Episode 20 of the Modern Chemistry podcast features Nigel Taylor. Nigel is the founder of www.batterydesign.net – ‘Designed by battery engineers for battery engineers’. Nigel frequently posts updates and useful information on the state of EV batteries through batterydesign.net and his related social media channels. Prior to founding batterydesign.net, Nigel has gained over thirty years of experience in the automotive industry with companies such as Jaguar Land Rover, and Rover Group, more recently concentrating on low carbon and electric vehicles. ***UPDATE TO THE CONTENT IN THE PODCAST – Nigel would like to note that the 400 kWh per kWh required to manufacture a battery is a slightly out-of-date figure. Currently, it is closer to 50-150 kWh per kWh of battery power.***
Terms used
If you’re not familiar with some of the terms used in this discussion – some key ones are described here for your reference:
Nigel also mentions the Munro Tesla teardown – you can find that video here - https://www.youtube.com/watch?v=LeZzEg3GIcg
As well as www.batterydesign.net, Nigel is online at https://www.linkedin.com/in/nigel-taylor-2131964/
Our theme music is "Wholesome" by Kevin MacLeod (https://incompetech.com)
Music from https://filmmusic.io
License: CC BY (http://creativecommons.org/licenses/by/4.0/)
Connect with me (Paul) at https://www.linkedin.com/in/paulorange/
H.E.L. group can be found at www.helgroup.com online,
on LinkedIn at https://www.linkedin.com/company/hel-group/
on Twitter, we're @hel_group, https://twitter.com/hel_group
or search for us on Facebook
Please note, this transcript has been provided by rev.com and it has not been reviewed or edited.
Paul Orange (00:09):
Hello and welcome to the Modern Chemistry Podcast with your host Paul Orange.
(00:14):
Hello and welcome to episode number 20 of the Modern Chemistry Podcast. I'm your host, Paul Orange. Today we're talking to Nigel Taylor and Nigel is probably most easily found at batterydesign.net. That gives you a little bit of a hint of what we're talking about today. It's all things electric vehicle battery related. During the conversation, Nigel and I touch upon the interdisciplinary nature of designing safe vehicle batteries. We also talk a lot about the development and where the future is going and some of the challenges that we see today. But I think, if you listen closely, you'll hear that they're more about the opportunities we have for developing the batteries and developing the infrastructure around battery usage. And it's not just for electric vehicles, it's for other heavy draw applications such as energy storage in our homes or even as supplements to our national grid supplies. And at a time when energy supply and demand is a big question, these are interesting topics for us to deal with.
(01:19):
One of the things you'll hear, you'll say quite frequently is what a complex or interesting challenge some of these attributes are. And I think that really is the worst way to think about this. It's a complex system and we're trying to understand it. Chemistry is part of it, so are a lot of other science and engineering disciplines to make car batteries work. So I'll hand over to the discussion right now and I'll be back at the end to say goodbye.
(01:44):
So welcome to this edition of the Modern Chemistry Podcast. This episode I'm delighted to be joined by Nigel Taylor from batterydesign.net. Nigel, welcome to the show.
Nigel Taylor (01:55):
Oh, Thanks Paul. Thanks for inviting me. It's great to be on here. Yeah, very pleased to be on the chemistry program. I'm a physicist by background but that's all the better.
Paul Orange (02:06):
I don't think we'll hold it against you. We've had biologists on here before as well. Well, there's a couple reasons I really wanted to have you on the show. The first one was, I have to admit, batterydesign.net I find incredibly useful and you're very active on social media. There's a lot of really good information coming out. So I'm just going to encourage anybody who's battery curious should subscribe. The other one is that the tagline you have, which is from "chemistry to pack". And that's really what this show is about. It's how does chemistry influence modern life? And I know you focus a lot on battery design for electric vehicles in particular. And before we started up today, you sent me an email and you said, "There's a little bit of a difference between a battery you might think of in your domestic environment and in an electric vehicle." And maybe we could start there and explore some of those differences.
Nigel Taylor (02:57):
And I think that's quite an interesting one. If you look at your mobile phone, you keep your mobile phone probably for two years. Most people they'll recycle it and want something new every two years. A car battery we're looking at 10 to 15 years. So we've gone five to eight times the life lifespan of that battery. In the mobile phone we're discharging it in around about 10 hours. So it's discharge rate, to us would be a C rate of C over 10. That's what battery design is talking, is discharge rate. So it's a C over 10. So you're discharging 10 hours. A car battery could be discharged in two hours. Probably a good driving on the motorway you'll discharge it most of the way down in two hours. In a peak you might discharge it in 20 minutes. Put it on a racetrack, it's probably going to be about 20 minutes.
