I briefly mentioned this bike before, when I talked about how I got into bike repair. The bike was “analog” back then, but my wife has meanwhile developed some problems with the tendons on one of her feet, which have impeded her ability to climb hills on the bike. So I’ve built her an e-bike!
Whenever the decision to get an e-bike comes up, one of the first questions to answer is do I buy a dedicated e-bike, or do I convert my existing bike? We chose to go with the second option, for a couple of reasons1:
The bike already fits my wife perfectly. Buying another bike would mean going through the entire process to tweak the fit all over again.
I don’t like being vendor locked. Dedicated e-bikes are often compatible only with parts made by the same manufacturer, especially when it comes to things that fit inside the frame, like batteries or motors.
Just like I never trust second-hand carbon components, I don’t trust second-hand batteries, so we’d have to go with either a brand new bike, or a second-hand bike and a brand new battery. Both options would come out significantly more expensive than the current build.
Not only did we not have to pay someone for the conversion, it was also free entertainment for me!
This has been a tremendously fun project. I had no idea these things are such a blast to ride. I am seriously considering converting my own bike too. It might make me even lazier than I already am, but boy, it’s just so much fun!
The whole experience has also been a great learning opportunity. Some of the stuff I found out about during the initial planning phase, and some came up during the actual build, like it often does. I’d like to share some of my main takeaways with you:
Buy a safe battery pack
Lithium battery packs are built out of individual batteries, called “cells”. The most common cell format is the 18650 (image source), so named because of its cylindrical form and dimensions. The quality of these cells varies greatly across manufacturers, not only in terms of capacity and performance, but more importantly, safety. Lithium batteries can be incredibly dangerous2, so it is vital that you buy the best, safest battery you can afford. Don’t buy off Chinese sellers on Amazon, eBay, or AliExpress, and do some solid research on the seller and brand beforehand. When it comes to the cells, look for packs built with Sanyo/Panasonic, Samsung, or LG cells. Extra safety precautions include storing and charging the battery in a special fireproof container3, not charging it unattended or overnight, and having an ABC fire extinguisher nearby (lithium batteries produce a Class B fire).
Buy components rather than a kit
Buying a pre-made kit does have some important advantages, especially for the first-time builder. When you buy a kit, you know that all the components are compatible with each other; that all the electrical currents and connectors match, and that you don’t forget about some part or cable that you need.
On the other hand, now that I’ve built it, I wouldn’t buy a kit on the next one:
The kits are cheap because the kit builders cheap out on everything they can, even in places where it’s a matter of safety. I rebuilt the wheel right away with solid, high quality components4 that I’m not afraid to let my wife ride on. If you’re going to buy a kit, I strongly suggest you get the wheel checked for safety by a professional wheel builder.
The kit components match each other, but they might not match the particularities of your bike. The pedal assist sensor might not fit your bottom bracket/crankset combination, or the battery rail might not fit your frame5, and the mount system on some displays (like the P850C I installed here) make it impossible to also install any KlickFix accessories, like the Ortlieb bag I use on my bike.
Then there’s a matter of preference, too. Throttle levers, for example, come in many shapes and sizes6, or you might prefer installing in-line brake sensors7 rather than changing your existing levers (this is actually not optional with drop-bar levers).
So, while there’s more upfront work necessary with researching all the components, buying a pre-made kit is in the end more fiddly, and there’s a greater chance you might have to buy some parts separately anyway, or end up with some you don’t need at all.
Whichever route you go, make sure the components have Julet electrical connectors. These provide a solid, waterproof connection that is an absolute must on a bike8.
Buy a ton of zip ties
Seriously, I had no idea I’d need so many damned zip ties. I don’t like cables rattling around, especially this close to the turning cranks and wheels, so I must have used about a hundred of the things. Just buy a couple of bags of them in different sizes.
Which is not to say that dedicated e-bikes don’t have plenty of their own advantages. They do, just none that outweigh the benefits we saw in the conversion project. ↩︎
I used a Ryde Andra 30 rim, DT Swiss Alpine III spokes, and Sapim Polyax nipples. The Andra has angled spoke holes, and when paired with the Polyax nipples it allows the wide-flanged hub motor to be comfortably installed in smaller wheels. ↩︎
Though I actually suggest not installing one at all. They’re too easy to accidentally hook into clothes or handbag straps when pushing the bike or lifting it up and down the train, etc. if you’ve forgotten to turn the system off or to set the pedal assist to zero. ↩︎
So that the controller can cut off power to the motor when you apply the brakes. ↩︎
But I wrapped them in electrical tape anyway, for extra water protection. ↩︎