in recent years. But they rarely can deliver their full power capacity for more than four hours — that’s what people mean when they say “discharge duration.” Batteries technically can go for longer, but it generally costs more than it’s worth in today’s market dynamics.
One more choice quote:
> Batteries cannot yet compete with gas plants in providing prolonged power for multiple days. But a cost-effective 24-hour duration storage system could handle longer demand peaks, and a 48-hour system could do even more.
It's all about cost effectiveness.
[0]: https://www.greentechmedia.com/articles/read/so-what-exactly...
The hard part is making it cheaper per kWh.
If they made it cheaper per kWh then they should say that
They do say that. Quote from the article:
> at less than 1/10th the cost of lithium-ion
"100 hours" isn't an advantage for this technology. The advantage is the cost effectiveness. "100 hour battery" mostly means that it will take 100 hours to discharge one of these batteries (of any capacity) at the maximum discharge rate that the technology allows. Obviously that is a huge downside compared to lithium ion, which is able to respond to grid energy needs with much higher power density!
But it doesn't really matter, if the price is right. Long duration energy storage is all about lowering the cost per kWh by developing technologies that have lower power density in exchange for also lowering cost per kWh of storage. Lithium ion isn't cost effective for long duration storage right now.
Also, people in that industry know that surely no one would proudly advertise a "100 hour battery" if it weren't significantly cheaper than lithium ion on a per kWh basis, so the term "100 hour battery" also means (to the right audience) that the batteries have to be cheaper than lithium ion.
Whether Form Energy will succeed in their claims at scale is TBD. I hope they do well, because cheaper energy storage is immensely helpful for decarbonization of the grid.
Ok, then would you be so kind to show how to compute these properties from this single term?
I just love these "gotcha!" comments that pop up on HN so frequently. I'm having to explain what it means to summarize information.
Hashes aren't useless or meaningless, they just aren't a substitute for the full information if you need the full information. I'm sure that if you're a serious potential customer, you can contact Form Energy and get whatever detailed information from them that you need. Otherwise, you obviously only get the information they choose to disclose publicly.
Your desire for more information doesn't somehow make "100 hour battery" a meaningless statement. When you see the mpg rating of a car, that is a summary that has thrown away detailed test results that could tell you more about the fuel economy of the vehicle under various conditions. EPA testing involves multiple test "cycles" that represent different conditions, but you don't typically get to see the results of each cycle. People still like to see mpg ratings and compare them.
For grid scale storage, kWh/kg and kwh/m3 (actually j/g and j/m^3) are, for all intents and purposes, irrelevant -- people aren't carrying power plants around, and grid scale investment is the classic Cap Ex/Op ex carry trade.
Also your $/kWh is an input to LCoS rather than a metric that can be used to make a judgement on its own; discouragingly, though LCoS is even mentioned in the article, it's only in a wavy.
Or they just have a slow-discharge technology and are trying to create the illusion it's good for something.
> at less than 1/10th the cost of lithium-ion
That's just a PR statement at this point. They haven't built many batteries.
If the materials cost for a lithium-ion battery went down 90%, battery cost would only go down 50%.[1]
The number of "it's going to be really cheap" battery claims far exceeds the number of really cheap and usable batteries that actually ship.
Their claim is not referring to the raw battery materials. Their claim appears to be that they will be able to offer grid scale batteries for 1/10th of the cost of lithium ion, all in. Obviously, the drawback is that these batteries take over 100 hours to discharge and recharge, so they’re slow.
They are doing a pilot project for Great River Energy in 2023. That’s when we will know how real this product is.
Industry experts that I respect believe that Form Energy is very real, unlike all the vaporware that exists out there.
You can remain skeptical and dismissive if you want. It’s irrelevant to whether Form Energy succeeds or fails.
I haven’t seen anyone here saying that Form Energy has a 100% chance of success, and skepticism is warranted for any startup. Even if a battery startup has perfect battery technology, they can still fail for many reasons.
That seems like a stretch or an unwise convention. It could have some other advantage instead. Loudly proclaiming a disadvantage doesn't tell you what's good about a product, or what circumstances it's useful in.
It is what it is.
FWIW, I use HN as batting practice, to refine my talking points.
A terrific recent example is Scott Galloway advocating breaking up big tech. Observing his message craft over the years is instructive, inspirational. He now says stuff like "oxygenate the market". Brilliant.
Choice of metaphor matters. "The different between the right word and almost right word is the different between lighting and a lightning bug." -- Mark Twain (from memory)
Keep going. You're doing great!
But if you say "summary", then I'd expect at least to get some info in the right ballpark. Otherwise it is not a summary, but just some alternative bit of (possibly relevant) information.
Also, a hash is not a right analogy for a summary because typically hashes don't hold any bits of useful information, at least within reasonable computational limits.
* What's the equivalent summary statistic for an iphone battery?
* If it has the same discharge stat as an iphone battery (just picked arbitrarily for calculation purposes), the 100-hour battery's capacity should be calculable.
You can compare Form Energy’s 100 hour batteries to traditional lithium ion and see that Form’s batteries are 25x slower. That’s a valuable datapoint, and speaks to a limitation of Form’s batteries.