(03:42):
So the rate we discharge it, and we charge it so different to what we see as the mobile phone and we've got a LIM five to eight times longer. But then also your mobile phone, you keep close to you or you keep it in your office with you. It's room temperature/body temperature. You get in your car and it's minus 20 outside, you expect to be able to drive away. You don't expect it to say, "Actually, I just want to warm up," and maybe that will be an hour. So it's got to operate and be able to discharge at minus 20.
(04:10):
If we take it to a hot climate, it's still really got to be operating plus 60. It's had a hard life, it's been down the motorway in a 40 degrees C ambient, the temperature will be up at 60 degrees C. So all of that and put that together and then go, "Oh by the way, your warranty period is 10 years and 150,000 or plus miles," which all the companies have extended the warranty. Because I think that's the one thing in terms about electric vehicle adoption, you're really concerned about how long's it going to live? Is the battery any good? Am I buying a secondhand product that maybe only lasts two years?
(04:44):
So that whole thing of a warranty that's eight years, 10 years and it's the lifetime of the car that's beyond I would normally perhaps have a petrol engine car for, that makes you feel better and that gives you confidence that they designed it to a certain level. So that whole thing of this throwaway society for a mobile phone versus the keeping of a very complex battery in a car, it's a very different beast. And I think also that's why I put "chemistry to pack". Because when you look at it, when I think in terms of designing battery packs, there's five core elements that always go back to and check myself against. And that's any level of physical level within the pack, whether it's a cell level or module level or complete pack level and that's electrical, thermal, mechanical, safety and control.
(05:27):
Those five elements we always go and just check and go, "Are we okay? Have we got anywhere where we might have resistance issues on the electrical side? Might we have a possible short?" All of those things coming on the electrical. On the thermal, in your mobile phone you've got one cell to worry about. If you go to your Tesla, you could have 6,000 cells in the big Tesla. If one of those cells is not behaving very well and is a bit cold or is a bit tired, your whole pack behaves like that one cell. So we've got to design a pack that's not just we keep all of them roughly about right. We've got to keep all of them very happy.
(05:58):
All of the 6,000 cells have got to be the same, they've got to have the same temperature. They really want to be charged and discharged the same. So they need to be electrically connected to the system the same. That all needs to be very even in order that we can give you that 10 year plus lifetime and all of that performance. So that's the whole challenge of it and I think that's where it's been quite difficult. You look at your remote control on your tele and it's two cells in there. You look in a Tesla and it's 6,000 cells or around that sort of number. That whole thing of that level of complexity of what we're dealing with is so different. And, again, with the iPhone, you have a warning when you get on a flight, "Please don't drop it down the side of your chair." Because if your chair moves or if someone stamps on it and it gets crushed, it's likely to catch fire or get very hot, at least.
(06:42):
A car battery pack, we have to design it that you can have a crash and it's HV safe. No one can stick their finger into it and electrocute themselves. But also it can't thermally go wrong. So if goes into thermal runaway, we have to know that and give enough time, five minutes, for the passengers to get safely away from that car. So that level of knowing how the pack's design and control system and also the safety elements around it are a completely different level to what you experience with the one cell in your mobile phone. And it makes it tough, but it also makes it really interesting because we need chemists, we need mechanical engineers to design the structure.
(07:20):
These packs are 500 kilograms plus. The car is designed around the pack now. It's a big heavy element. That's got to be taken into account. So all of that in terms of the chemistry, the mechanics, the electrical design, because we've got to be careful of arcing, we're at 400 plus volts on most of the packs and we're looking at taking that up to 800 volts, all of that becomes difficult because one of the cells goes wrong, we could put a very conductive gas into that pack and all of a sudden we see arcing. So there's a whole load of things to think about just when it's all going nice and safe working well.
(07:56):
And then on top of that we've got a control system. The control engineers have also got to have a good understanding of the chemistry or at least listen to the chemists and understand when they're perhaps pushing the cells or asking too much of them, or they're cycling them in such a way that they become different. There might be slight differences in those cells that when you cycle them lots of times those differences increase. And that's always a concern for us. Which is why, when you look at designing the pack and you're testing the cells, you'll be testing a thousand cells individually and you'll be cycling them for a long time, probably for 18 months, to get enough data to understand the slight changes you get when you cycle them in slightly different ways.
(08:35):
And all of that data will come back into the modeling world and then you'll start going, "Well, what if my pack has got the sun on one side and it's sat cold on the other? Is it going to start seeing a different temperature across the pack and can I deal with that with the cooler system I've got installed?" All of those sort of things are taken into account. And that's what I think makes it difficult, as I said, and really interesting by the sheer number of skills. There aren't many fields where you put so many people sat next to each other working on the same product. And I think that's the exciting part, really exciting.
