Drive it forever
Q. Have you heard about the "pee battery" that Japan invented? I figure that if auto makers did some serious tinkering with the pee-circulating fluid battery they would have another alternate fuel more abundant than gasoline, coal, methane, and natural gas, with the possible exception of wind, solar, and water resources.
The battery works like this: A drop of urine is added to the copper chloride paper sandwiched between strips of magnesium and copper, a chemical reaction takes place and that produces electricity. Biochip system engineering could make the battery commercially available.
Just imagine how such battery power could be used to change all sewage plant power requirements to this source. Even garbage trucks could be run on electricity using this battery, saving cities millions of dollars in fuel costs to operate daily tasks. If shipping made use of this power generation method, oil tanker ships would soon become electric models for transporting fossil fuels.
Neither automakers nor energy awareness groups have posted much about the challenge of meeting our worldwide energy needs, and much work still needs to be considered. Perhaps artificial urine could be made for use on the moon, if development of the moon ever became an incentive. That way, all other sources of fuel on the moon could be saved, rather than used and channeled to the earth. The same holds true with other planets that have more fuel resources than the moon. Don't worry who it's from, urine passes dead cancer cells all the time, they are not harmful.
A. This battery, which is activated by soaking it in urine (or blood, or vinegar, or salt water -- almost anything except distilled water) will never be a viable option for powering anything except a very low-powered device. It is a primary battery, and that means it is not rechargeable. All of the energy in it is available once, like an old-fashioned carbon-zinc D-cell flashlight battery. Batteries used in cars need to be recharged.
It's an interesting concept, but not exactly new technology. Volta used copper-zinc batteries soaked in brine to make dissected frogs jump hundreds of years ago.
Q. I own a 2003 Mercedes E-Class. Is it still necessary to verify the plug gap or even to correct the gap on today's cars with on-board computers? If the plug is beyond the gap specifications, won't the on-board computer compensate/correct for that without skipping a beat? Isn't that what the computer does anyway, as the plugs wear out?
A. The computer really doesn't correct for a changing or incorrect spark plug gap. The plug will fire at whatever voltage is necessary to bridge the gap across its electrode, no more. As the plugs age and the gap widens, the voltage requirements will go up until the coil can't generate enough voltage. Then you've got a misfire.
Most late-model cars use precious-metal plugs that rarely need changing. But I still pull the plugs out every couple of years to check them, and to make sure they haven't seized in the plug holes.
Q. I am installing a radio intended for a car in my boat. On the instructions it shows one red wire (hot) going to the positive side of the battery. How do I complete the circuit without a ground wire?
A. You're right: A radio, or any other current-consuming device, needs a return path to the electrical system to complete the circuit. Car radios are normally grounded where they are bolted to the frame of the dashboard. Additionally, there might be a ground path to the sheet metal along the outer shielding braid of the coaxial cable antenna lead. I do not recommend relying on the co-ax to ground the radio, though.
In answer to your question: There is no way to ground the radio without a ground wire. So, use one. Pick a screw somewhere on the radio chassis that is out of the way, and put a wire with a circular crimp connector under it. Ground the other end of the wire to the battery's negative terminal.
Mike Allen is a senior editor for Popular Mechanics magazine. Questions should be sent via e-mail to driveit@nytimes.com. 
