TypewriterFrom The Urbach Letter – April 2008

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Battery Smarts Battery Smarts
When I was a kid (in the 1960's), buying batteries was simple. There weren't many choices. You just went down to the corner store and asked for some double-A's, C-cells, or "flashlight batteries." Size was the only thing that mattered. There was just one battery "technology," and except for radios, motorized toys, and flashlights, few devices even needed batteries. Wow, are things different now! Look at the size of the battery display in the store. There are dozens of different battery sizes in common use, and many new technologies to choose from. It's a jungle out there. That's why I wrote this "field guide" to help you navigate your way through… and make smarter decisions when it comes to powering all the electronic devices that are now an integral part of modern life.

Ben Franklin KiteBenjamin Franklin would be so disappointed in you. 21st century folks take electricity for granted… possibly more so than any other modern technology. We walk into a room, flip the light switch, and go about our lives without a single thought about all the "behind the scenes" tech stuff that makes our lights go on. We never think about the generators, transformers, power lines, breakers, etc., that deliver power to our homes and offices… until… a blackout. Then we think about it. A lot. Same thing with batteries. We take batteries for granted. Until they run down – and leave us stranded, holding expensive non-functioning devices in our hands.

Batteries 101. All batteries operate by turning chemical reactions into electricity. They're like little energy conversion factories. While you don't need to know all the technical details to make better battery choices, a little understanding goes a long way. Everything important is in this short article. After you read it, you'll be able to "talk tech" with the best of them. You can even make your own battery with an ordinary potato and two thin strips of metal (one zinc and one copper). They represent the three main things you need to make any kind of battery: (1) an anode, (2) a cathode, and (3) an electrolyte. WAIT! Don't go away! This will get interesting soon… I promise. I know this kind of anode cathode electrolyte talk is giving you bad flashbacks to high school chemistry class. However, unlike Mister Beaker's chem class, this one has no mid-term exams, and you might learn something you can apply in real life. However… if you're already getting cold sweats and palpitations, just skip to the next section.

Potato BatteryBack to our potato battery. If you poke the zinc strip into one end of the potato, it'll become an anode. Anode just means "negative terminal." Of course, you know that batteries have + (positive) and - (negative) ends. Anodes chuck off electrons and start them flowing on down the line (to power your electronic device). Stick the copper strip in, and it becomes the cathode. Cathode just means "positive terminal." It takes in the electrons as they return from their journey through your electronic device. The potato is mildly acidic and functions as an electrolyte. Like the acid in your car battery, the potato completes the electric circuit and promotes the transfer of electrons.

The potato battery really works, but it's far from state-of-the-art. You can power a small digital clock or other very low-drain device with it, but not much else. Besides, you'd look very silly with a potato strapped to your cell phone. Fortunately, there are better ways to build a battery. By choosing anode and cathode materials with high "electromotive force," stronger electrolytes, and better packaging, manufacturers have packed a lot of power in a small, lightweight package. There's been a ton of trial and error along the way – ever since Count Alessandro Volta invented the first battery over two hundred years ago. Tens of thousands of combinations have been tried, some with disastrous results (mainly explosions). Most people feel we're now close to having developed the ultimate in battery technology – considering all factors: cost, reliability, long life, safety, energy density, etc. The ten different technologies described in the rest of this article pretty much represent the full range (although each entails its own set of tradeoffs). Future breakthroughs will probably come from mini fuel cells or other kinds of energy conversion devices. But anything is possible…

