These days just about any battery storage solution connected to PV solar or similar uses LiFePO4 (LFP) batteries. The reason for this is obvious: they have a very practical charge and discharge curve that chargers and inverters love, along with a great round trip efficiency. Meanwhile some are claiming that sodium-ion (Na+) batteries would be even better, but this is not borne out by the evidence, with [Will Prowse] testing and tearing down an Na+ battery to prove the point.
The Hysincere brand battery that [Will] has on the test bench claims a nominal voltage of 12 V and a 100 Ah capacity, which all appears to be in place based on the cells found inside. The lower nominal voltage compared to LFP’s 12.8 V is only part of the picture, as can be seen in the OCV curve. Virtually all of LFP’s useful capacity is found in a very narrow voltage band, with only significant excursions when reaching around >98% or <10% of state of charge.
What this means is that with existing chargers and inverters, there is a whole chunk of the Na+ discharge curve that’s impossible to use, and chargers will refuse to charge Na+ batteries that are technically still healthy due to the low cell voltage. In numbers, this means that [Will] got a capacity of 82 Ah out of this particular 100 Ah battery, despite the battery costing twice that of a comparable LFP one.
Yet even after correcting for that, the internal resistance of these Na+ batteries appears to be significantly higher, giving a round trip efficiency of 60 – 92%, which is a far cry from the 95% to 99% of LFP. Until things change here, [Will] doesn’t see much of a future for Na+ beyond perhaps grid-level storage and as a starter battery for very cold climates.
Thanks for trying as an early adopter to Will!
But give the new battery technology a bit of slack here please!
In some months, existing chargers will be able to adapt or new chargers appearing on the market, able to handle the differences in SOC-to-V curves.
Price point for the new battery chemistry should come down also quickly when production capacity is ramped up. Especially with the much cheaper resources for sodium batteries in mind.
I am really looking forward for buying sodium batteries in the next years!
Especially for solar systems and applications where the more limited capacity/weight and/or capacity/volume relations don’t matter :)
Yeah, I see the voltage curve actually as a benefit, because it makes it much easier to determine how full a battery is. It should be a non-issue for chargers and inverters designed to support the battery type, as they all use SMPS anyway.
The internal resistance losses are an actual downside when used for higher charge/discharge current applications.
internal resistance may not be all bad, since higher internal resistance used to come with lower self discharge … if that applies here, my knowledge base about that was somewhat flattened when a dinosaur stepped on the library :(
That internal resistance thing may be both good and bad? I suppose that also means less runaway currents? But with enough in parallel this can be overcome and it’d be a non issue? My hone connection is 230V @ 30 amps, you probably want 15 or so of these when doing a 48V system anyway, so is it then still an issue?
The efficiency losses are sad though of course. I wonder if that is something chemical or something that can be improved over time…
in the Alkaline days it was about ion mobility in the separator: high ion mobility meant low resistance, but also high self discharge; low self discharge was archieved by lower ion mobility separators, at the cost of higher resistance
Sodium ion and Iron redox batteries are designed for very large scale energy storage…commercial to utility scale.
Even in home use – nobody is using 100ahr batteries for energy storage in their house. Tens of KW/hrs of batteries is more like it. When you have that many batteries, internal resistance of an individual battery isn’t a big deal.
This is why “influencers” should not be treated as experts or authoritative sources.
I don’t know. Near 1C discharge is common with my powerwall 3. Charging is 0.5C.
The linear voltage curve is annoying because to generate the same output power with an inverter you need to pull an increasing amount of current as you go down the voltage curve. This means more serious wiring, unlike with the rather constant voltage and thus current of LFP.
True, to get the same losses in the wiring at the low end you’d need to increase the conductor diameter by ten percent.
Conversely, you win at the high end, where the voltage is higher, so losses are lower.
But if you’re getting significant inefficiency in your system due to the interconnect conductors, you didn’t engineer it very well in the first place.
I would deal with the discharge curve by load shedding when the battery discharges.
nope none of that is true and if it did be more expensive
Interesting, whole point of Na+ batteries was that they can be cheaper as NaCl is easily available. Maybe economy of scale is still isn’t here.
Yeah, economy will come next year when production lines ramp up. I highly disagree with “Will” about the usability of this new sodium tech. He made way too hasty review without considering even few months forward.
