Aphid EV

Two years and a static site generator

2026-05-18T00:00:00+00:00

Two years ago today I published the first post on this blog and laid out a plan: take a 1961 VW Beetle, drop in a Nissan Leaf drivetrain, and document everything along the way.

I had a lot of momentum at the start. Then… I went quiet. Sorry about that.

What happened?

Short version: life happened. This was never going to be steady, consistent work towards a road-legal vehicle — it will likely take many years, maybe even a decade. Things get in the way. The longer the gaps, the more important it is to document what we’re doing so it’s less tedious to pick the project back up.

Once coding agents started getting good, I began building all kinds of tools for myself. One was a Markdown note-taking app to replace Obsidian at work, and that’s where I learned how powerful Markdown parsing can be. From there an idea started forming: replace the Aphid EV Jekyll site with something better suited to my writing — split between a build log and a research wiki, and resilient to the occasional two-year hiatus.

I really liked the workflow of a static site generator building the site straight from a GitHub repo; I just wanted it to work a bit differently from Jekyll. I looked into Hugo, which seemed flexible enough to do what I wanted, but I couldn’t find a theme I liked.

I was fairly certain Claude and I could put together a working SSG over a weekend or two. The real tipping point came when I tried Claude Design — that was definitely the missing piece for putting together a nice-looking theme on top of it.

Here we are. If procrastination has a peak, I’m fairly confident I just found it.

So what is aphid?

Aphid is a small static site generator I wrote specifically for this project. The Beetle is already called Aphid, the project is full of leaf-eating jokes, and at this point it felt rude not to keep the pun going.

The previous site ran on Jekyll, which worked perfectly fine. I just wanted something that:

treated the build log and the reference material as two different things — a chronological blog up front, and a navigable wiki of Parts, components and decisions next to it,
understood [[wiki-links]] natively, so links to the inverter or the EM57 motor get checked at build time instead of rotting silently,
built fast and let me iterate locally without thinking about Ruby. This site builds in less than 10 ms

It now does, and the site you’re reading is the third one published with it, at the new (proper Swedish) domain https://bladlus.se.

Back to the actual project?

The detour is over. The car still needs an EV conversion. The DIY VCM still needs firmware. The battery pack still needs cells. I’ll try to be a bit quicker with the next update — no promises about how much quicker.

The safety concept

2024-05-31T00:00:00+00:00

Before any firmware gets written I want to be clear about how the car is supposed to fail. There are two ways the Aphid can hurt someone:

The motor produces torque it shouldn’t — unintended acceleration or braking.
Something exposes the high voltage rails when they shouldn’t be live.

The convenient thing is that both are addressed by the same safe state: open the battery contactors. No HV at the inverter means no torque, and no HV anywhere means no shock hazard.

Important

No single fault is ever allowed to cause a dangerous situation, and no single fault is ever allowed to go undetected.

Motor torque control

That rule pushes the whole design toward dual-channel everything: two accelerator sensors that have to agree, two pedal-supply lines that have to land in spec, two microcontrollers in the DIY VCM watching each other.

The accelerator and brake inputs are read by both the main MCU and the monitor MCU and cross-checked. The monitor MCU also watches the EV-CAN bus and verifies the torque the main MCU is actually requesting matches what the pedal is doing. If anything disagrees, the monitor MCU drops the high-side feed to the battery contactors and the car coasts to a halt.

The interlock loop

The high-side feed doesn’t just go straight from the monitor MCU to the contactors. It runs through an interlock loop that also passes through the lid switches on the PDM and the Nissan Leaf traction inverter, and through the dashboard e-stop. Open any of them — service the drivetrain, hit the big red button, or have the monitor MCU decide something’s off — and the contactors drop.

That’s it, more or less

This blog post is the short version. The full reference, with the error table and the definitions for “accelerating torque” vs “braking torque”, lives in the Safety architecture wiki page. The matching design constraints on the VCM hardware are in VCM requirements.

Next up: actually starting on the firmware.

The Aphid project

2024-05-18T00:00:00+00:00

The name Aphid comes from the small bug that lives among the leaves of plants. The Swedish name is bladlus, which translates to leaf louse — which sounds like the perfect name for when you combine the drivetrain from a Nissan Leaf with a VW Beetle, or a Bug.

I’ve learned from similar projects in the past that blogging about it is a great way to document the work for myself. As an added bonus, I hope to collect a lot of information around doing an EV conversion for anyone else who’s interested.

The timeline

History

When I was a kid, my dad restored an old VW Beetle that he used to drive to work. I remember riding in the back seat that didn’t have any seatbelts. I remember the smell inside the car on a warm summer day. Most of all I remember the very distinct sound of the air-cooled four cylinder boxer engine.

More or less since I graduated from university 15 years ago, I have been working with electric vehicles in some form. All this time I’ve had an idea that it would be really fun to make an EV conversion of an old VW Beetle. It would be such a mindf**k to glide around in one completely silent.

My younger brother is a much bigger car enthusiast than I am, especially when it comes to old VW cars. A few years ago he managed to buy the exact car we had when I was a child, even though he probably never rode in it. Since then it has been parked in his barn waiting for a purpose.

Today

I recently turned 40, and as a birthday gift my brother bought me a used Nissan EM57 motor with a very specific project in mind…

Future

This will likely take us many years before we have something that can be used to drive around on public streets, if we ever get there. My plan is at least to document this with as much detail as possible on this blog.

The plan

The plan is to restore the car to a nice condition. In addition to that, replace the internal combustion engine in the VW with the electric drive unit from a Nissan Leaf but keep the original gearbox locked in 2nd or 3rd gear. We want to do this in such a way that the car can be registered as a modified vehicle and be road-legal to drive in Sweden.

The donor components — see the Nissan Leaf EM57 motor and the Nissan Leaf traction inverter — come from a Gen 2 Nissan Leaf. The vehicle control side is custom; see VCM requirements for what that module needs to do.