Paul Orange (09:08):
A lot of directions we could go a lot to unpick there, but maybe just simplistically try, if you could, paint a picture for the listeners. So we talk about the fact that an electric vehicle, I'm sure we're going to pick on Tesla a lot; other electric vehicles are available. You take your battery for your electric vehicle and it's not just like a bigger version of a AA battery or the battery on your cell phone, is it? It's fundamentally different concepts. So could you maybe explain that the best way you can?
Nigel Taylor (09:34):
Yeah, so let's just look at the connection of it first. So as we said, we've got 6,000 cells but they're not just 6,000 cells shoved in a box and that's it. We've got to connect those all together electrically. So let's think about how we connect them together electrically. In a car, we're pulling a lot of power out of the car. Again, in a normal car we're probably pulling our two to 300 horsepower we want in these cars and that will be 200 plus kilowatts we're pulling from the car. You can't run that at 3.6 volts in ohm or 4.2 volts peak. That would just be a silly current. And as we all know, if you look at the actual heating and the losses, it's I squared R. So it's the current times the square times the resistance. So you can't run low voltages and very high currents.
(10:17):
So we end up pushing the voltage right up. We want to go up to nominally probably around about 400 volts, keep it 450. You've got to operate across the window. So a lithium ion cell will operate from 4.2 volts maximum down to around about three volts at the bottom end. If [inaudible 00:10:34] really hard, will drop down to 2.5 volts for a brief time, maybe 10 seconds, will drop down to 2.5 under high loads. So typically we are running 4.2 volts down to three volts. 3.6 volts about the nominal voltage of the cell. If we look at that, what we've got is a 3.6 volts out.
(10:52):
So we want to put lots of them together in series. So we connect the positive to the negative, from the positive to the next one, to the negative to the next. And we keep going up and we end up with around about a hundred of those in series. And that gives us our nominal 360 volts up to 420 volts peak. And, as I said, down to absolute minimum, 250 volts when you're driving very, very hard and demanding a lot of power, so that gives you sort of the voltage range.
(11:20):
But then of course we want energy. If we just took that normally we'd have a hundred in series, we'd have a five amp hour cells, so it would be 360 volts times five amp hours. It would be, off the top of my head if I can do the maths, it's 1800 watt hours. It's 1.8 kilowatt hours. That would get you sort of 10 kilometers. That's not very far. So I'm now going to connect them in parallel. But actually what we have to do is connect them in parallel first. In a Tesla, and this is just off the top of my head the numbers, but we'd put 60 of those cells connected in parallel. So we connect the positive to the positive negative to negative on a group of cells, the 60 of them connected in parallel.
(12:00):
And then we have those groups, a hundred of those groups connected in series. So now we've got a series in parallel connection of cells and we'd call that 100S 60P. If you look at in simple terms it will be 60 times, let's say a five amp hour cell. So it'd be a 300 amp hour block of cells and then we'd be 360 volts in terms of the nominal voltage. So the capacity of the pack would be 360 times 300. Off the top of my head that's roughly a hundred kilowatt hours. It's somewhere around that number. That gives you the sort of sizing in how we scale and just get the energy and the power for the pack.
(12:35):
But of course, as I said, now we've got blocks of cells in series. They've all got to be connected the same. They need to see the same resistance, they need to have the same cooling connection. When they generate heat, we want to keep them all within the same temperature. And across that pack, the design of our cooling system has got to be good enough that we can keep any cells within about two degrees C of any other cell. That's quite challenging. We can let that grow a bit when we're driving it hard, but we really want to get back to that two degrees C difference. Because start getting large temperature differences, especially across a parallel group of cells, then what you start seeing is if you pull a high current, you'll get different discharges and pull downs on each of those cells.
(13:15):
When you relax that back to their just open circuit voltage, they will all start trying to equalize and you'll start seeing very high, what we call ringback currents. So you'll see the cell that's now perhaps not been discharged as hard will start actually trying to charge the other cells that it's in parallel with. And so you'll start see high currents being shunted around these circuits internally within these circuits. So we have to be careful that we keep it all the same. So those cells mechanically then, we're going to connect them all together. We're going to electrically connect them all together and we're going to cool them all the same.
(13:46):
We've also got to make sure that they don't vibrate apart. We're 10 years down a road. So if you look at the vibration that you see on the car, it's quite high. So you've got to be able to survive all that vibration on the car as well. That's a challenge. But then also you've got to know what the temperature is of all those cells and you need to know the voltages of all those cells. If their capacity between them changes too much, that will limit the overall capacity of the pack that you can use.
(14:12):
So then we'll do what we call balancing. So we'll put slight discharge and we'll put a resistance across the very high cells to bring them back down and just lose some of the energy out them so that we can bring them all equal to the other cells. So that, when we charge them all up, we can get to the max voltage. The same for all of the cells. And those voltage limits we have to be very careful of and very strict with. 4.2 volts and you'll see it defined on the specification sheets, that's it, you stop. It doesn't matter whether some of the cells may be down at 3.9 volts, you have to stop at 4.2. You can't carry on charging and just keep going up there because those cells that are at 4.2 or pushed higher than 4.2 volts will start getting hot and then you can go into what we call a thermal runaway of a cell, so it could catch fire.
