Purplemeanie

Afternoon all, I've just uploaded the first progress video on this EV project of mine. The video covers the purchase and road registration as an ICE car.

Hi All, For those of you that can make it, we have our monthly meeting tomorrow, April 9th at 8:00pm (Zoom details are sent by email). Before we get into topics. Can I ask that, if you've haven't, then you all do the following on the new Website: Join the EV Special Interest Group here Follow the News Section here Follow the Forums here You can also subscribe to the EV SIG Calendar and have the meeting dates always on your Phone/Tablet/PC by going to this page and selecting the "Subscribe" drop-down and then "Subscribe to iCalendar Feed" (follow the instructions), best done on a phone/tablet. I'm asking you to do this because in the future these links will enable you to get EV SIG updates as we move away from these emails and LoveAdmin. Tentative Topics for Tuesday: John's EV Project updates Progress has been a bit slow this month as I've been let down (twice!) by my prospective motor and inverter supplier. I'll have the full details on the call. Hopefully see you on Tuesday. The background for the interest group and info about the meetings can be found here: https://www.caterhamlotus7.club/forum/chitchat/announcing-interest-area-electric-vehicles The minutes of the meetings can be found here: https://www.caterhamlotus7.club/blogs/blog/359-electric-vehicles-news/ If you’ve not joined the calls before then in brief the agenda will be: Introductions by new attendees What’s new in the EV world Thoughts on Caterham’s plans for EV Seven Conversions AOB Participation in the meetings is, of course, optional. John

Aft'noon all, JK has twisted my arm to throw my experience of Lithium batteries into the ring here. Firstly, after the second Banner battery died on me in the space of 3 years, I decided I'd go Lithium. I nearly did when the first Banner died but I needed something quick and so just went with what I knew - Banner. But when the second one went, it was time for Lithium. My first purchase (yes there's more than one), was a Varley Li-5. This had been recommended to me so that's what I went with. Specification Model: 7162-0002 Battery Chemistry: LiFePO4 Nominal Voltage: 12.8V Capacity: 5.5Ah Short Circuit Peak Current: 736A Cranking Current*: 335A Dimensions (LxWxH): 99 x 82 x 95mm Weight: 1.1kg Terminals: M6 Female Operating Temperature: -10ºC to +50ºC Storage Temperature: -20ºC to +60ºC Unfortunately after installing it and playing around with mounting options, including buying the Varley Mounting Bracket for the Li-5, it was clear after a few weeks that the Li-5 wasn't up to the job for a 420 2.0L Duratec. Turnover was very sluggish and it didn't take many cranks for the battery to then twist the engine even more slowly. It never actually let me down starting the car, but that was probably only a matter of time. So, I went back to the Demon Tweeks website and had a look around for something bigger. I landed on the VT-900.. here's the specs from the Varley site: Specifications: DMS Part No: 7162-0068 Voltage: 12V Capacity: 16Ah CA:160A CCA:900A Terminals: M6 Female Weight: 2.5kg Dimensions (mm) LxWxH: 175 x 87 x 155 As you can see this has nearly 3 times the cranking current and lights my 420 up like it's been struck by lightning. The engine cranks really quickly and fires immediately. Much much better than the Li-5 and much better than the Banner. The battery has been installed for about 9 months and has held its charge over the winter, even without being on a battery conditioner. To be honest, I think this battery is overkill for a 420, but it certainly seems to do the job, for the moment. And there are as many solutions to this problem as there are cars. 🙂 Mounting I also recently modelled and printed a battery tray so the smaller VT-900 sits in the space that the Banner originally sat in. See pictures below. The battery needed to be located in the centre of the tray, but also needed raising. The 3D print solves that problem in all three dimensions. STEP And STL files attached and linked here... 420 Lithium Battery VT-900 Base v2.step 420 Lithium Battery VT-900 Base v2.stl The mount has been installed for a few months and is working well at the moment.

