The BionX option for electric bicycle conversion

For those of you interested in electric motors for bicycles the BionX system is an option. I’ve been meaning to write something about them for quite some time as they have been around for a few years and have a number of models to choose from.

Instead of the more common front wheel motor seen on the likes of Schwinn’s electric bikes (previous post) and others the BionX motor replaces the rear hub and uses a battery that fixes to your water bottle mounts or a custom carrier like the one in the picture below. From my perspective this systems has advantages and disadvantages.

BionX system on a recumbent

The advantage being that you don’t have to worry about running more wiring down to the front wheel, no rack is required to support the battery and it all fits together in a nice tidy system that is even compatible with disk brakes.

The system is controlled by the rider and uses a strain gauge to enable the motor to provide a number of preset levels of assistance on top of the effort being expended by the rider. Depending on which model you buy the assistance can be anywhere from 25 to 300 percent.

The disadvantages are that the BionX system cannot use your existing rear cassette (gears).

The strain gauge measuring the rider’s effort is located on the shaft, exactly where you insert the cassette. This is why the BionX motor can only be installed with a threaded free wheel. And free wheels available on the market count a maximum of 8 gears. BionX has 8-speed free wheels 13-28, 13-32 & 9-speed 13-32 in stock for BionX dealers to order.

For those with nine or even ten speed cassettes this may require some minor modifications and tuning of your rear dérailleur. It is also fairly heavy but considering the assistance provided and the fact that you can get ranges up to 100km on the low settings the weight really won’t be that much of an issue.

The good news is that the BionX system is available in Australia through Greenspeed in Victoria.


3 Responses

  1. I need a wiring diaram for a bionx kit. The reason is that I have recently acquired a used system and it came without a charge system. I have the need to figure out how I am going to charge the batteries when it isn’t in motion. I tried to rig a charger system using an old 34 dc volt 2 wire adapter, but somehow I think that I may have over loaded or shorted out something that now prevents me from getting any sort of charde happening. I am at LOSS, and need assistance with my problem. Is there any one out there that can help me?

    • if you havent fried ithe electronics i could send you a charger what model is it

  2. contact me at

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