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 got 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 :(
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.
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.
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!
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.
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.
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.
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.
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…