How to Power Domestic Appliances with your Ebike Hub Motor
Forget “clean coal” it’s a myth, North Sea gas is cleaner than coal but it is still a greenhouse gas emitting fossil fuel, nuclear works but has serous safety issues, solar is great if you have a roof and sunshine, tidal might be OK if you can dam up an estuary, wind is the answer when it is windy.
But what are you supposed to do when you’re out on your ebike and you;
- fancy watching a film on a large screen LED TV that you happen to have brought with you on a bike ride?
- want to power a local band giving an out door performance?
The ChiCycle team imagine a green, pedal powered future so we looked into these ideas as fun ways to illustrate how we use electrical energy in every day life.
Feasibility: it is obviously possible on a small scale:
Science Fiction: These ideas feature in the Black Mirror episode Fifteen-Million-Merits
What follows is an indication only of what ChiCycle has tried and tested. We give no guarantee these ideas are safe for individuals using the equipment nor safe for the equipment being powered. If you choose to replicate any of the setups that ChiCycle has employed, be certain to consider the mechanical risks and risks from high voltage electricity if stepping up the output to power mains appliances.
What Hub Do I Need?
ChiCycle have been experimenting with a rear EBike hub with built in dérailleur gear sprockets. Some EBike hubs won’t easily work as generators as they have freewheels to stop the motor turning unless it is powering the bike. However most other EBike hubs without motor freewheels will make very efficient generators as well as drive motors. You will probably want to find a way to hold the rear wheel off the ground so the E-motor can generate electricity without the bike having to move foward. We have been testing a wheel very similar to the one shown below.
An alternative idea stolen from Barreg Cycles, Fishbourne, is to drill out a single rear sprocket and bolt it onto a front motor hub where the brake disk should normally go. A front hub with brake disk is shown below.
ChiCycle assume the hub is going to work most efficiently as a generator in top gear. However this is just an educated guess.
Most hubs have fine wires for their hall sensors. These are of no significance if the hub is to be used as a crude simple generator.
There are usually three thick wires that connect directly to the three phase motor windings.
At a sustainable but energetic peddling rate in top gear we measure approximately 18 volts AC at 100 Hz with no load.
Spinning the peddles a little faster gives 24 Volts between each phase. Three 24 volt 21 Watt indicator bulbs can be connected between each phase and fully illuminated by pedalling quite quickly.
Powering TVs, computers and other consumer electronics.
Most TV’s, computers, smart phone chargers and even Christmas tree lights operate using internal ultrasonic frequency switch mode transformers. Most UK and European consumer equipment appears to have an extremely wide range of input voltages over which the devices will power up and operate without issue. Most specifications cover a range of 100V to 240V mains AC in the equipment specifications but since these devices internally rectify the incoming AC supply the AC frequency is not critical. In fact most devices seem happy to operate on a DC supply! Ideal rectification of 240 V mains would give 240 V (ac) × √2 = 339 (dc). Assuming the device internal power supply is designed to cope with 20% variation in the mains supply, its storage capacitor and chopper circuit should be able to cope with up to 240 V (ac) × √2 × 1.2 = 407 V (dc). It is likely most UK/EU devices will tolerate higher DC input voltages but finding the upper limit will probably damage the internal power supply so this is not an advised activity. Most consumer equipment we have tested begins working reliably with approximately 100 V dc input. Aiming for a supply voltage under load (at a sustainable pedalling rate) of between 150 and 170 Volts seems a safe option as it is almost impossible to achieve an output of 350 Volts by pedalling too fast. This makes supplying too high a voltage to consumer electronics unlikely. To achieve this we used a circuit similar to the one shown below.