All the latest 2009 sportbikes are truly advanced pieces of machinery, but some of the technology they use is actually pretty old-and none more so than the battery. In fact, the rechargeable battery technology used in almost all bikes (and cars) is the oldest there is: lead acid batteries were invented 150 years ago in 1859 by French physicist Gaston Plante. He discovered that sheets of lead dipped in a sulfuric acid solution generated electricity, and could be recharged over and over again.
When there have been such huge advances in electronics why are we still using chunks of heavy, deadly lead dipped in poisonous, corrosive sulfuric acid to power our bikes? The truth is, despite its low-tech appearance, the good old lead/acid battery has a few characteristics that make it ideal for bikes and cars; characteristics that more modern battery technologies -like your laptop's lithium-ion battery or cell phone's polymer battery-just can't match.
The main advantage is that lead batteries can pump out a lot of electrical charge in a short period of time- just what you need for starting an engine. The biggest drain placed on your battery occurs when you thumb the starter button, and no other battery technology can physically pass the amount of electricity needed to crank over a high compression engine from a cold temperature and spin it up fast enough and long enough to start.
And it's not just the starter motor-modern bikes have more electrical demands than ever before. Fuel injection systems have powerful ECU 'brains,' the fuel injectors draw a lot of power, and the injection system also needs a large pump to maintain the pressure needed for the injectors. Other systems like anti-lock brakes drain even more power, and when you add in gizmos like GPS, an iPod or LED light kit it's a wonder your bike's battery copes at all.
Old Gaston's basic design hasn't changed too much in principle: the battery in your bike uses lead plates immersed in diluted sulfuric acid. The chemical process that takes place between the lead and the acid generates an electrical charge - around 2.1 volts per cell. Arrange six of these cells side by side, and you have a 12-volt battery.
When discharged, the lead in the plates turns into lead sulfate and the sulfuric acid becomes more diluted. Charging the battery reverses this process, turning the lead sulfate back into lead, and increasing the strength of the acid again. The acid contains water, which can evaporate over time, so the level of fluid inside the battery needs to be checked. If the level drops, it needs to be topped up with distilled water.
The chemical process is the same as in Gaston's day, but there have been a host of refinements aimed at improving the efficiency, reliability and longevity of the battery. Adding calcium or antimony makes the lead plates physically stronger, making the battery more rugged, and allowing it to be made thinner. Making the plates thinner and incorporating a grid shape increases the surface area inside the cells. More surface area for the chemical process to act on means more electricity can be produced.
here's what a traditional...
here's what a traditional acid-flooded battery looks like after it's been neglected. clearly it has suffered major corrosion and couldn't jump-start a mouse's tricycle.
To keep the plates apart, some sort of separating material is needed. This can be any non-conducting, porous material, but it has to resist attack by the acid and needs some other physical characteristics. Most current designs use fiberglass, but rubber, PVC and even wood have all been used in the past.
Batteries also need to breathe. They release hydrogen gas when charging, so they need a vent hose. More modern designs have sealed casings with special vent valves. These prevent acid leaking out if the battery is overturned, yet allow the gasses to escape. These sealed batteries are also called maintenance-free batteries, and unlike old-style batteries they never need topping up with water.