(14:55):
And that's a challenge then because if that one catches fire, it's highly likely to propagate through the pack and that thermal runaway at pack level is something that we have to design for to either stop it, which is the best scenario, or to manage it such that we can detect it and we can warn the driver and ensure that the driver can get safely away from the car in the time that we've got in the five minutes. And that's a challenge. When the cell does go wrong, you get a lot of gas, you get a lot of heat, and it can be quite a difficult situation to handle. So that whole challenge is all going on inside that pack.
Paul Orange (15:29):
Yeah, and you mentioned cooling as well. So this is something that many people don't realize that, even relatively small batteries might have some sort of cooling infrastructure or release put in them, but all these cells that you're talking about in the electric vehicle, they're not just, as you say, connected together and stuck in a plastic box with a big plus and minus output on it. There's a lot more going on inside the overall container isn't there, inside the pack?
Nigel Taylor (15:54):
Yeah, there is. So that's it. Mechanically you are holding them, so you're stopping them moving, because you've got to ensure that your electrical connections stay connected to all the cells. You've got to decide where you want to put your temperature sensors. If we've got a pack with 6,000 cells in, I don't really want 6,000 temperature sensors in there, because that's an awful lot of channels to try and do anything with that information. It's a lot of cost and it's a lot of complexity that I don't need. So what you tend to do is you'll probably put two temperature sensors on each of those parallel sets of 60 cells, but then you've got to decide which of the two you put the sensors on. Where do I put those sensors to try and get the best estimation of the pack temperature? Because what I'm trying to do with my control system is say, "Where is it hot? Where is it cold? Could I change my flow? Could I change my flow rate?"
(16:38):
I can't do much. All I can change is my flow rate and perhaps my inlet and outlet temperatures a bit. I can change my inlet temperature by asking for colder fluid or asking for it not quite so cold. So there's only a few parameters I can play with. Or I have to tell the car that they can't have the power they want. And then the car has to tell the driver, so you are into this chain effect of saying, "Look, I can't deliver the 300 horsepower you asked for. At the moment I'm limited to 200 and you're going to have to live with that." The driver will get a warning that he'll start feeling the car being limited at a certain point and we'd rather do that than get to the point where we have to do something more dramatic like pull the contacters or just literally open the contacts and say, "You've got no more battery system in there. You've got no power at all."So we've got to get a cooling system that we get the heat out of the cell so it's firmly connected but electrically isolated. This is a pack at 400 volts. I can't have a cooling system that connects to all of the cells because either I short the cells out with the plates of the actual physical system that the cooling fluid's running through, or I get electrolysis in the actual fluid itself. So I've got to electrically isolate it and yet thermally connect it. So I end up with a challenge there that often you'll see, and most of the cooling packs you'll look in, a bit like you see in the old refrigerators with the aluminum panels with the ribbing in and you see the coolant flows through the middle of it. You'll see lots of those across the pack. Now what you have to do is you end up putting a coating on there to give you electrical isolation and then you end up with thermal interface material between the sal and the coolant plate and that thermal interface material will have a thermal conductivity that is rubbish.
(18:19):
Most of those, they're silicon based compounds maybe with a bit of graphite or a bit of metal particles in there to give you some conductivity. But the numbers are very, very poor conductors. They're two watts per meter square [inaudible 00:18:32]. They're really, really bad numbers. So what you end up with is trying to make them very thin. So you end up with a very thin amount of that material to connect the cell to the coolant plate. But mechanically, they're sort of isolated on the silicon system. But again, you don't want that to vibrate free. You don't want it to peel off over the lifetime of the car. Again, one side or some of these cells start unpeeling, then they're going to start running hotter. And then I'm going to start aging parts of the pack before other parts age. And, as I said, the weaker cell will limit everything I do.So one cell in my 6,000 becomes very weak, that's how good my pack is. I can't exploit all the energy in the other cells. So that's my fundamental limitation. So I'm trying to keep them really connected to these coolant plates all the same. I want them all connected the same and I want them all connected the same over the lifetime of the pack as well. So I have to look at the aging of those materials. How do they age? How do they mix with the other materials in the packs? Are they chemically compatible with the cells? Are they chemically compatible with the coolant plates? Are they chemically compatible with the mechanical system that holds the cells together? All of that is, again, something that you have to look at in your design of your pack and then also your mechanical system that you're holding your cells together on all of it has to be okay up to a certain extent when something goes wrong.
