BACKYARD BLISS | Tips for building your own eco-friendly electric bike

A few years ago we decided to electrify our bikes. Don't get me wrong, we loved the hair-raising joy of blasting down a hill and connecting directly to our pedal-powered freedom machine.

However, that keenness can wear thin riding home in a dark drizzle in the middle of winter facing hill after hill. Enter the electric pushbike.

These have evolved a fair bit over the years, firstly motors have become more efficient/powerful and most importantly battery technology has leaped forward thanks largely to mobile phones.

There are lots of new e-bikes out there ranging in price from $1000 to $5000. Unsurprisingly, at the cheaper end they're pretty poor quality, at the top end, amazing.

We chose to convert Hannah's existing bike instead of buying a new one, as her bike frame was super sturdy and had good components. All up, the quality conversion kit we got cost around $1000.

There's two kinds of drives for electric bikes, hub drives and direct drives. Hub drives sit in the wheel and are a very clever bit of tech. They do however move a considerable chunk of weight to the front or the back and require extra strong forks to handle the force the motor exerts - hence why many e-bikes look a bit overweight.

Direct drives have the advantage of powering through the existing gears of the bike, in effect increasing the power, especially at low speeds. Given the last part of a path to our place is a 30 degree slope, this feature was essential.

A 250 Watt motor is the largest you can use without registering the vehicle. That law is derived from this being the upper amount of energy a pedaling human can supply. As a useful vehicle, say for towing a load, a larger motor would be great. However, given the legalities we opted for a road legal 250W motor.

We chose a Bafang 8 Fun 250W Middle Drive Motor for the conversion. It's elegant design allowed the motor to be installed through the bottom bracket of the bike, delivering weight and energy to the strongest part of the frame.

First off, I stripped the bike, ready for the install. I took the opportunity to strip off many of the old components, gave the bike a clean and a new paint job, thanks to some spray paint I found in our shed.

Before attaching the motor, I had to remove the pedals, crank and bottom bracket. Most folks will need to visit a bike shop or bike kitchen to access the tools to do this - we went along to Hobart Bike Kitchen where they gave me a hand.

Next the motor and sprocket where assembled. The motor was then inserted in the bottom bracket with collar nuts to hold it in place. Then I re-attached the cranks and pedals.

In setting up the handlebars I attached all of the components, including two new brake levers, there was also a controller and the on-off and booster switch.

Next the battery pack was attached, this unit attached to the lugs that hold on the water bottle. The speed sensor and magnet were then attached to the back wheel. And the last bit was to connect all the cables neatly.

Viola, an electric bike! And it's awesome.

This bike is great fun to ride. The weight is down low and it feels very similar to a normal push bike. It also hoons up and down hills. A standard 30 minute ride home (up decent hills) is down to 12 minutes.

The bike has a 12 Ah, 36V battery that can supply a maximum of 432 Wh of energy. At an average speed of 25Km/h using 250W, we can travel for 1.7 hours or around 43km. This equals about 10Wh per km. This 43km is powered by around 30 minutes of our home solar power system, or the equivalent of a 100W light globe for four hours - pretty good value for energy if you ask me.