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So Tesla's Li-ion batteries are going to have a significantly higher mass energy density - these are around 150Wh/kg vs 230Wh/kg that Tesla can currently muster
by sudosysgen 5y ago
So Tesla's Li-ion batteries are going to have a significantly higher mass energy density - these are around 150Wh/kg vs 230Wh/kg that Tesla can currently muster. This is somewhat mitigated by the fact that LiFePO4 handles 100% charges and 100% discharge, so in practice the protections on Li-ion means you can only really get 190Wh or so out of them every day, significantly narrowing the gap.
However, these are going to be ~4x cheaper for the same capacity, and are much safer, so some weight might be gained, but they won't take more space, possibly less space because they are prismatic.
To give you an estimate on the possible cost savings, BYD has it's own EVs, and the one they are releasing using these batteries costs 20 000$ before subsidies for 51kWh.
LiFePO4 also has much higher durability - that means that you can get away with more efficient pack designs, and probably that they can handle much faster charging.
- r00fus 5y agoIron based batteries also remove cobalt and nickel requirements, making them less environmental and politically difficult. Anything to make EVs more mainstream has my interest.
- sudosysgen 5y agoAbsolutely, it's a big part of why they're cheaper. I just wish I could actually get them for reasonable prices in smaller quantities. I have to pay a 3-5x premium for LiFePO4 batteries. I'd love some at a reasonable premium for my ebike :)
- dylan604 5y agoeBike batteries are as unique as all of the power tool ones so that they are all different. what's your approach to housing and connecting your DIY battery for your make/model? i just recently became an eBike owner as well, and a second battery pack is 1/3 the price of the bike.
- sudosysgen 5y agoI built my own ebike. I can basically make the battery pack into any shape I want. Right now I run 14s10p 18650s - it cost me 200$ to make and it has as much capacity as 3000$ worth of Bosch powerpacks. Secondary battery packs are so expensive because of DRM and lack of interoperability. I could make for 100$ a battery pack that Bosch sells for 900$. You're really not paying for the cells. Power tool batteries aren't really unique either btw. The shape is slightly different but they're all just 2p-3p 18650s with basic slot connectors.
- dylan604 5y agoI don't care what is on the inside of the battery itself if the shape of the battery doesn't fit what I want to use it. I'm pretty sure this is everyone's definition of unique battery per vendor.
- sudosysgen 5y agoWell you should - the fact they're pretty much electrically identical means that you can confidently buy off-brand batteries if they have good cells and that adapters can be possible.
- dylan604 5y agoI think you're missing the point focused on your point. We all understand the internals are probably coming from the same factory line. The problem is that they don't connect universally. As someone up the chain elsewhere stated, if the markets can be forced to use the same USB charging port, there should be a similar regulation for these kinds of things as well. Whether that's a universal battery shape/connector for tools, eBikes, whatever. We've unified things like 110v mains plugs, 220v mains, etc. The fact that they do all use the same internals makes this even more egregious.
- sudosysgen 5y agoThe internals are completely interchangeable. You'll even find the same model with different internals. I agree with you 100% about the need for regulation.
- jacquesm 5y agoSome pretty good deals here: https://www.nkon.nl/rechargeable/li-ion/chemie/lifepo4.html https://www.nkon.nl/rechargeable/li-ion/chemie/lifepo4.html
- sudosysgen 5y agoHmm, it's better than others, but I can still find Li-ion for a better price. Besides, I'm outside of the EU, I can't imagine the shipping costs haha
- jacquesm 5y agoAh yes, that complicates matters considerably. And true, Li-Ion is still a better price (and higher density to boot). But it's worth monitoring this because at some point there will be a crossover.
- sudosysgen 5y agoIndeed there will be. In North America, batteryhookup.com has A123, Headway and CATL cells at a pretty okay price. The CATL cells still aren't worth it IMO, but the Headway LiFePO4 cells can push a ridiculous amount of current, something like 200A from a single cell.
- jacquesm 5y agoYes, they're crazy. Batteryhookup is an interesting company, they're very well known in the homebrew powerwall scene. Here's to hoping that the next battery revolution will come in on time and that we'll see some real economies of scale here.
- danans 5y agoAdding to this info - LiFePO4 batteries are far more chemically stable and therefore need no cooling system. I have LiFePO4 home backup batteries and they are completely passively cooled.
- AYBABTME 5y agoAdvice on legitimately adding this to your house in a DIY manner? Or is it the kind of stuff you 100% need to hire licensed folks for legal reasons? I built offgrid systems for boats but now I'm considering doing my house.
- danans 5y agoEnphase has a self installer certification program that I used to DIY the design. I still hired a licensed electrician for the physical installation, though.
