by Ken Torino
This is the fifth in a series of article about human energy.
The original Power Box was designed with the idea of providing a low cost, lightweight pedal generator so that it would be within the reach of the largest number of people. To aid in the universal nature of the device we wanted the most universal electrical interface. This is the power outlet found in the home. Because there are many standards around the world we went with a universal socket that would work anywhere in the world. We also went with DC not AC as it is more efficient to convert DC to DC from the voltage put out by the generator and that is in house hold power outlets. DC was also acceptable to switching chargers the dominant type used in the world. These usually say on them that they work from 100-240 Volts and 50-60 HZ. This allows the makers to make one type and use it worldwide. It also meets the European requirement that it uses no power if left plugged in as most chargers are. These design decisions turned out to be correct and many customers appreciate the fact that they can plug in a wide range of chargers that work with most portable electronics. The power outlet standard is not likely to change so this will be true in the future as well. The main request was from those charging 12 Volt batteries to build a larger model so it can charge 12 Volt batteries faster.
In our next model the Power Box 50 we optimized for this application. It has a much larger generator and puts out 14 volts so that it can directly charge 12-volt batteries at 3 amps compared to .8 with the original power box. The output is an automotive socket, which is also a widely accepted interface. With 14-volt output, the wide range of products that plug into an automotive socket can be used. As an example, we carry a 12-volt to dual 3.1-amp USB product. This allows two cell phones or tablets or any product capable of being charged from a USB to be charged using fast mode at the same time. An inverter such as our 150- or 300-Watt models can also be plugged in directly. Last, the 12 Volt to alligator clip included with the unit can be used to directly charge 12 Volt batteries. With a charged 12 Volt battery and inverter connected to the battery a wide range of applications opens up. Let look at a few common ones, charging a laptop or powering a motor such as a furnace, well water or sump pump.
Laptops that are not chargeable from a USB typically use a 45-90 watt wall charger. The 50-watt unit will charge a battery at up to 14 volts and 3 amps. So the Power Box 50 can almost charge a laptop at 1 to 1, one minute pedaling to one minute charging on the low end and 2 to 1 or two minutes pedaling to one minute charging on the high end. The 12-volt battery does not need to be large, less than 10 AH or amp hours.
Another application is a dead starting battery, be it a car, boat, snowmobile or whatever. 5 minutes is enough pedaling to put enough energy in a battery to start an average size engine. A 4-6 cylinder average car engine will use .21 amp hours to start, so 4.2 minutes is enough to put .21 amp hours into a battery with the Power Box 50. Link below gives you a way to get a more accurate number for your engine.
Calculating Engine Starter’s Energy Use
Another powerful application is running a motor such as a furnace when no electricity is available. Most of these motors are ¼ HP to 1/3 HP. ¼ HP is 750 watts and a third is 250 watts. A furnace can be run in a 6 to one ratio. So you can run your furnace, and have heat for 10 minutes for every 60 minutes of pedaling. This is enough to keep you going in emergency conditions or say in winter when an ice storm knocks out power for days. Your primary source of heat is in the gas, propane or whatever the source but it will not work without the electricity on to run the furnace fan. This can be enough to keep the house from getting too cold. Similarly if you have well water you can pump a lot of water in ten minutes. Normally I do not consider applications with compressors good applications for human power as they use so much power. But a typical refrigerator uses 300 Watts average and 10 minutes an hour could be enough to keep critical medicine refrigerated or a freezer full of meat from spoiling. In the case of flooding a sump pump can be the difference between some damage or extensive damage and this will allow 10 minutes per hour and a lot of water can be pump in ten minutes with a 1/3 HP motor. Trolling motor you can limp back in by recharging the battery with a pedal generator.
In the next issue, I will go into more detail on how to connect an inverter and battery to run these applications and how to wire home wiring to make it easy to run off of battery.