You may be right but he’s testing this product as it is now
The only Na+ drawback I see is the price. Advertised as cheaper alternative for Lifepo 210Ah cost mot than lifepo 320Ah. You sacrifise 20% of it on low SOC – so real price is 2x for Ah/$. But if consider technology as it is – lifepo is not for all climates, if you don’t want huge battery IN your home. Na+ can work in shed to -15C, and lifepo heater will consume more than solar can produce at this cold shady day. So I’ll choose to store 5kWh in sodium than heat 70kg of lifepo to +2C just to start charging. The only thing – it should be cheaper than lifepo, and it’s far from even same cost per Ah for now.
Houses most like would end up mixed. Thermal battery for when water needs to be heated, rather than going through any conversions. Same with keeping house warm.
+2C isn’t that hard as long as you have water — fill an old bathtub standing in the same room and toss the ice every morning, the losses in the battery may suffice for the rest, perhaps place them in an isolated cupboard (which may be an old fridge)
I thought the main advantage of Na-ion batteries was eliminating the reliance on lithium, for which the market is almost entirely reliant on a single country, where the lithium is mined and processed by “reeducated” citizens, and it’s all done with no environmental concerns leaving a big mess on the environment and affecting people living there. And that’s before we get into the political risks on relying on a single provider. And the cost of them is falsely deflated by that government pushing their own trade agenda.
Hopefully in time we can improve the capacity and efficiency of Na-ion, but regardless there’s reasons right now why people might prefer it.
This. I think a few percent drop in efficiency is worth your battery being made out of table salt instead of the product of slaves of a repressive regime.
Also, complaining that the charge circuits designed for lithium don’t get as much energy out is completely dumb — if you change the battery chemistry, you gotta change the charge/discharge circuit. The fact that it works at all with a lithium charge circuit should be touted as a bonus.
Chile is a bit past those days! Though the environmental mess is very real.
Ah, yes, Australia is such a problem (no #1 producer of lithium). Chile and Argentina maybe more so (#2 and #3). Oh, I know you mean China, but it’s not the largest source for lithium. Rare earths perhaps. Just a Google search will show you these results.
I had no idea that Australia was such a repressive regime. Thanks for the education!
Yes, I feel so oppressed
It isn’t just the price. It is also the fact that sodium is inherently safer, without that annoying concern about it catching fire. It also works better at lower temperatures too, which is great in residential areas in northern latitudes.
How is sodium “intrinsically safer”? It’s quite a bit more reactive than lithium.
A school classmate discovered how reactive it was when he smuggled a marble-sized lump out of a science lab in his pants pocket. He liked the demo the teacher did, of dropping a pea-sized piece into water, and wanted to do it at bigger scale himself at home. He got a bit of a surprise when he built up some sweat later. Not a Darwin winner, but I’m sure it was an education.
Pure sodium isn’t intrinsically safer, but sodium ion batteries are compared lipo. If you want to make your own bid for the Darwins try banging a nail through each of them. Start with the sodium ion so at least you’ll last long enough to find out how much safer that is than doing it with a lipo.
Hunh? I have put a nail through pouch-type lipo batteries. Several times, “for science”. A few sparks and a puff of smoke once, but no fireworks, ever. Same with dead-shorting them. They get really hot, they puff up and leak probably noxious stuff but, again, no outright flame or explosions. Ever.
I agree there’s a scary amount of stored energy in the things, and I’m still wary and treat ones in service with resepect. So, not to say a large, new, fully-charged battery lipo won’t catch fire if maltreated, but in my experience it’s hard to trigger them to make a viral video.
I nicked a LiPo battery while dismantling a vape and it rapidly and cheerfully caught on fire, you should try better batteries.
Maybe order the cheapest bike battery off AliExpress, that should be more fun.
(You should look up what survivor bias is – “well, I’ve never had a LiPo catch on fire so therefore they are perfectly safe and all those fires I’ve heard about are fake news”)
The qualification test procedure for the old Thundersky LiPO cells included shooting them with an AK-47 and verifying no sustained fire or explosion.
If you’re referring to China, I think you’re mixing up lithium with rare earth elements…
https://en.wikipedia.org/wiki/List_of_countries_by_lithium_production
I like the “reeducated”.. good catch !
And we shall not forget other mineral like cobalt. if not mined in reeducation center, EV would cost 5 to 10 times ( if not more) more than the actual price!
Just like uranium, when France “lost” mining “contract” with Mali. Not lost really but now sold at market price, so 200x more than “the good old days”…
n 2023, Australia produced 74,700 tonnes, which was 51.0% of the global total of lithium ore ( more than China ) I may be a repressed old bloke, grizzling about locsl government, but my acquaintances here seem to be a laid-back lot, not so much *reeducated” as uneducated.