- nathannecro 5y agoI'm in the market for home backup batteries and was wondering if you could namedrop the mfgs of your batteries if you were satisfied with them.
- krasin 5y agoI highly recommend Will Prowse's channel who extensively covers batteries, solar panels, invertors and other home solar stuff: https://www.youtube.com/c/WillProwse https://www.youtube.com/c/WillProwse
- nathannecro 5y agoPerfect, thanks for the recommendation. Looks like I'll have quite a few videos to watch.
- AshleyGrant 5y agoYou're opening a whole can of worms in trying to decide what LiFePO4 batteries to buy. There's tons of options, prices have been dropping precipitously this year across the board. The first question to ask yourself is if you want the comfort of a high quality warranty or would you like the cheapest possible price per kWh? In my RV, in May, I went with somewhat high-end Battleborn Batteries. They have a great warranty, which has come in handy as one of the batteries I bought experienced an issue and needed to be sent in for repair. They paid for shipping in both directions. That being said, nowadays even just a few months later, I might decide to "self-insure" given how good the cheaper batteries have gotten.
- kemiller 5y agoThey can get away with less safety buffer and cooling equipment and so at the pack level, they can claw some of that mass energy density back. Not all of it, but combined with other advantages, they're quite viable for EVs, and no brainer for stationary storage.
- caf 5y agoThe CATL LFP batteries Tesla has been using already have only gone in the SR+ model, because they couldn't fit enough for the necessary range in the LR and P models, so in practice they do seem to use more space. As far as I know they're not prismatic, they're using the same form factor as the NCA and NMC cells in those models.
- sudosysgen 5y agoThe article seems to say that these are the BYD Blade batteries so it would be prismatic, unless the article is wrong
- caf 5y agoI'm not sure it actually says that - it says that Tesla has signed a deal for BYD LFP batteries, and it says that BYD blade battery packs are energy dense, but it doesn't actually link those two and say "Tesla has signed a deal for BYD blade battery packs". One of the linked articles does report earlier rumours around Tesla using blade battery packs from BYD, but then also has quotes from BYD saying "we never said that".
- cbo100 5y agoThe CATL LFP are prismatic. https://insideevs.com/news/542064/tesla-model3-lfp-battery-pack/ https://insideevs.com/news/542064/tesla-model3-lfp-battery-p...
- jacquesm 5y agoThat saves a ton of space, and if these don't have any cooling/heating requirements that savings will translate into a more compact pack which may offset some of the losses from the reduced density, as well as weight savings for coolant, coolant loops and pump.
- caf 5y agoThey are definitely heated at least in the Teslas, they don't perform well enough when cold.
- elihu 5y ago> This is somewhat mitigated by the fact that LiFePO4 handles 100% charges and 100% discharge I don't think that's quite true. LFP cells have a minimum voltage; they may survive being discharged to zero, but it probably isn't a good idea for long-term longevity. (I'm currently working on an EV conversion that uses LFP cells, but I haven't actually done durability testing or anything like that, I'm just going by what people recommend.) Lithium ion and LFP batteries though don't have voltages that are linear with capacity; on an LFP once you're below 2.2 volts or so there's not much left. I do agree though that LFP cells are pretty amazing if you're a car manufacturer that wants to make a reasonably priced mass-market EV. I think in the near term (i.e. until there's some cheaper/better substitute), they could take over the non-luxury-car EV market and allow the rest of the world outside of China to start seeing pretty good EVs that are price competitive with equivalent ICE vehicles.
- sudosysgen 5y agoThat's not quite what 100% discharge usually refers. 100% discharge means from the maximum charge voltage to the minimum discharge voltage. That corresponds to, normally, using up the rated capacity of the cell. On lithium batteries you'd normally only use 80% of the rated capacity if you want to maintain durability.
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- jacquesm 5y agoExactly, depending on the make/model that's either 3.0V, 2.8V or 2.5V lowest discharge limit. If you go under that you basically can not longer trust the cell integrity and should dispose of it (no matter what miracle workers on the web say, the copper in the cell will have gone into solution and it can be deposited anywhere at all, but never again in the same spot where it was supposed to be so you are essentially the proud owner of an incendiary with a random length fuse...).
- elihu 5y agoAh, that makes sense. I guess it's kind of arbitrary (I mean, you could just call 80% full "100%" if that's all you'd use in practice) but it does seem quite useful if the "full" voltage is generally agreed to be in a narrow range and not have a wide range of maximum values depending on whether you care more about absolute capacity or longevity.
- jacquesm 5y agoThe annoying bit here is that the LiFePO4 advantages only really start to pay off by the time a vehicle hits the secondary market.
- ethagknight 5y agoBut the first buyer wins with the improved resale value!