72v ebike shopping list

OK, so I have stuff coming in thick and fast – but it seems as soon as I think of something, then there’s something else I need which is crucial to this 72v build… SO, as part aide-memoire, part a starting point for anybody else looking to put together a 72v ebike from scratch here’s a list of what you’re gonna need.

  • The Bike – I’m using an aluminium framed 700c wheeled hybrid which I had in my shed – you might want to consider a 26inch wheel mountain bike as the torque required from the motor is less. Also, full suspension will help – you’re effectively building a moped – mopeds have suspension for a reason!
  • Upgraded brakes – You’re gonna have to stop from 30 mph, so discs or very good v brakes are required [ done] {£50 off ebay}
  • e-brakes – a set of switches or pre-built e-brakes to ensure you don’t haul on the anchors while you’ve still got your motor whirring (these cut power to the motor to stop shredding gears) – [done] {$40} off endless sphere
  • Motor – I’m using a Bafang 350w 28″ brushless, front wheel hub motor which I am assured will take the strain (apart perhaps from the gears -see below) [done] {£75 imported from China}
  • Replacement motor gears – Entirely dependent upon the motor you’re using, but in my case I’m using a 350w Bafang unit with nylon gears in 28″ wheels – that’s a lot of torque (remember with 72v you’ll be putting 2000w throught that 350w motor) to be putting through nylon gears and they have been known to strip threads very easily – the word on the street seems to be – talk to your nearest gear cutter – you can’t buy them on ebay. [to do] {£??}
  • wire – you’re wiring two batteries together which will be putting out lots of amps – 35A wire (10AWG) is a minimum [done] {£17 maplin}
  • battery power – 72V worth (obviously) [done] {£350 off ebay – and I bought cheap (2x 36v 10ah batteries from mp3hk) which lead to more expense}
  • controller – In my case a multi-voltage infineon controller from ecrazyman via knuckles. [on order] {£70}
  • Cycle Analyst – the computer which makes sense of all the stuff you’re doing (not essential, but highly recommended) [on order] {$150 inc postage from Canada}
  • Connectors – high quality connectors and switchgear rated for 35a or higher – Anderson connectors are recommended [done] {total ~ £50}
  • Fuses – you’ll need 35A fuses between your batteries and your controller [done] {inline blade automotive fuseholders/fuses  -£6 halfords}
  • Some kind of box to put it all in – I’ve tried various plastic boxes but it’s hard to find one which fits everything – I ended up buying a sheet of steel (£30) and a pop-rivet gun (£14)
  • You’re going to need tools – standard bike tools obviously, but a good quality soldering iron and volt meter are also essential [don] {£30 – Maplin}

You do the Maths – this isn’t a cheap exercise – I could have bought a cheap motorcycle for significantly less than this project has cost – I reckon it’s getting on for £800 in total (and that doesn’t include the donor bike) – I’ve spent it over 4 months, and justified it by quitting smoking and what it will save me in petrol – but I’ve only had 2 weeks worth of cycling yet (on a 36v bike at 18mph – which proved the concept fabulously – this bike cost roughly half of the total thus far and is an excellent place to start – count out the second battery, the cycle analyst and half the price of the controller).

The biggest frustration in building an ebike is the waiting – for parts to arrive from all over the globe so a well organised bill of materials and schedule will no doubt cut down the build time I’ve had so far – but then this is a hobby, not a job!

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