The time to discharge an iPhone battery at maximum supported output of the battery is entirely irrelevant to iPhones.
In your first comment you seemed to be talking right by the person, but I guess not.
Thanks for the correction.
Open question, which maybe you might have info about, I'm just curious if maybe anyone crossed something on this; I wonder if that characteristic is inherent to specific energy storage tech; for example in Li-Ion IMR/INR batteries, this might be in part because of the voltage sag and discharge characteristics? In other words, a battery that sagged less under load and had a flatter discharge curve would have a wider range of acceptable durations? For example : https://www.richtek.com/battery-management/img/battery-disch...
This graph gives a general idea of how battery performance degrades the more load you put on Li-Ion batteries, the kind in flashlights, vapes, etc. The ICR18650s of the world et al.. They are not great for energy storage, long term, frankly. The harder you discharge them, the more the voltage sags, requiring even harder discharge to maintain a proper power output, leading to more heat, and power loss in spiky demand conditions. Leaving them on but at low-power for a very long time seems to be more efficient, but by the time you hit that low of a power-delivery, they become less cost-effective, because you could do the same with a hydro plant, a reservoir, and pumps. Li-Ion batteries need management circuits, balanced charge, can be overcharged, can be drained 'till they turn into a brick. They're far from idealized batteries that discharge at all rates consistently at equal voltage all along their Wh rating. A Constant-Power drain on Li-Ion heats up and degrades way worse at low charge or low battery condition, etc.
In other words, kWh is never the be-all-end-all of energy storage. If you want long, sustained power in tiny sips, I'm pretty sure nothing beats these ZnO batteries for hearing aids that use oxygen (or is it air?) as fuel. What seems to really matter is the ability to push out kWh on a consistent basis is, as far as I can tell, and we have no really good solution for this?
Am total noob. Been learning from The Limiting Factor on youtube that many different Li-ion chemistries have different use cases, ideal applications, knock-on considerations.
Why Tesla intends to use different chemistries for car, cybertruck, semi, powerwall, etc. Why others are choosing different chemistries, like Apple and lithium-titanium, for their particular needs. (Such subtlety. Total nerdgasm. What a time to be alive.)
So your explanation makes perfect sense.
if i am using an inverter to convert DC to AC viz 220volt where my AC appliances run, does it matter on the battery side?
if i have a load, say a pc running 1 KWH, will these two battery systems run for 2 hours both (assuming discharge rate is same, i know i know, just calculating)
i am doing this because solar batteries are being sold at 48Volt x small AH to come up with KWH but at the same time lead acid are only sold at 12Volt but high AH. what if i buy 7AH 12Volt x 25 batteries to get same KWH?
does battery voltage or amperage matter when converting to AC? how does that work?
oh, BTW, i have a 5.2KWH solar array that is grid tied
Higher battery voltage == less copper, smaller wires for the same wattage. Sometimes also a bit more efficiency too (less resistance, smaller absolute voltage drop moving current around).
Your units are a bit messed up load wise - is your computer running at 1 kWh per hour? For how long? (Yeah, that is confusing - but that would be the energy used to power a 220 volt, 4.5 amp load for an hour, every hour).
One of the confusing things with some of these units is kWh is a measure of energy, even though it has a time component in the name (kWh can be directly converted to joules). It isn’t ACTUALLY a measure of power (aka energy over time), even thought it implies it is because it has ‘hour’ in the name.
Power is energy over time.
So you have an absolute number for storage (your battery in this example can store 2.1kWh of energy - 2.1kWH is equivalent in energy to 2100 watts drawn out over an hour).
Your inverters, panels, chargers, etc. will be rated for a level of output POWER (energy over time) then will draw/convert that (say 4 or 8 kw) to/from the batteries. You can easily have an inverter that can draw down those batteries super fast (say will pull down 8kw continuous, so you’d get less than 15 minutes on that battery - if it doesn’t get damaged or explode), or one that draws power out slowly (say 200 watts max) to make it last 10 hours say.
Same with your chargers, etc.
You’re solar panels are almost certainly not rated in kWh, but kw- aka maximum instantaneous power they would be producing at any moment under ideal conditions, not aggregate energy they would be producing or storing over time. This is important because they don’t store power and actual energy production will depend on a lot of factors, like amount of time in the sun, etc.
I am aware of the solar thing. I have a grid tied system and I sell the energy to grid. I produce around 30 kWh a day which is good.
My problem is storage. If I want to store energy, should I go with 48volt 24 ah battery or 12volt 96ah ? As I said, there will be an inverter giving 220volt output so does battery voltage matter?
For storage, none of that matters. What you need to look at is the cheapest total capacity in kWh after accounting for conversion losses at your median discharge rate. Let’s say your median consumption is 450W, then you see the efficiency of your inverter with 12V vs 48V input to produce a sustained 220V at 450W. Maybe it’s the same efficiency for both 12 and 48v or maybe one is 85% and the other is 80% so you need to multiply the capacity by that amount to get capacity after inverter conversion losses to account for the only difference between the two setups.