China may do most of the refining, but are your claims correct?. Perhaps some re-education would help you?
I have tried an Na battery last year. Worked as expected. It was a 30Ah motorcycle style battery. 12 volts solid and ran our field test unit without a hiccup for days. We never got into the recharge realm of testing as the price point right now is significantly higher and supply was limited. Good test so far. Mains powered battery conditioner had no problem recharging the battery.
Very useful to know this early test of sodium batteries. My students and I are building a sustainable small house which is off grid and ADA compliant. We have >10kW of solar PV but only 25 kWh of battery storage. We have been waiting to see if the cost of Lithium batteries would go down. Do you have any suggestions on how to increase our storage capacity without breaking the “piggy bank” like from a used or wrecked Nissan Leaf or Arriva EV? Thank you. Bing Chen
25 kWh will last for days.
For houses that burn less than 12.5 kWh per day, that is. And I suppose that covers many houses, particularly smaller ones or those with fuel-sourced heat. A couple of previous houses I’ve lived in would draw well in excess of 100 kWh/d for several days per year, and more than 2000 kWh/month in Jan & Feb (yes, electric heat).
You want about 10 days of reserve capacity. If you use 5 kWh/d you’d aim for 50 kWh of storage. My current house eats about 10 kWh/d, so that 25 kWh wouldn’t cut it. Heck, that 2.5 kWh/d doesn’t cover ordinary networking and computer use, let alone a fridge & freezer.
Fridges & freezers really don’t use that much power.
My two fridges and one upright freezer draw a total of 3 kWh per day. The freezer accounting for more than the two fridges combined.
I need to figure out how to reduce the self-defrost cycles. Turning on a 700 watt heater inside a freezer twice a day is ridiculous, especially in the dry season.
Nothing like a bit of bias. Fridges & freezers use a lot of power because I have three of them.
You made an unqualified, qualitative assertion. An opinion.
Engineering is based on numbers. I provided some. Don’t be an ass.
Just one larger fridge and freezer is going to eat way more than Paul would comfortable with on that battery when aiming for 10 days of capacity and doing anything else at all. Ballpark of the official rating for the handful of brand new ones I’ve looked at to back of the envelope the numbers are 150kWh per year each – so in that 10 day window its about 10kWh for a fridge and freezer or getting on for half the battery capacity just for them… And my experience with the new fridge we needed recently is those ratings are hopelessly optimistic, presumably tested assuming its never ever opened, or having anything not already really cold put into it, so using that one example and extrapolating I’d say you are needing more like 15kWh minimum allowed for actually living with just one fridge and freezer across those 10 days.
So maybe 25kWh is good enough for folks like Paul, but only if you have no other demands for power or are happy with less than 10 days of reserve (personally I think 10 days is kinda excessive for most, but what works for you is going to vary) as you really don’t have much headroom for everything else on top.
And if your still using your old reliable electric that just won’t die but probably isn’t quite as efficient (which you should if you can)….
I’ve lived off grid for about 16 years and I use 25kwh a day. My 500 gallon hot tub heat pump is the main use besides a heat pump in my living quarters.
2016 18 kw Chevy volt battery now , started with lead acid.
I live more than confortably with a 375Ah-24v leaded wet traction battery, 1,5kw of solar panel and off-grid. 100Ah 24v was fine but i got a good deal on the pzs 375Ah.
I use Ah unit because It’s just the right unit in international unit system. if you don’t understand why kWh is not a valid unit, i’m so sorry for your students…
Curious notion. Please enlighten us ignorant ones: Why is the kilowatt-hour is not a valid unit for discussing a quantity of energy? Because Ah certainly isn’t a unit of energy usage.
The Ah is useful for tracking the charge in and out of a battery, but the Ah coming out of your solar array isn’t the same number going into your battery (if you have a decent MPPT charger), and certainly not the same Ah feeding your AC loads after the inverter.
Actually, the number of Ah coming out of a rechargeable battery is very close to the Ah you put into it, differing only by self-discharge of the cells, and this has nothing to do with the charging method. It’s due to the chemical reactions that absorb an electron when charging and release one when discharging. The number of kWh coming out IS lower, because the discharge voltage is always lower than the charging voltage.
So, in fewer words: ” Ah is useful for tracking the charge in and out of a battery”
and, kWh is useful to measure actual battery efficiency.
Got it.