(19:47):
So if you go into a thermal runaway of a cell, the gases coming out will be somewhere between 1000 and 1200 degrees C, it will probably vent, even a small cell will vent, for 30 seconds to a minute. It is quite a lot of energy comes out. What you don't want is your mechanical system, that might be a plastic, holding the cells together, to completely break down because then I've got just a load of loose cells in there. The worst case is they're going to interact. But also I don't want the plastic being part of the combustion. I don't want any more combustible parts in the pack as well. That design has got to really go together. Every element has to work. That's challenging.
Paul Orange (20:21):
And at the moment a lot of these battery packs for the electric vehicles, they're built once and intended to be in the car for life. You can't change over the cooling system or if you find a dud cell you can't replace it. So it really is important to get this design right in the lifetime and the performance sorted out early on. I think probably the exception is, I know you're kind of looking at me a little bit [inaudible 00:20:45], thing is I've seen some designs where rather than charging up a car, you drive into a replacement station so it takes the discharge battery out, puts a new one in and then charges the battery up for the next user. So that design of that vehicle is inherently more open to replacing the battery.
Nigel Taylor (21:09):
It's been a modular approach when it all started back in the early 2000s, there was a lot of cars with the modular based approach where they had perhaps 30 or 40 of these modules in, which was smaller collections of cells assembled into the pack and onto coolant plates and then that would all be packaged up and put in the car. As there's been a drive for cost, cost down, part complexity, take all the parts out you can. That's actually driven probably the wrong way for recycling and repair because it's meant that people have gone, "Well, actually let's have less modules." The Tesla before the last one, there were four massive modules in there. They couldn't really be taken out and repaired quite frankly. If anything went wrong with it was a new pack. The latest version of the Tesla and some of the Chinese companies, BYD and people are doing, you can't take those packs apart.
(21:59):
The latest Model 3, there's so much foam and resin in there that effectively the whole pack is built as a structural element and that's it. One cell goes wrong, it's the end of the pack. Now I must admit, I'm like you, I'm not quite sure how that's going to work with recycling. Well, it doesn't work with repair, it's complete battery pack swap and change. In recycling and reuse, I think that also becomes a problem. We've got a 500 kilogram battery pack, it's taken an awful lot of energy to make that battery and it's over 400 kilowatt hours of energy goes into one kilowatt hour of battery. The total life cycle analysis energy. What it means is, at some point, I'm going to just use up all the planet's resources. Effectively making packs and shoving them in landfill because I can't do anything else with them other than perhaps chop them up and try and extract anything that is worthwhile.
(22:56):
And that's where we are at the moment. They tend to be chopped up and they remove the cobalt of the nickel or anything that's valuable in there like the copper maybe. So it would be copper, cobalt and nickel removed from it. I think we need to think about longer term and we do it now with lead acid batteries. So if you look at lead acid, the lead is actually recovered. Although it's not a very nice technology though in term materials, they are actually on a fairly good circular economy that actually means they're reused. And we need to get there with lithium batteries or wherever we go with chemistry. We've got to get to the point where we're able to take 95% of everything that's in that battery pack and recycle it back into raw materials that are good enough to go back in another battery pack. Not downgrade it, because a lot of it at the moment ends up as black mass and ends up in your roads as road fill or whatever else.
(23:45):
You really want it as black mass that I can actually pull the chemistry out of, and I'm going to put it all back and I'm going to put it all back into the next pack I build. And now some of that might come about by legislation. I think some of it will come about by the fact that we don't know where to go and get those materials. And you can see it already. Some of the Volkswagens, one of those other companies, are going, "Well, where do we get the materials?" Well, one way is to actually buy back the old packs and find a proper way of recycling each of the materials so I can put them back into my system at the front end.
(24:15):
Otherwise, cobalt, some of the other elements, the mining rights are owned by Chinese companies or Chinese government. So it's quite an interesting play that's happening there and I think it'll be interesting how that goes over the next few years. It might be you just have to do it, because you can't get it any other way than recycle it.
Paul Orange (24:36):
I mean I think you're right. I think economies often drive the innovation in the technology for recycling and reusing things. If anybody is listening thinks that we're over egging it, take your batteries down to your local recycling center and they recycle it. I mean, find a video online of somebody taking apart an electric vehicle battery pack and you'll be surprised how much gunk there is in there. It's not just the batteries.
(25:00):
One of the things that a lot of people are talking about now, in particular looking at electric vehicle batteries, is second life because we're electric vehicles have been on the road long enough now where you're starting to get to that point where the battery packs are no really longer fit for purpose as driving a car but useful in other applications. Have you seen any really exciting applications coming out of that second life approach? It sounds very attractive.
Nigel Taylor (25:29):
I think it sounds attractive. There's some really interesting stuff going on with vehicle to grid connections and I think about that first. Connect your car into your house and actually it could supply power rather than just charge it up. It could supply power to your house and protect you against brownouts. So I think that's a prior thing to even perhaps second life of using it in a container and doing other stuff with it. There are people who've taken battery packs and put them together in containers and then use those to give you fast charge stations. Maybe where you can't get a very good electrical connection to the grid. You can charge those batteries up and then a few cars can turn up and do a very fast charge to get them moving again. So there's interesting ways of using them to do that charging or protect the grid or use them in local communities.