The Taxonomy of Batteries

1. Zinc-Carbon. CoreThese are the "corner store" batteries of my youth. They were all we had back then and represent the bottom of the line today. Zinc-Carbons (ZC's) were the first "dry cells." A wet cell is like your car battery – full of liquid sulfuric acid sloshing around – and therefore not a good choice for your flashlight or PDA. Way back when, people were really excited when dry cells became the first available "household battery." They use zinc anodes and manganese dioxide as the cathode. {Stop freaking out about the chemical names you lightweight!} The electrolyte is sulfuric acid, although it's in a non-liquid state; powdered or gelled. The anode and cathode are formed as concentric cylinders, with an insulating sleeve between them. In a perfect world, the zinc anode will be "digested" evenly from the inside out as the battery is discharged. However, what often happens is the process doesn't happen evenly as it should, and the acid eats right through the zinc casing and insulator, leaking out and (usually) ruining the device it's in. This is a major drag. It's bad enough to lose a flashlight or radio, but with portable electronic gear costing hundreds of dollars, trying to save a couple of bucks buying cheap zinc-carbon batteries seems downright foolish. There's another reason why ZC's are on the endangered list: they don't have much staying power, and when they begin to run down, their power curve is ugly. Most single cells have the same output voltage when new: either 1.5 volts for "primary batteries" (ones that can't be recharged) or 1.25 volts for "secondaries" (rechargeables). Most batteries will maintain that voltage until the bitter end. Not ZC's. As they discharge, the voltage falls lower and lower. If you're powering a flashlight, this is just annoying as the beam becomes dimmer and dimmer. However, modern electronics are less forgiving about their power, and hate voltage fall-off. In the "best" case, they'll shut themselves off. Worst case, they'll start acting erratically or lock up. For all these reasons, ZC's are becoming hard to find in stores. Usually you'll encounter them supplied by producers of TV remote controls, cheap toys, etc. My advice. Throw them away (better: recycle them if your town does a hazardous materials collection) and put in some good alkalines.

2. Alkaline. You don't have to use acid for a battery electrolyte. Sorry to keep making you think back to chem class, but what's the opposite of an acid? That's right… alkaline. Well, using an alkaline electrolyte (instead of acid) makes all the difference. An alkaline battery uses the same anode and cathode materials as a plain zinc-carbon battery – but the alkaline electrolyte gives it five times the life and a flatter (better) discharge curve. Just as important, alkalines are much less likely to leak. Not perfect though. If the alkaline zinc-chloride electrolyte does leak out, it can still ruin your equipment. [Here's a tip: use ordinary white vinegar on a Q-Tip to neutralize the corrosion in your electronics. I've brought many a tape recorder, answering machine, and flashlight back to life this way].

Battery Shelf Life The ideal battery would keep its charge indefinitely while in storage "on the shelf." However all real batteries have a "self-discharge" effect, gradually losing charge even when not in use. Some people think keeping primary batteries in the refrigerator or freezer extends their shelf life. I haven't seen any hard scientific proof this is true, but it does make sense. Cold slows most chemical reactions, while heat speeds them up. But here's why I don't care. Reason #1: alkalines – even at room temperature – keep over 85% of full charge for at least 10 years. Reason #2: there's never enough room in *my* fridge…

3. Zinc-Air.StarTac Instant-Power These were the first button batteries, and are still popular for hearing aids. They've found new application as an emergency single-use power supply for your cell phone. They come in a sealed foil pouch. When you open the pouch, air activates the battery and it will keep your cell alive until you get back to civilization. Instant-Power. Not cheap, but some people will pay almost anything to avoid becoming unreachable…

4. Nickel Cadmium. NiCad's were the first, and remain the most common kind of rechargeable battery. They use a nickel cathode and a cadmium anode. That's a problem. You may not know this, but cadmium is a highly toxic metal. Ingest some and you're in big trouble. I'm not all that worried you're going to swallow an AA battery (although kids have been known to try), but there's concern the NiCad's thrown in the trash will end up in an incinerator or landfill. If your town has a battery recycling program (where I live it's called STOP: Stop Throwing Out Pollutants), please use it to recycle your NiCad and other batteries. Whole Foods Market, Ikea, and other some environmentally-sensitive retailers have collection barrels in their stores. Manufacturers such as Black & Decker have recycling programs for the specialized NiCad batteries used in appliances like DustBusters. You can also contact the Rechargeable Battery Recycling Corporation (RBRC) at 800-822-8837 for more info. The main reason why I don't like NiCads is their susceptibility to the dreaded "memory effect." I'm sure you've seen this happen: your electric shaver, DustBuster, camcorder, or cordless phone seems unable to hold a charge anymore. You'll take it off the charger and it'll run OK for a short while and then abruptly quit. That's the memory effect at work. If a NiCad is only partially discharged, then put back on its charger a few times in a row, it will "forget" how to hold a full charge. (For you chem class whiz kids who want to know why this happens: potassium-hydroxide crystals form inside the battery cells, blocking the chemical reactions and the flow of electricity.) There are two ways to prevent memory effect. One is to always let your device run all the way down before recharging it (a pain in the neck). The second is to get a "smart" recharger (like the Accumanager). A smart recharger or "conditioner" will automatically suck all the juice out of a NiCad before charging it back up again. Besides memory effect and toxic metal pollution, there's another reason to dislike NiCads: a crappy discharge curve. Even a new NiCad, fully charged, will only reliably give you back about two-thirds of its power. After that point, voltage drops sharply. Your digital camera, camcorder, or PDA will either quit suddenly, or perform erratically. Either behavior is unacceptable. Luckily, better alternatives are now on the market.

