Crazy HAM on a bike!

I'm a HAM radio operator and now that I'm retired I've been able to devote a lot of time to a sport I thoroughly enjoy, that sport being cycling. I commuted to work on a bicycle for many years and enjoyed getting out with other cyclists riding back roads or Rail Trails for upwards of 60 miles or so. About twice a year I would do a Century on an organized and supported ride. A Century in bicycling terms is cycling a route totaling 100 miles. With the time I have available now I can actually get out and bicycle tour. This consists of packing camping equipment on a bicycle specifically designed for riding hundreds of miles loaded with camping equipment that would destroy a "normal" bicycle in short order. Here is a site dedicated to bicycle touring.

http://www.crazyguyonabike.com/

I've done a few tours now and found I really wanted to take a QRP transceiver with me. The only problem was the power required to operate the equipment. Unlike your car or truck with its battery a bicycle does not require a battery. Even in countries like Germany where bicycles are required to have lights for road use no battery is required. A dynamo driven from the tire generates power to run the lights. Here is the dynamo I use.

When I tour I camp as well so there is no place to plug in a battery charger. Staying a single night in a motel would allow me to charge my batteries but the cost of that room could feed me for an entire week on the tour. I don't want to credit card tour as some cycling tourists do. I might as well have the wife following me around in an RV if I did that. That's not "real" self supported bicycle touring. That's where "Crazy HAM on a bike" comes from! Hams think I'm crazy for riding a bike for miles on end and cyclists think I'm crazy to haul a radio and charge the batteries with a dynamo with its additional drag, in the daylight, while cycling!

How a bicycle dynamo works.

A standard bicycle Dynamo will supply 500mA of current when driven at its rated speed or faster. It uses a magnet rotating in a coil of wire so there is no voltage or current regulation. It's a constant current device. You get 500mA of current no matter what you have connected to it. If you connect a light to the dynamo that only draws 250mA the bulb will quickly burn out. If the bulb draws more than 500mA the voltage produced will be lower than 6-volts so the bulb will be dim. The dynamo is designed to produce power for a bulbs requiring exactly 6-volts AC with a current of 500mA or 3-watts.

In the 1950's Germany required all bicycles used on roads to be fitted with lights. They determined 3-watts was acceptable and 6-volts was the common voltage used on vehicles at the time. Other countries adopted the same standards. Here we are 50 years later with the same standards with almost all bicycle dynamo driven lighting systems using the same standard worldwide.

Charging batteries with a bicycle dynamo.

It's easy! Much easier than you would think possible considering the limitations of a bicycle dynamo with its alternating current and unregulated voltage output. All that's required is a simple bridge rectifier consisting of 4 1N5818 diodes. I included a 470mF capacitor in the circuit as well. It's not required as the batteries will smooth the ripple produced by the AC to DC conversion but I wanted to be able to power My LED headlight and taillight on the bicycle if my batteries were damaged or lost and I had to ride after dark or through a tunnel. Not only may I recharge the batteries for the QRP transceiver other devices like a GPS unit or a Cell Phone may be recharged as well. Here is the circuit I currently use.

The battery pack actually consists of 3 parallel-connected packs of 4 series connected Ni-MH batteries wired for a circuit voltage of 4.8 VDC. This voltage meets the standards set for USB ports on computers. When the batteries are removed from the bicycle and the 3 battery packs are connected in series 14.4 volts is available for the QRP transceiver. While I am pedaling along with S1 open and S2 closed the dynamo is recharging the batteries at the maximum suggested rapid rate of 500mA. So what about voltage regulation? The batteries are automatically doing that as well! As the voltage produced by the dynamo approaches the rated voltage for the batteries they start to impose high impedance load on the dynamo consequently preventing excess voltage. I've recharged as few as 2 Ni-MH batteries with the voltage regulated at 2.9 VDC, perfect for Ni-MH batteries. 9.6-volt R/C battery packs are the highest voltage I've been able to obtain from my 6-volt rated dynamo for recharging purposes. I selected 4.8 volts for several reasons. The QRP transceiver operates just fine at 14.4 volts with the 3 series connected 4.8-volt battery packs as does other radio equipment designed for 13.8-volt automotive systems. 4.8-volts is correct for operating and recharging electronics, which plug into a USB port. This includes Cell Phones and GPS units. My headlight and taillight also operate from the dynamo and batteries. Very little resistance is required to drop 4.8-volts to 3.6-volts for the 350mA Headlight LED and 1.9-volts for the 36mA taillight LED increasing the efficiency of both. There also much brighter than standard filament bulbs and don't burn out so you never need to carry extra bulbs. Here I am with my touring bike.

I did not include information about my QRP equipment or QRP operating as this article is really about charging batteries for the equipment I use. Articles about operating QRP abound here and on other sites.