(26:16):
I think it's Ford who are probably going to be one of the first to do it with their F-150 pickup truck, the new F-150 Lightning. It's got vehicle-to-vehicle connection on it. If your friend breaks down, you can turn up and you can put a lead between the two cars and you can give him some of your charge to get him on his way again. That's quite an interesting way of trying to solve some of that buffering everything. I think the whole reuse, the problem I have with it is... And I think that's part of what we were talking about with the complexity of the pack, to make it economical, I probably can't afford to take the pack completely apart and take all the cells apart and reconfigure them, because I'd rather do it in a way that's cheap enough.
(26:54):
I think if anybody watches the latest Munro, the guy's taking apart the latest Tesla, you'll see they have to invent methods to take it apart because it's so difficult. And I think that's going to be a problem that we need to think about. Because I think that, as you say, how do we use the batteries for the full term of their usable life? It is quite difficult. The other thing is the economics. Now maybe the hiking price of electricity is going to help that, but you have to work out, well a battery is going to live, a roundabout, just off the top of my head, a good battery from new will do about 3000 cycles and before it's down to about 70% state of health. In a car application, you don't really want to run below that. I mean, they will but that tends to be where the warranty runs out and the system is sort of designed to.
(27:42):
But if we looked at a hundred kilowatt hour pack and we had 10 pence per kilowatt hour, which I know we're a lot more that now, we're now at 30 pence a kilowatt hour, roughly. But at 10 pence kilowatt hour, that's going to cost us £10. There's £10 worth of energy in it. If I can make 10% of that, I'm probably doing very well on a buying at one rate and selling another. That's where I think it's the reuse. That second life, you've got to think about, well, if I'm only making two pence per kilowatt hour or I'm buying it and charging up at night time and then supplying back to the grid during the day, it's very difficult I think to make money off that and make that commercially viable system. And that's a question whether I could use those second repurposed batteries for my own home, where I've got solar panels that would charge it when I'm at work, and then I can use that energy in the evening when I'm at home. That's a possible application.
(28:29):
I think the concern is I'm taking a battery pack that's already perhaps had a hard life, how do I know that state of health and the quality of those cells? And then I've got to engineer them into another safe application and make sure that they don't go wrong. And I think there's been quite a bit of concern over doing that and that's why people have tended to go for brand new cells and put brand new cells into those packs because they know where they are, they can engineer it, they can sign them off, they can be happy with it.
(28:58):
I think as we get better with estimating the state of health and where those cells really are in terms of their lifetime, whether they're going to go wrong and what we say is a knee point; once they get below 70% state of health, at some point they go off a cliff age in terms of their health. You don't really want to do a lot of work engineering them into a second life only to find out that two months down the line they all just collapse in terms of their capacity and their ability to charge and discharge.
(29:24):
So I think there's an interesting thing of second life, can we do it? But it really is down to a commercial, is it worthwhile? Compared to how much or the value of them in that second life? So it's either going to be really easy where I just take the pack and I take the whole pack and shove it in a container, connect it up, use exactly the same control system, no changes and I know where it is and it doesn't matter. And I think there's a bit of a dilemma there. Maybe electricity costs going up, a lot more of these ideas I think will commercially become viable again. And we'll see some other exciting applications I think. Quite soon see some exciting applications of that vehicle to grid as well. We start seeing difficulties with the grid in terms of brownouts and that sort of thing. That's going to become quite valuable to people I think, that you could keep your house running.
Paul Orange (30:10):
One of the things that I've spoken about with a couple of people is, and you've mentioned safety already, if you're driving along and it looks like a battery's at that point of, "Okay I'm going to fail. I'm give you five minutes warning to pull over, get out the car and be a safe distance away." That's one thing. It is very different though if you've got a battery pack in your house because if that does start to degrade, there is no five minute warning. You're not going to be able to pull it off the wall and throw outside. You've got a house fire going on there. Which is why the safety is so important. And you mentioned the recent tear down of the new Tesla pack, right? It's one of those things to think about is mechanical safety as well has got to be traded off a lot, because cars crash. Stupid things, like you get stones flying up from the wheels. So where does that sit into this whole design process?