Sorry, I misread your comment – I thought you had said that the Ah coming out of the battery wasn’t the same as the Ah going into it. Apologies.
Oh wait – that IS what you said.
Ah (or As) is relevant at the battery terminals, in general its different on the other side of the inverter (at the solar array terminals). That’s why I can’t comprehend the “mAh” rating of USB power banks: is it at 5V? Or at the internal battery voltage? Just quote the energy and expected lifetime in Full Cycle Equivalents and calendar aging. You don’t? I won’t buy it.
Matthias: It’s simple: people know the term “Amp-hour” from car batteries, (because that’s what solar power started with, which were always rated in Amp-hours), and they have a sense of how much power a 100 Amp-hour can provide for how long. This actually makes some sense on the low-voltage side of a solar power system, because the charging circuits are rated in Amperes, even if the same charger can be used at multiple voltages. This helps because knowing how much charging current you have to carry, determines things like wire gauge to the batteries and voltage drop across those cables.
On USB power banks, the mA-hr ratings are just marketing-speak, because they want the numbers to be as large as possible. Again, we are familiar with how much an Amp-hour is, so we have this misleading thing with power banks because their ratings are the ratings of the batteries themselves, which keep in mind are nominally 3.6V. And since this has to be boosted to about 5.2V in order to charge your phone, the number of Amp-hours available are lower, first because of the change in voltage (a factor of 0.7), and then by the efficiency of the boost converter, typically about 0.8, for an overall derating of 0.56. You’re not going to convince any maker of phone chargers to rate their charger at 5600 mA-hr when they put 10,000 mA-hr of batteries in it! And nobody has a clue how many watt-hours it takes to charge their phone, anyway. Few phone makers even TELL you how big the batteries in their phones are.
Note that in solar power installations, storage systems ARE (correctly) rated in kW-hours, regardless of individual battery ratings and low-voltage-side nominal voltage, and even though this again is before the inverter, with typical inverters running at around 90% efficiency, it at least gives you some idea of how long they can supply how much power.
Why It’s not valid? It’s so easy to find answer to your question that it can be a good homework for student. It can be useful to teach them why the international unit system have been created and why It’s a good thing to use it and not a curious notion.
That’s not a useful reply.
Ah x v = Wh
The correct Si unit would be Joules
Exactly!!!!!
Good luck with that. Most people have no idea how much a Joule is. And btw, the correct SI unit for force is Newtons. How many people use THAT in everyday life?
A lot of the upvoming systems are LFP and sodium hybrid systems with a mix of batteries to get the benefit of both.
Na is new so it will be a few years before they get cheap and the tech refined. Even then remember how much of the cost is now in casings, cables and power electronics that isn’t getting cheaper.
How the heck are they doing that? Separate inverters for each battery type? You can’t just put LFP batteries in parallel with sodium and expect that to work.
The charge curve for sodium is similar to other Lithium chemistries like NCM and NCA which worked just fine in battery storage before LFP got super popular. And sodium is way better in freezing temperatures; battery storage is often mounted to the outside of the house and exposed to the cold temperatures in winter.
LTO batteries are also around (they can be bought in 18650 or bigger from China). Their temperature range is huge. Price wise there shouldn’t be a too big difference: both are exotics.
Coulombic efficiency can be improved by limiting maximum charge, to let’s say 80% to 90%, as many of the losses occur at higher voltages. This will reduce the effective capacity since you don’t use 100%.
Additionally pulsed charging may improve efficiency too.
Man. So, first off, a test of Na battery with non-Na charger is completely valueless. But more than that, it didn’t even contemplate the only two questions that really matter: longevity (cycle count) and fire safety.
I think the practicality of Na has yet to be proven but this video is neither here nor there.
A more fair title would be “don’t use as a drop-in replacement – get a proper BMS”
I’m sorry but saying “the only two questions that really matter” are cycle count and longevity is so far beyond simply ridiculous that I literally cannot believe that you actually think that. More ridiculous than testing sodium batteries with lithium management equipment. If you cannot communicate your actual intent, nobody will take you seriously. You may have some points, but they are BURIED under the rest of the statement, and not evident.
If you aren’t thinking about durability and safety then you’re chasing a mirage. Very common failure in tech.
Yeah, like: I’ll charge and discharge this battery using equipment designed for a completely different discharge curve, then I get disappointed for it not working well. DOH! slaps fohead
Clearly a comment provoked by the propaganda of an different kind of regime.
Seriously, is it something in the fast food?