5. Nickel Metal Hydride. One of the first "advanced technology" rechargeables, Nickel Metal Hydride batteries (abbreviated Ni-MH, and pronounced "nymph" like the sea creature) are getting a lot of traction these days. They are superior to Ni-Cads in every way except two. They hold a better charge, last up to 40% longer, don't contain toxic metal, and don't suffer memory effect nearly as much. There are only two minuses: Ni-MH's cost a little more than NiCads and can only be recharged about 600 times compared to 800 or more for NiCads. For the chemists: NiMH's use a hydrogen-storing alloy metal as their anodes, a nickel oxide cathode. First available only built-in to higher-end electronics like PDA's and laptop computers, NiMH's are now available in common sizes like AA, AAA, C, and D cells. These can be recharged in the same "wall wart" recharger you've been using for NiCads, although a smart charger/conditioner like the Accumanager or AlphaPower BC-900 is better still. A conditioner has the smarts to monitor voltage while it's charging, and adjust the flow of electricity to prevent overheating/overcharging (which will dramatically shorten the life of your NiMH batteries). A good charger will also switch to "trickle" mode after bringing your cells to full charge. This tiny trickle of electricity will top off the batteries and keep them fully charged until you remove them from the charger. That's important for rechargeables, because all types have a much higher self-discharge rate than one-use batteries. This self-discharge effect is the main drawback of NiMH cells, and the main reason I don't put regular ones in flashlights or other infrequently used devices. Just a month on the shelf, and the unused batteries have already lost much of their charge. Nonetheless, NiMH's are great in digital cameras, PDA's, and other things you use all the time. I've even done surgery on my electric shaver, performing a "Nicadectomy" and transplanting a NiMH double-A cell into its guts.

6. Rechargeable Alkaline Manganese. Built with similar chemistry to regular alkaline batteries, these can be recharged about a dozen to two dozen times, although their capacity will diminish with each recharge. Nonetheless, they're sometimes a better rechargeable choice than Ni-Cads or NiMH's. That's because alkalines have a much longer shelf life and higher voltage (1.5v). They're a natural in flashlights, toys, radios, and other lightly-used items. You'll need a special, high-end recharger though, like the AccuManager. Whether you choose NiMH's or rechargeable alkalines, you are going to save a lot of money during the life of the batteries. They're more expensive to buy, but much, much cheaper in the long run. Throwaway alkalines cost about ten cents an hour (each) to use, but rechargeables can be renewed for only a penny's worth of electricity.

Eneloop7. LSD Battery. These are really far out man. Invented by Timothy Leary, these... wait. Strike that. Invented by Sanyo Electric Co. in 2005, these are next-generation nickel metal hydride batteries. Rather than lysergic acid diethylamide, LSD actually stands for "Low Self Discharge" and hold their charge far longer than regular Ni-MH cells. After a full year on the shelf, Sanyo's "Eneloop" batteries still retain 85% of their full charge, making them suitable for all sorts of applications you wouldn't have considered before: TV remote controls, clocks, and flashlights. They're also great in digital cameras, not only because they'll retain full charge longer, but also because of LSD's superior electrical performance in high current drain applications such as cameras and electronic flashes. For you techies, advantage is primarily due to a high-performance negative electrode "superlattice alloy." There's more to love about the Eneloop and similar LSD batteries from Duracell and Varta and others: environmentally-friendly composition and packaging, 1000 recharge cycles, and good low-temperature performance. The final great thing about LSD's is that they're sold pre-charged. Unlike other cells that must be charged for hours before first use, these are ready to rock right out of the pack. I think this new generation of "Ready-to-Use" batteries have removed almost every reason to keep buying disposables. Of course they're more expensive (initially), the ability to be recharged up to 1000 times means they're far, far less expensive in the long run, even if you amortize the cost of a nice recharger.