Nigel Taylor (30:58):
When you look at your whole safety concept, you look at the whole system and it comes back to what I said with the five things earlier. The electrical, thermal, mechanical, safety and control. But then you also look through all of the layers of the system. So if I look at the cell level, in terms of my safety, as I said, I don't want to go over 4.2 volts. So that means I measure every single cell in the string. So I do a hundred voltage measurements and I ensure that I do not go over the 4.2 volts on any of those strings of cells that are put together in parallel. Whether it's one cell or 60 cells, they're not allowed to go over the 4.2 volts. That's one level of safety that I've got there. I've also, within each cell, and it depends on the cell, some have got fuses in. Effectively, a vent in, some haven't. And some have got an electrical disconnect in there, so if they go over temperature, that causes a rise in pressure and that then electrically disconnects it.
(31:54):
So depending on the cells and what I'm doing, I have to think about that within my design. I will then have, if I look at my control system mount, I will have the ability to switch it on and off. So I can electrically disconnect the pack from whatever it's connected to, whether it's the grid, in your house or the car. I can actually pull the contactors and disconnect. And I can do that with a system that will allow me to reconnect it or I can do it with what we call a pyrofuse. So we can actually just fire a fuse and that will be it. It's disconnected. And depending on how the system's designed, on some designs we will put a pyrofuse in there so that we can actually just disconnect it if anything goes wrong.
(32:34):
But then you've also got, on top of that, normal fuses. So you will have 150 amp or 1000 amp fuse in there to protect it from very high currents due to a short or anything else. It's a mechanical system that will blow. But then on top of that you have all of the things that we test against. So in the design and test of a battery pack, cool battery pack will take 18 months to really four years to design and test so that we can make it robust enough to go in a car. Because we're going to test all of those, we're going to put a nail through it, or we're going to heat up a cell or we're going to overcharge it and prove that we've got a system that will allow that cell to, if it does go wrong, it can vent, where does the gas go? Can we get the gas safely out of the battery pack and not end up with a high pressure problem?
(33:24):
And we'll check that under all of the operating conditions to make sure that's safe. So there's a whole load of layers of safety and protection that we've put on there to try and check that through. And we'll have looked through a fault diagram to see what could go wrong and whether we can stop this problem happening at two points. Either with control or with control plus a mechanical or an electrical system on top of that, that will give us another point at which we can stop that failure mechanism. You will see in battery pack designs, you'll look at it and go, "Why does it appear that the busbar has been thinned down at that point?" And it might be that's a way of putting a fuse into a local group of cells.
(34:04):
And you'll see some cells they've been thinned down sometimes because that's just taking weight out and we don't need to busbar size. But otherwise it will be, "Actually, we just thinned it down because we want to create a fuse there that, if it does go wrong, that will just disconnect that part of the pack." So things like that. And then, as I said, the gases, in terms of how they flow within the pack and then out, there will be a lot of work done in modeling. So full 3D CFD models are run on how the cells fail and how the gases escape from the packs. Normally [inaudible 00:34:34] burst disc. We also look at what happens if the cooler system has a leak and leaks into the pack. Is it okay that, actually, we can have that amount of liquids sloshing around in the bottom without having an isolation problem or a electrical problem? Or do we have to actually detect it and then allow it to be released?
(34:50):
So there's different levels and strategies depending on the pack design. So all of that's in there as well. And I think you probably need to take someone through that safety and the walkthrough that we do on everything in terms of, because it's high voltage, are we safe? And, again, when you switch your car on you think, "Oh, that just turns it on and I can drive away." The battery pack has gone, "Am I okay? Am I at the right temperature? Are all the cells looking at the right voltage? Right. Okay. But can I just do a check and I'll check that I'm electrically isolated from the ground." So it'll check that it's got a level of isolation between the battery pack and the rest of the system. And it will do that.
(35:29):
And then it will do a handshake across the system before it then goes, "Right, I will now be closing the contact," and effectively, it'll ramp that voltage up and close the contactors. You've got a motor and a controller with some big capacitors there. If I just shut the contactors, I'll probably cause a problem because I'm going from zero volts to 400 volts with a lot of current. So I will bring that voltage up carefully and then I'll close the contactors. So things like that are all happening between you hitting the button and you driving away because it's going, "Right, am I okay?" And then it's constantly doing a handshake going, "How much charge can you accept at this moment? How much power can you give out?" It will do that hundreds of times a second. Talking to the vehicle control system and saying, "Right, you can have this. You can't do this." Or, "And I'm okay at the moment and this is my total power window."
(36:15):
The control system on the battery will be effectively publishing all of that data to the car the whole time. And the same way it's being charged up. It will be talking and doing a handshake with the charger. Before you plug your plug in, it will then go, "Am I okay? I will do a handshake. I'll check that I can talk to you, I'll check that you're at the right voltage and that everything's going on I can match it. Right, now I'll close the contact." And it will, again, be thinking about the whole cooling system or the pack, whether it has to call it, whether it needs the air conditioning system on. But all of that has to come into the design of the overall electrical system on the pack and the car. That's one thing we have to think about. What happens, not just when the car's driving normally, but also when it's sat there or sat there charging. What's it going to do?