Some brief notes on discussions: Caterham Cars 2024-02 Webinar with Bob, Simon and Richard (here) General view was that the conversation was rather downbeat, while some thought it was ok to see/hear warts-an-all CC are clearly more negative about EV Seven. And group agreed it looked difficult to come up with a business case for a EV Seven Group discussed Project V and still concerns about whether CC can find the money. There was scepticism that CC can get away with the £100m figure they cite for turning Project V into a production car. Apple pulling out of their EV development and Dyson deciding productionizing their concept would have "bankrupted the company" Electric Classic Cars video on how an EV conversion is registered (here) Agreed this was a good video Emphasised why its important to do conversion in line with R100 testing AND why important to keep above DVLA's Heavily Modified Vehicle points rule threshold JM's videos People didn't have many comments (probably being polite!) JM EV Project JM went over the images from above of proposed gearbox by sharing screen of Fusion 360 models JM mentioned how difficult it's proving to be to find component designers (gearbox, motors etc) who are prepared to work with "man in a shed" operations, even though JM is using a company with good financial history etc to run the project through. JM was looking for people who could give practical experience of gearbox design Steve Perks from Tracksport was mentioned as someone to contact It was suggested that JM go back and think if space planning problem can be solved with simpler solutions. Some agreed, but others thought solution wasn't too bad given space constraints JM showed how he controls CAD packages with SpaceMouse (here) JM said next job is to 3D print the design with real bearings to prove it "works" and can be assembled (its quite possible to design something in CAD that can't actually be put together)

If you're coming a long to the meeting tomorrow then I'm hoping to have a bit of a discussion about my thoughts on epicyclic gear reduction boxes. Here's some images and a video that have been posted to the WhatsApp group... Hopefully see some of you tomorrow. John EV_Gearbox_002_2024-Mar-11_05-45-22PM-000_CustomizedView14920322368_mp4.mp4

For those still following (awake), I've also posted a more in-depth look at this project here: https://purplemeanie.co.uk/index.php/2024/03/06/ptevis-suspension-logger-mini-project/ John

Hi All, we have another Zoom meeting coming up next week. The following text will go out by email and also include the Zoom link ( I don't post the Zoom link here as these posts are public). Topics for Tuesday Caterham Cars February Webinar (see my notes here: John's EV Project updates I released two videos in the past couple of weeks. You can find them linked in this post: I also made a forum post about the results from my Suspension Logger mini-project: Hopefully see you on Tuesday. The background for the interest group and info about the meetings can be found here: https://www.caterhamlotus7.club/forum/chitchat/announcing-interest-area-electric-vehicles The minutes of the meetings can be found here: If you’ve not joined the calls before then In brief the agenda will be: Introductions by new attendees What’s new in the EV world Thoughts on Caterham’s plans for EV Seven Conversions AOB Participation in the meetings is, of course, optional. John

Hi all, a quick note to publish the initial results of my Suspension Logger Project. Here's the image you want to see, but there's more information on the project below: The plot above shows time on the horizontal axis and suspension travel on the vertical axis. The suspension travel is measured from the TOF sensor, so increasing numbers on the plot mean the suspension ears are moving downwards and decreasing numbers mean it's moving up. The plot above is of a short part of a trip out in my 420R. The whole trip can be seen below... you can clearly see me getting into the car (twice) at the start, and then getting out at the end. The first plot is towards the end of the one below... There's clearly a lot of noise in the plots, but I got what I wanted out of it, and that's the suspension compresses about 40mm and extends by about 20mm. I'm probably not a lot better off than the maximum allowable travel for the suspension which is +/-50mm, but it was worth this mini-project just to tell me that. Background The idea behind the project was to try and get a ball-park limit on how far the suspension travels on a Seven. I need to know this so I can reliably set limits on the rise/drop angle of two new drive shafts I think I'll be needing in my project. If the real-world rise/drop is too much then the drive-shafts will pop out of the tripod end assemblies.. and that wouldn't be a pretty result! The project electronics consists of a few Adafruit Feather prototype boards and about 400 lines of Arduino code: RP2040 CanBus CPU board (didn't need to be the CanBus version, but that's what I had to hand) VL53L0X Time-of-flight sensor board 128x64 OLED Feather Wing (Just so I could see what the boards were doing and to give me a few switches to start/stop recording etc) Adalogger Feather Wing (with SD Card to record results) After getting the software and hardware running I also 3D printed a widget to attach the T-o-F sensor to my car. Image below: Here's a link to a short video showing my waving my hand over the Time-of-flight sensor.