The High Environmental Cost of Disposable Batteries
We live in an age of renewed respect for the environment, but disposable batteries are NOT friendly to mother earth. According to Environment, Health and Safety Online, Americans purchase 3 BILLION disposable batteries annually! The average family uses 32 disposable batteries every year and almost every one ends up in the trash, making up 88 percent of the total mercury and 50 percent of the cadmium in the municipal solid waste stream. Ugh.

8. Gelled Lead-Acid. Lead AcidSame rechargeable technology as your car battery, but with a sealed or jelled sulfuric acid electrolyte instead of the open liquid acid sloshing around. They're old tech but still good for special applications. Most likely, the backup battery in your home or business alarm system is a lead-acid. So is the battery in your computer UPS (uninterruptible power supply). Lead-acid cells are very forgiving. They tolerate partial discharges without losing capacity (no memory effect), can be kept topped-off with a full charge with a simple (cheap) charging device, and come in big, powerful sizes. They're not available in "normal" sizes though; no AA's, C's, D-cells, etc. Please be sure to bring these to a recycler when they're dead and gone.

9. Lithium-Ion. I'm typing this article on a laptop computer powered by a Li-Ion (pronounced "Lion") battery. Lithium is a natural for power-hungry portable electronics. It's the lightest solid substance on earth. It's also the metal with the strongest positive emf (electromotive force) and therefore makes batteries with the highest known energy density (greatest amount of power per pound of weight). In a Li-Ion battery, the anode is plain carbon, the cathode is cobalt oxide, and the electrolyte is composed of lithium salts in ether. Manufacturers don't use pure lithium for a really good reason. It explodes. Pour plain water on lithium powder and KABOOM! You better go find a "Class D" fire extinguisher (for reactive metals) before things really get bad. A regular extinguisher like you probably have on the wall (Class "A" "B" or "C") is water-based and will just make the fire worse. Even manufacturing pure lithium battery cells is difficult and dangerous. If molten lithium comes in contact to the cobalt oxide cathode, you better stand back. Far back. Really far back. Understandably, most manufacturers play it safe and use "extracted lithium ions" instead of pure lithium. Somewhat less power but far more safety. If you hold a lithium cell in your hand, you'll be amazed at how light it is. The battery actually feels like a hollow shell, even though it packs more power than a heavy regular cell. Li-Ion batteries are commonly available in AA size and in 9-volt "transistor radio" size. The latter are sold as "super long-life" batteries for smoke detectors. But Li-Ion cells are available in many specialty sizes, like button batteries, and in machine-specific configurations for digital cameras and the like. They come in one-use or rechargeable varieties. As a rechargeable, modern Li-Ion's don't suffer from memory effect and are pretty forgiving of poor recharging habits. You'll find them in many high-end portable electronic devices sold these days: MP3 players, camcorders, PDA's, etc.

10. Lithium Polymer. LithiumPolymerA close cousin of the Li-Ion, the Polymer Lithium-Ion Battery (PLB) have a unique shape. They often look like a thin foil food package. But don't put a PLB in the microwave. Heat is their worst enemy. It causes them to swell up, with ruinous consequences. PLB's are composed of multiple dry film-like layers in a plastic or laminated aluminum foil package (instead of the semi-liquid constituents encased in a rigid metal can typical of every other battery described so far). This non-rigid construction using dry polymer electrolyte/separator films allows PLB's to be molded into a variety of custom shapes and built-in to smaller portable electronics (for example, the iPod).

Battery Technology Summary:

Technology Type Advantages Disadvantages
Carbon-Zinc Throwaway Very cheap Leak prone, low capacity
Alkaline Throwaway Ubiquitous, long shelf life Expensive to use
Zinc-Air Throwaway Good emergency battery Limited mostly to hearing aids
Lithium Throwaway Exceptionally long shelf life Very expensive to buy
Ni-Cad Rechargeable Least expensive rechargeable Memory effect, toxic disposal issues
NiMH Rechargeable Good balanced performance Can't be recharged often as NiCad's
LSD Ni-MH Rechargeable Long shelf life for a rechargeable A bit more expensive than Ni-MH
Gelled Lead-Acid Rechargeable Very forgiving of charging abuse Not available in common sizes
Rechargeable Alkaline Rechargeable Economical to use Requires special charger
Lithium-Ion Rechargeable High energy density Only found in high-end devices
Lithium-Polymer Rechargeable Powerful and compact Destroyed by overheating, expensive
Potato Battery Edible Tastes great Less filling

Bat Man

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