Making open source hardware for a depreciated electric bike

West coast stateside company makes a cute aesthetic electric bike, sells a few thousand bikes and then goes out of business. It is hard to ship hardware and bikes are hard to make at that quantity. What are the buyers to do to repair things when parts go bad?

It's frustrating that somewhere, there's documentation detailing the coms protocol for the battery, the torque thresholds for the motor controller, and everything in between. Unfortunately that is nowhere to be found. These bicycles were purchased for 3,500 USD, and one winter in a garage results in them being bricks. Lets undo that with opensource hardware and documentation.

A quick overview of the Faraday Cortland

Here's a quick advertisement from [Link] listing the Faraday Cortland's pricing and some specifications. $3,499 USD is steep. One of the awesome parts of this advert is, it's the exact one I picked up second hand. Overall, it is a beautiful machine, so lets see how much effort is required to wake it back up, and maybe develop open source hardware for keeping these running.

Formulating A Plan

Collecting all publicly available documentation

With the Faraday website down and some things still working from archive.org We have a few documents to reference from. Note that archive.org seems to have struggled indexing faraday's site, a lot of things are broken, and there's a lot of digging as a result, so i'm going to dump everything here in an organized fashion.

Quick start Guide

[Link] This guide is a basic 2 page how to use the bike, not super useful but it does get us this nice graphic:

Guide to replacing mode selector

[Link] This 7 page writeup is specific to the Porteur, but probably also applies to the Cortland model. While this only details removing the module and replacing it, but we do get a note that the throttle and display are all on one cable. normally for these kind of things the "throttle" is hall effect and the display is voltage driven. If I were designing this from scratch, given that we know there are ~12 bars on the state of charge gauge, you could get away with a 4 conductor cable: +5V, Gnd, throttle switch state (analog output) and display input (analog or PWM). Displaying 12 states from analog is fine, but given that the controller is likely some modified bafang-thing, they may have opted for a simple low Hz PWM. Something low enough to not interfere with the three-state assist selector switch.

Dealer Handbook

[Link] Now we're getting somewhere, this is a 45 page document intended for dealers who sell, repair or replace parts on these bikes. There is a lot of marketing-speak, but we do get some good diagrams and a lot of step by step photos.

Seat Technical Bulletin

[Link] This doesn't really get us any useful information aside from a note that the bottom brackets are not swappable between different years of bikes, which kind of makes sense as the change from a derailleur to a internal hub gearbox.

Faraday Company Pitch / Tech Talk [2012]

[Link] This is mostly a talk about kickstarter, and a lot of Faraday company lore.

The Faraday Bike Patent [2015]

[Link] This is also not super helpful but it is probably the main value for the Faraday company when they were bought out, having a patent to "putting a battery in a tube". We get some hints as to the earlier variant of this bikes construction.

Faraday Software Files

[Link] Things are getting exciting, we've found some software files up from archive.org. We have the following file folders:

BACDoor:

Utility for installing updates to the BAC and advanced troubleshooting. Use with caution.

BAC Firmware:

Literally just a copy of the battery compiled firmware: BAC Application 5792.exh

Battery Utility:

A utility to check pack voltage and cell balance. Works best after selecting BAC Update on the Faraday Utility

Faraday Utility:

The primary utility for debugging and update a Faraday bicycle

Motor Parameters:

NCTE 43V 11 Rev3.xml TDCM 43V 11 Rev3.xml THUN Rev4 36V.xml

RCB Firmware

RearController V2.2.4r.hex

Selector Firmware

Selector-nRF51-Firmware-2.1.2r-application.hex

lets look at the motor parameter xml files

We have three options, and these appear to be specific to the torque sensor used. The parameters in the XML file are unlabeled so it's mostly guessing. There are hints otherwise that the controllers are custom Bafang's, so we can look to see if Bafang has some kind of specification for what parameter is what for their config files. I've seen a Bafang programmer app from Luna Cycle which is probably a good place to start. We can try plugging in an XML file from archive.org and see how it populates. The app is available from here: [Link] and in case it's pulled down it's also served locally from here: [Link]. Curiously the file formats are completely different, so no insights from this tool.

We need to make one of these communication cables, without much in terms of documentation. We know it mounts as a COM port, so it's either RS485 or RS232.

State of Charge Display wakes up

With the battery doing something, lets keep an eye on this custom-ish state of charge display in the handle.

Replacing The Stock Battery

I was able to scrounge up some footage from archive.org including a link to a now unlisted youtube video. This appears to be parts of a service video. We see how the battery itself is installed, and yep it requires taking apart the crank assembly which is a bit of work. I get it though, as ideally you never have to replace the battery itself, it's walled off inside the frame. The two little set-screws holding it in place are an interesting choice, I imagine this is mostly to ensure that the pack itself doesnt vertically slide up and down.

Here's a full copy of the ~5 minute video for future preservation [74 MB]: [Link]

Designing a replacement battery

We know that the in-tube battery is a 12S2P configuration, with a nameplate capacity of 306 wh. This equates to 12.75wh 18650's or 3.5ah cells? . That's surprising, given these were manufactured starting 2016.

Concluding Remarks:

• Schematic reverse engineering is tenuous when there's only one bike to test from

• point 1

• point 2

• point 3