The Improvised Electronic Device was born out of a desire to be electrically self-sustaining in the remote places I plan to go. It’s not that I’m trying to save the planet, I just don’t want my iPod to go flat. While it’s not uncommon for bicycle tourists to have a few gadgets these days, I’ll be travelling with the following electricity-hungry devices:
- Notebook computer
- Digital Camera
- Garmin GPS
- iPod touch
- Mini USB powered speakers
- Zoom H2 field recorder
- Front and rear bicycle lights
- SPOT satellite GPS messenger
My plan was to have a battery pack that could be charged with a standard AC/DC adapter whenever mains power is available. The battery pack could then be used to run or charge any device that needed power, and be gradually topped up by a Schmidt SON dynamo hub on the front wheel of the bicycle. Sadly after much searching I, like others, have come to the conclusion that such a device doesn’t exist.
Charging a battery from a hub dynamo is no simple task. Getting the (fairly small amount of) AC power from the dynamo hub to a battery efficiently is one problem. Being able to also charge the battery using a DC adapter and preventing the battery from exploding due to overcharging is another. Enter the Tunecharger – a circuit made in France which is designed to do… well, exactly that.
The Tunecharger uses MPPT – Maximum Power Point Tracking to feed power to the battery while constantly monitoring the voltage. An End-Of-Charge voltage can be set to prevent overcharging the battery. Thanks to Alex Lockhart and Garote and Chris Devenish (whose blog appears to have disappeared now) – the descriptions of their devices led me on the path to building my own.
The IED contains:
- Tenergy 18650 66mAh battery pack (11.1V nominal)
- Tunecharger circuit
- Texas Instruments PTH08000W circuit
- Texas Instruments PTN78000W circuit
- Random voltage regulator circuit from ebay
- 12V car socket
- Lenovo socket for DC adapter
- 2.1mm DC plugs for 9.3V and 9.0V
- Four USB ports
- LED battery voltage display
- Various status lights
- Lots of switches/button
- The general appearance of having been built by a mad scientist
It remains to be seen whether the device will hold up to the harsh conditions of touring but so far it seems to work.
Hi,
Amazing!
Question: You know, car battery is charged using its alternator when a car is driven. Battery normally does not need external charger as long as it is “alive”; alternator keeps the battery “alive”.
My question is: Can your circuit/design be used in the same way for electric bicycle? If yes, how do you connect it to bicycle? How much it costs?
Please reply. I am very much interested.
Regards
Roy
The bicycle alternator works by stealing a (very small) amount of energy from the rotation of the front wheel and converting that to electricity. The maximum power drawn is approximately 8W at high speed (40-50km/hour) – and there are losses involved in converting the AC power of the hub dynamo in to DC power to charge the battery.
The short the answer is “not really” – any power produced will be less than the power required to move the bicycle – see the Laws Of Thermodynamics.
I would suggest you investigate developments in bicycle regenerative braking which might be more in line with what you want to achieve. Have fun!