Transcription
So, in today's video, we're going to learn about sodium ion batteries and why they're a horrible choice for off-grid solar power systems. Every few days, I get someone commenting saying, "Why aren't we using sodium instead of lithium? Isn't lithium just so bad for the environment and we can't find it anywhere?" So, today we're going to talk about lots of misconceptions and why we don't use sodium ion batteries and why there's even better options than sodium ion batteries that no one even talks about. So, let's get started.
So, first off, the roundtrip efficiency of a sodium ion battery is pretty bad. Some of them are even worse than a lead acid battery. On average, it's 60 to 85%. The best figure I could find at a slow rate was 92%. A lead acid at a high state of charge is around 60%. But at a low state of charge, it can be upwards of 80%. The efficiency of an LFP battery is 99%. And even at high rates, the worst you can get is like 95%. They're very efficient. And for an off-grid solar power system, this loss is substantial. That means that you need to spend more money on more solar panels, a larger solar charge controller, and more batteries, 20% more.
Next, a sodium ion battery has a faster cycling degradation rate compared to a lithium battery. So, typically with a sodium ion battery, you can expect 2,000 to 5,000 cycles to 80% capacity. But with lithium iron phosphate, it's 5,000 to 10,000 cycles. Now, with the latest cells, again, that's to 80% capacity. You can still use the battery in both instances safely, but you're going to have a faster cycling degradation rate.
Next, for the given weight and volume of a sodium ion battery, you get less energy storage. A lithium battery can hold more energy with less weight and less size.
Next issue is the voltage curve. You do not have a consistent voltage. It's very linear and it's very wide. And it makes it very difficult for inverters to have the same performance over the whole state of charge. And this is one of the main reasons we don't use lithium titanate oxide batteries. The voltage range was so hard to work with that we couldn't find inverters to use with it. We found ourselves not able to use the full capacity of our battery bank because of the voltage curve. Now, some inverters just work well with a wider voltage range. Victrons are pretty good in that regard, but you have to check. Some of them just won't work that well for that application. Lithium iron phosphate works with all inverters really well, but it's very different for sodium ion batteries.
Also, a long time ago, I used to use Tesla battery packs, and that's NCA, nickel, cobalt, aluminum. And what's interesting is it had a very linear curve, and all the 24-volt inverters that they had for that pack nominal voltage just wouldn't work. I could only get like half of the usable capacity. So, if you have an inverter that works for your battery bank, you could easily use sodium ion, but you're not going to get the same performance that you get with lithium iron phosphate, for example.
Now, why do people like sodium ion batteries? The first reason is cold temperature performance. And CL actually came out with a sodium ion battery that can charge and discharge at -40° C. But luckily, we now have heated batteries. If you're in a cold temperature, you can easily make a lithium battery work just fine.
Next reason is lithium availability. Everyone sees, oh, there's a new lithium mine that they just found. It could make all of these batteries, but lithium availability is not the issue. It is processing at large volumes into a purity that you can use for manufacturing. That is very difficult, especially at large volume. Also, lithium is only 2 to 7% of the total cells weight. It's pretty small. Usually, we run out of nickel or other things when we make lithium batteries. Not lithium. Some years ago, you kept hearing about it because it was an issue then, but now it's all caught up and that's why you don't hear about it anymore.
Now, some methods of extraction use a lot of water to get lithium and that's an environmental argument. But guess what? We have new ways of processing lithium straight from sand with very little water and very little environmental impact. So, as more of those processing centers start to come online, I don't think we're going to hear about it much. And that's what they're doing in Texas at the Tesla plant. That was the whole point of that. They mentioned it at battery day, but are they doing that in China? I don't know. There's only so much I can prove with the internet unless I actually go over there.
Next, sodium ion batteries are very safe when it comes to fire risk, but so is LFP and lithium titanate oxide. They're even making LFP as safe as LTO now, which is crazy. Look up the BYD blade pack and also look up LTO destructive testing. You can drill through it. It doesn't have a self-propagating thermal runaway effect. So yeah, those arguments really don't hold up. We already have that for lithium ion chemistry variants.
Now, personally, if I think you guys tried out a sodium ion battery and you saw that bad performance and you're used to lithium iron phosphate, I don't think there's no way you can go back because it's pretty much like going back to lead acid batteries, just with less maintenance. And I would love to be proven wrong on any of these points, but guess what? The voltage curve and the roundtrip efficiency, they're not going to be making that many improvements to that. And for off-grid solar, you're going to have to plan accordingly and make a larger system with more solar, more battery, and more solar charge controllers.
And some years ago, when I was experimenting with LTO batteries, all of those reasons are the reasons I didn't use them. So, I really don't think people are going to use sodium ion batteries for off-grid solar systems.
Now, for grids scale batteries, if someone can find a way to reduce the cycling degradation rate, they won't care about roundtrip efficiency. But why not use LTO instead? You get way more charge cycles and that can be upwards of 20 to 30,000 cycles. Also, it has really good low temperature performance. Also, the discharge rate is incredible. Also, the cooling efficiency is better, but the voltage curve is awful and that's why we don't use that chemistry either.
All of these reasons are why we use lithium iron phosphate. That flat charge and discharge curve is so nice to have. I don't think people understand that because we're getting used to these LFP batteries, but they're phenomenal.
Now, whenever you see a new battery technology on the internet, just Google the downsides because I promise you they're missing something. Sometimes a battery will have a really good charge cycle life, but it has horrible efficiency or it's good in one way, but it's very large and heavy. So, that you'll never really win with batteries. It's just the physics of these electrochemical reactions. There's only so much energy you can cram into a space. And a lot of times to reduce the cycling degradation is very difficult and it requires a lot of engineering. Lithium batteries are incredible in this regard. People don't understand how good they really are.
So again, question everything that you see online. Don't see some YouTube video and be like, "Oh, this is going to fix everything." Because it probably won't. So thank you so much for watching my video and I will see you in the next video. bite.