Hi All, just a quick post to say I've released two "explainer" videos. I've put both together so I can refer back to them in future "progress" videos and I don't need to keep explaining the same things over and over again. You can also find my blog posts about the videos on my website (linked at the bottom of this post). Those blog posts are more about how I made the videos rather than the content of the videos. Here are my website blog posts: https://purplemeanie.co.uk/index.php/2024/02/25/the-electric-in-electric-vehicles-youtube-ptevis-2-1/ https://purplemeanie.co.uk/index.php/2024/03/03/electric-vehicle-components-youtube-ptevis-2-2/

Here are my notes from the recent Caterham Cars webinar. Richard Nichol was joined by Bob Laishley (CEO) and Simon Lambert (CMO, CTO). They spent about 18 minutes of the 1:15 webinar talking about EVs, Seven EV and Project V. Here are my notes: RN: When will we see an Electric race series? SL: EV’s are not good for circuit racing with. Cadwell can’t even put in a car charger. Most circuits are far-flung and so difficult to get power to. Silverstone looking to put in chargers for visitors only. E-fuels is where we might see some. So there won’t be an EV race series any time soon. Hill climbs are more suited to EVs at the moment. RN: How’s the Electric Seven going? BL: Project very expensive and was never envisaged to be commercially viable. Gov decision to move from 2030 to 2035 has taken pressure off EVs. They’ve not seen any “organic pressure” from the market for an electric Seven. They will continue to look at it and evolve though. Learnt that can make and package an EV below 700kg. Therefore useful learning exercise. BL: The cells that were in that project are the same size as Tesla cells but store 3 times the energy and are 5 times the cost. The material costs alone of building each car were £126k. Who will pay getting on for £200k for an EV Seven. BL: Wanted to prove that you could build a 20:20:20… minute drive:charge car. BL: Battery in a formula E car costs getting on for £100k RN: Is that 125k to build and 200k to sell normal margins? BL: Depends on volumes. Just about to re-launch a car in Europe. Will probably only sell 150 cars but homologation costs were about £300k. BL: Prices he’s seen for R100 compliant battery pack testing are around £1m. Therefore the numbers don’t add up if only selling 10% of 750 yearly cars as EV. BL: Holy Grail is to get battery pack costs down to £100/kWh. Need Chinese levels of volume to get to that cost. CC will be more at £500-£600/kWh. RN: Makes the 620 look good value RN: What’s the latest on Project V BL: Everywhere it appears there is great reception. Demand is not from existing Seven owners. Less than 20% of that demand is from Seven owners. BL: Now looking at packaging and choosing suppliers BL: Hope to have a prototype car next year RN: When hand over first keys BL: Early 2027 RN: UK launch or multi-country BL: Like to think UK. But will depend on demand. Will depend on whether that’s a left or right hand drive model. Japan could tip that to RHD. BL: Project is going slower than he’d have hoped. But currently in fund raising phase. BL: Need to absorb north of £100m RN: Will there be a race series for Project V? SL: There’s no class for it at the moment. Would like to see a class but by the time we get there a class will probably have a [lower] weight limit that Project V will be a long way under. RN: It’s an expanding market, will it stack up against competitors and be competitive. BL: Other competitors coming into the market will make the market bigger BL: Other companies have much bigger overheads and so CC can do it BL: Alpine, need to sell 10k a year, Porsche sell 40k Taycans to make that viable. CC only need 2k a year to be viable BL: Don’t think Porsche really a competitor. You have to pay more for a light weight version, CC offering will be light weight to begin with RN: Will Project V open up US market BL: US already open to CC. Sell lots of cars to US already. No plan to launch in US until a couple of years into life cycle BL: Healthy proportion of interest is coming from US though BL: Homologation side of business is a big part of what the company does BL: May have to crash 9-10 cars to get homologated in US. Each car (at that stage of production) would cost $600k to $1m each. Better to do those tests later when can use production cars.

Hi Jonathan, yes, I’d thought about that, and others have suggested things like belts etc. However, an epicyclic gearbox is the perfect solution. They’re small, light, can run in both directions and can deal with the power. The downside is that their complexity increases cost… and I’ll need a custom box designed. But I’ve got a couple of companies giving me what look like reasonable quotes for a design and supply. So, all in all it’s my currently preferred option.