Why didn’t you test recent CATL battery…
Battery tech is evolving fast…
Yeah this. CATL haven’t released the specs publically yet AFAIK but they claim to have addressed all these issues.
What a funny srticle. “Battery chemistry A is terrible because my battery chemistry B charger won’t charge it properly!”
As for the internal resistance, I’d like to see physical reasons why that should be higher and can’t be similar to lfp, rather than measurements on one specific battery. Car manufacturers are talking about using this chemistry, so it seems to me that their engineers think internal resistance is not going to be a problem there.
As for cost, would be good to look at the bulk price and the global supply reserves of the various ingredients that go into making the different batteries to get an idea of what the actual cost will be, rather than taking a commodity item and compare it to an experimental prototype.
I’ve got 2 questions:
how much could this difference be due to different maturity between technologies? can we expect the Na-ion curve to get flatter in coming years?
how easy is it to design devices taking this into consideration? ie. can we make devices that make better use of a wider range of voltages?
— one minute later —
this is what Claude has to say:
The flat voltage profile of LFP is fundamentally tied to its chemistry—specifically its two-phase reaction mechanism during charge/discharge. This is an intrinsic property, not just a result of optimization.
Yes, easily. Most battery-powered devices already handle varying voltages using DC-DC converters (buck, boost, or buck-boost converters). These are mature, inexpensive components.
“The reason for this is obvious: they got a very practical charge and discharge curve”
Ugh. “They got”?
“they’ve got” or “they have”, please.
Also, I am not sure I would trust any battery, or indeed any product more complicated than a paper bag, made by a company with a name like “Hysincere”. Although I suppose it’s a step up from the usual Alibaba/Amazon “mash a keyboard and use the result” company names like LUGHFAO or WIJKWRBL…
You’ve got a sad time coming up in the near future, when you realize that the notion that Chinese products are universally inferior to American-made ones. For two reasons, in fact: 1) Chinese production quality has improved vastly over the past few years, as a result of building almost everything in America, and 2) Americans can’t seem to build anything any more, and appear to have lost some of the knack.
But cheer up – I got over it, and you will, too.
Er. The notion .. is out of date.
Sodium ion? We lost Natron in September. It’s rude to speak ill of the dead, you know.
Seems like they would work great in open loop, voltage controlled systems( like we all did for decades with lead acid).. Just about any charge controller should perform well especially a decent mppt one like victron, midnite, outback, etc. The drawback I see is lower charge rates( like lead acid), and less reliable SOC readings(dependent on shunt type meters).
With a energy harvester (TI BQ25570 for example) you still can use this kind of batteries (also LTOs). You can specific the fully and empty threshold with resistors. It can boost lower voltages to your “working” voltage like 3.3V.
Problem: That IC is old and not cheap.
I see a great oppertunity in using sodium carbon based cells for grid storage, both small and large scale. Mainly benefitial for cold climates but as sodium cells seems to also be better at handling high temps I don’t see where lithium cells would be better if efficiency improves a bit, I’ve seen real world tests with roundtrip efficieny at 93% which is not far of from lithium at good surrounding conditions.
One of the main benefit for grid storage is that existing bidirectional inverters are already in general capable of a huge voltage span, generally around 100-200v to 800-1000v, I guess that the inverters efficiency is not the best at the upper and lower regions but probably not needed strech that much to adapt for a sodium pack. Larger scale gridstorage now adays have HVAC systems running most of the time to keep the system read for a quick power ramp up, which brings the overall efficiency down and for smaller systems HVAC is not worth the investment and complexity. Not sure about sodiums roundtrip efficiency in colder temps but I guess it’s not worse than litium, and in general to be able to deliver power and energy in the cold seems more valuable for the grid to me. At least CATL Naxtra promises better cold temp efficiency, looking forward to see real world test of them, I guess there are some parameters that are not extrodinary and not presented in the PR claims.
A few points;
I’m still interested in Nickel Iron for a home powerwall. Yes, I know the reasons that they suck. But a lot of that doesn’t apply when you only need them to last the night until the sun comes out again and you have lots of space to put them and aren’t going to move them.
Having batteries that my great grandchildren could inherit and use like they were new and not getting a superfund site if the fluid got out… sounds amazing!
Years ago a company I worked for had a UPS with nickel-iron batteries, no idea why. They were really expensive. You can still get them from China, still expensive last time I looked.
As you say yeah they suck but they last forever.
Well will doesn’t live near a lithium mine or come directly in contact with the externalities of lithium mining.