The interesting thing about batteries is that you can make one out of a potato. Or a tomato. Or even a lemon or lime. In fact, any liquid or moist object that has enough ions to be electrically conductive can serve as the electrolyte for a cell (see Wikipedia.com). Basically, you just need to insert two electrodes made of different metals into the moist object and a chemical reaction occurs when the two metals react via the moist cell, aka: potato. Cool, huh? Of course, this type of "battery" is of no real practical use except to maybe power a small clock for a very short amount of time.
A battery is basically stored chemical energy that is converted to usable electricity when the battery terminals are connected via some material that will transfer(conduct) and allow the two metals to chemically react. Like Nickel and Cadmium in a NiCad battery. Basically, the amount of energy you get (volts) is determined by how much "chemical reaction" you will get between the two metals. It is for this reason that Lithium batteries are the "latest and greatest" thing since powdered milk.
Lithium is a highly reactive alkali metal. Lithium will literally react if left out in open, moist air. Combining with the hydrogen in the water molecules in the air it will turn from a whitish metal to a black tarnish before your very eyes. That is why when lithium is stored in it's pure state, in is stored under oil to keep it from reacting. Lithium is also highly flammable, so if it is already burning, throwing water on it will only make it burn more. Lithium metal needs to be doused with special chemicals to put out the flames. Lithium is also the lightest weight metal (number 3 on the Periodic Table of elements). Those two features, light weight and lots of potential energy, make Lithium a great metal to use in a battery.
Lithium's highly reactive feature is also a downside in the battery making industry. Lithium batteries in computers have "ignited" because of their high reactivity. Dell Computers recently had a massive laptop battery recall (this very computer I am typing on was affected). Lithium batteries give off a lot of heat and have been known to self-combust. The recall cost the industry megabucks but Lithium's advantages far outweigh it's disadvantages and Lithium cell technology is advancing at a rapid pace. "In an interview with BusinessWeek on Feb. 16, Chief Executive Katsuaki Watanabe confirmed that Toyota's third-generation hybrid cars, due out in late 2008 or early 2009, will use lithium-ion batteries. Lighter and more powerful than the current nickel metal hydride packs, the new batteries will help make for more fuel-efficient hybrids. ... "We can develop the battery in time," he says. ... "We are now aiming at reducing, by half, both size and cost of the third-generation hybrid system," says Watanabe."
For most people using batteries, the life of the battery is the most important aspect. How long will it last before I have to recharge/replace it? Basically, disposable batteries, lose from 10-20 percent of their original charge every year, more if stored at extremely high temperatures (battery life can be extended by storing them in a cool place). So the batteries that you buy at the Dollar Store will not necessarily last that long; always check the manufacturers date on the batteries that you are looking to purchase.
Rechargeable batteries self-discharge more rapidly than disposable batteries - up to three percent per day. This rate can decrease in extreme temperatures so keep this in mind if you store your rechargeable, battery-operated power tools/flashlights in your garage. Rechargeable batteries also degrade through use. Low capacity Nickel Metal Hydride(NiMH) and Nickel Cadmium(NiCad) rechargeable batteries for example can be charged for approximately 1000 cycles before pooping out on you. Typically a longer, slower charge (overnight) will result in a longer battery lifespan.
There is also what's called the "memory effect" with regards to batteries. Memory effect happens in NiCad and NiMH batteries when crystals build up on the electrodes and decrease the active surface area that gets charged (wikipedia.com) . This happens when batteries do not get fully discharged before they are recharged. NiCad batteries should always be fully discharged before they are recharged because they suffer more from "memory effect" than NiMH so. The advantage of using Lithium Ion batteries is that like a young dog, they do not have a "memory effect". Charge them whenever you want and they will always be fully charged, ready to run.
To summarize the three most commonly used Power Tool Batteries in order of performance:
3. NiMH:
-performs the worst in cold temperatures
-has the shortest run time
-highest self-discharge level
-lighter in weight than NiCad
2. NiCad:
-performs in cold temperatures to 20F
-lower self-discharge rate than NiMH
-has a lower self-discharge level than NiMH
-heavier in weight
-suffer the worst from "memory effect" if not fully discharged before charging.
1. Lithium Ion: -lightest in weight
-perform well in temperatures as low as zero degrees Farenheit
-have the highest amount of life cycles
-lowest self-discharge rate
-have a more rapid charge time
-do not suffer from the dreaded "memory effect"
**BUT: permanent damage can occur to LiIon batteries if stored at too-low discharge level, so be careful and keep these charged well. Also, They start degrading as soon as they leave the factory. Be sure to check the manufacturers date on the batteries before you purchase.
::PLEASE RECYCLE YOUR BATTERIES::
"Since their development over 250 years ago, [[batteries]] have remained among the most expensive energy sources, and their manufacturing consumes many valuable resources and often involves hazardous chemicals. For this reason most areas now have battery recycling services available to recover some of the more toxic (and sometimes valuable) materials from used batteries. Batteries may be harmful or fatal if swallowed. It is also important to prevent dangerous elements found in some batteries, such as ead, mercury, cadmium, from entering the environment." - wikipedia.com