(37:00):
How often does it wake up and go, "Am I okay?" What interlocks have I got to stop you driving away when you've got the charge lead in your car? Because we don't want you driving off in that condition. So there's layers of safety over the top of your car as well as within your battery pack. And it's not stupid behavior, but we all forget. So those layers happen. Everything, both mechanical, thermal layers, everything's going on to try and get to that point.
(37:25):
Going right the way back to that cooling system we talked at the beginning, when we're testing the packs early on, we will cover the pack in thermocouples to make sure that our estimation of these perhaps only four or 12 or 20 thermocouples that are normally in the pack during normal operation are a good indication of the temperature measurements across the whole pack. So we'll put a sensor on every single cell and if it's 6,000 cells, we'll instrument every single one to make sure that we're within a certain criteria and drive that pack through all of the possible drive cycles and all the charging cycles to say, "Are we a good match?" That's quite a challenge.
Paul Orange (37:59):
And like you said, there's 18 months to four years to develop a pack and this is the kind of stuff we got to go through. Nigel, I'm aware of time and you've been very generous with yours today. Maybe one final question just to finish up with, we've heard about a lot of the challenges and the things that we have to do make battery packs working the way we need to for electric vehicles. What's coming over the horizon that makes you excited about battery packs and what's it going to give electric vehicle drivers? Is it going to give them quicker charge times? Longer ranges? Better safety? Improve all the above? What are you excited about?
Nigel Taylor (38:33):
We've got faster charging coming. At the moment we're all used to perhaps 50 or a hundred kilowatt charge. You've got some exotic cars going to 350 kilowatt charging. That's going to come to the masses. It's all going to happen for all of us. I think the bit we want to see, we've got cars that work now. With the energy densities and power densities we can make something that's very credible as a car. They're really good cars. What we want to see and what we're seeing coming along is better control systems. They have a better idea of how to manage the pack. They have a better idea of how to get the most out of those packs. We've got data over the air, so they're all going and sending data back up to the cloud, you're seeing it on your phones, you're seeing how healthy your pack is. But we're starting to see now where actually, they're going to start changing how your car is managed based on your use of it to extend the life of the battery pack.
(39:18):
We can optimize the control of your pack now in the cloud and we can send a control system back and change some of those parameters in the control system. Make it more tailored to you to give you the best range, or give the best power or give you the best experience when you first jump in on a cold morning. So all of those things will start to come. Also, from that, you'll get more confidence. I've worked in electric vehicles since 2008 when we designed the first research car, but you've still got that little nervousness. What happens at five years? What happens at eight years? Do I want an eight year old car? We've got to get to the point where that's the norm. You don't worry about that. That's coming with better control systems, as I said. Better chemistries that are more robust. They will charge faster without any damage.
Paul Orange (40:02):
Yeah.
Nigel Taylor (40:03):
We've seen niobium, trace elements, being put into some of these cells to make them more robust. That's starting to come. And I think also that whole thing of safety is not a question of you get five minutes. What we'd really like is there such... That's it. I'd like it to feel like it's my remote for my tele. I don't worry about that going up. Why should I worry about my car? Look at the amount of money, the amount of talent going into battery research. Everything, from the chemists, physics, mechanical engineers. It's an exciting world, because you can cross so many of those different fields in one design. I think that's, for younger people starting off, it's a good area to get into. Go and work in modeling or in design a battery pack. The range of people you're going to talk to and topics you're going to cover is probably one of the richest fields you're going to have in terms of the whole of the industry.
Paul Orange (40:50):
And it goes from the top to the bottom, right? Formula E is the equivalent of Formula One all the way down to standard car you're going to drive around doing the shopping. There's opportunities across the whole value chain there, isn't there?
Nigel Taylor (41:01):
Yeah. You mentioned Formula E there. With their latest battery packs, they're making a step change in energy density. It's going to feel like an early 1970s Formula One car in terms of performance. That's amazing.
Paul Orange (41:12):
Well, Nigel, thank you very much for joining us on the show today and, look, would really recommend anybody who's listening, interested in finding out more or, more importantly, staying up to date with what's happening, check out batterydesign.net. I will admit I follow them largely on LinkedIn because it just appears in my feed and everything you need is there. Nigel, again, thanks very much for your time. Really appreciate it.
Nigel Taylor (41:33):
Thanks for the time. I've really enjoyed it. It's been great. Yeah, thank you very much, Paul. Cheers.
Paul Orange (41:36):
There we go, that's episode number 20. Thank you for listening all the way through to the end. And, again, let me thank Nigel for his time and his passion on joining us on the show this week. If you're interested in following up on some of the things that Nigel spoke about or seeing how EV battery development is progressing, definitely check out batterydesign.net or subscribe to batterydesign.net or follow Nigel in your social media channels of choice.
(42:05):
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(42:33):
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