Hi all, unfortunately I can't make this month's SIG meeting next Tuesday. So in lieu of that meeting, here's an update on the project with a few images. I'm also in the process of writing a piece for March's Lowflying that I should hopefully get written before the deadline later this month. As those of you that attended last month's meeting will remember, I've now started to make significant progress with my project. I've been sidelined a little by trying to get two "explainer" videos published to YouTube, but they're very close to being finished now and should go live in the next couple of weeks. The first gives an "explainer" on what forms of electricity are used in an EV (DC and AC) while the second goes into what components I'll be needing in my project. They're meant to be resources that novices can look at to understand what's in an EV, and that I can keep referring back to. Hopefully they'll be useful to anyone wanting to know a bit more of the behind the scenes. Link to a short YouTube video showing how a motor works... this is part of the second video. As for project updates... The big change is that I've decided to explore more fully the idea of a twin rear motor configuration for the car. Each will be a smaller motor of around 120kW, mated to a small 6:1 epicyclic gearbox to reduce the ~12,000rpm of the motors down to ~2,000rpm needed at the wheels. This has the advantage of removing prop-shaft and differential while also improving packaging - meaning I can have more space for batteries up front. See image below... The second big change is that I'm planning to use a high-power DC-to-DC converter that will sit between the battery pack and the twin inverters. This means I can de-couple the voltage of the pack from the voltage required for the motor. One of the critical conundrums of an EV project is to be able to get enough voltage supplied to the motor without significantly increasing the size of the battery pack to accommodate that voltage. A high-power DC-to-DC converter will allow a low pack voltage of say 250V but still drive the motor at 400V. This gives me much more flexibility on the battery options up front. See image below... Finally in big ticket items, I've finalised on how I'll do all the electronics control of the car now. I'm going fully CANbus for the control interfaces and removing the standard gauges to be replaced by an electronic dash. I appreciate that some may baulk at the idea of an electronic dash, but for my "prototype" car I need a much higher density of debug information on a screen. And this should allow me to do that. Another benefit of going completely CAN, is that I can use a Power Delivery Module. This will replace my current fuse box (that would have needed rewiring anyway) and replaces it with 32 programmable "soft" fuses. I expected to have been "blowing" a lot of fuses if they are standard fuses, so having a soft-resettable fusing system will be a big bonus. The PDM can also do a lot of logic functions for me and seems to be a big win-win for the design of the car. It also means there's a lot less wiring to do. Image of AIM dash and switches below... This last CANbus decision has also meant I can replace more of the wiring in the car. This isn't perhaps ideal, I'd have rather keep the current loom as "stock" as possible, but the reality is that an awful lot of it will change anyway and I might as well go all on with it. A consequence of this is that I'll be replacing the wiring to the lights at each corner with a CANbus driven lighting system (of my own design). Prototype board shown below... And finally, finally, I've been diverted a little by a project to determine actual rear suspension travel. I need to know how much suspension travel I'll need so I can get a good handle on the rise/drop angles of the rear suspension - I'll need new half-shafts with the twin motor arrangement. So... me being the type to dive in with a way over engineered solution, I've created a way of "instrumenting" suspension travel using a RP2040 processor and some data-logging prototype boards. See image below and link to YouTube short. The processor samples a distance measurement 30 times a second and records it to an SD-card. The distance is taken using a laser based Time-of-Flight sensor which I attach to the frame of my 420R above the De-dion "ears". As the ears move up and down I record their travel. More info on my results in further reports. Here's an image of the "Suspension Logger", link to video below it... As well as the electronics to capture suspension position, I've also modelled, and printed, a "widget" to attach the T-of-F sensor to the frame of my 420. The processor and data logger sit in the boot of the car (in the dry) and the sensor clips onto the frame in the wheel arch. This arrangement isn't meant to be permanent. And in fact even "temporary" is stretching its use. It will be attached for a few minutes to gather suspension travel information - if I wanted it attached for any longer, and for all weather, then I'd have done something more robust. But this should get me to the data I need. Link to suspension logger video: That's all for now. If you have any questions then please shoot them my way. John

As part of a bigger project I've put together an animation of a simplified Permanent Magnet Synchronous Motor. If you're interested you can find more about it and a link to the video here: https://purplemeanie.co.uk/index.php/2024/01/12/pmsm-motor-internals-video/ If you have any questions or if I've got something wrong then please let me know. John

We aim to Educate! 🙂

For those of you that are interested, Caterham has sent out an email with a link to their latest Project V video. The video is unlisted at the moment, so you can only find it using the link below: John