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December 14, 2009
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PoliceOne Staff How to Buy...
with PoliceOne Staff

How to buy batteries

By Tim Dees

Most of us are carrying electronic gadgets around with us, and they all require batteries. Battery form factors can be proprietary, as with most cell phones and laptop computers, or standard, as with most flashlights, cameras and recorders. Batteries also differ in the chemistries that make them work, and those chemistries largely determine their shelf life, endurance, number of charge-discharge cycles, and whether the battery has a “memory effect.” Knowing the difference between these chemistry types allows you to make a more informed decision when you buy batteries and the gear that uses them.

If you purchase equipment that uses a proprietary battery, that is, one made in a shape and power output unique to that gadget, you will be tied to a very limited collection of vendors when it comes time to replace the batteries. Some vendors will void your warranty if you use any batteries but the ones they supply. Most aftermarket batteries are reliable and less expensive than the OEM versions, but it pays to do some due diligence before you commit to a major purchase. The cost of using a battery that overheats and/or catches fire, leaks caustic chemicals, or refuses to take a charge after a few uses quickly wipes out any savings.

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Some battery chemistries are prone to a “memory effect,” where recharging the battery before it is nearly exhausted makes for a battery with greatly reduced capacity. 

We usually think of batteries in terms of their voltage, and certainly a battery has to put out the voltage and amperage appropriate for the device it’s powering. But the endurance, or capacity, of a battery is measured in watt-hours. A watt is the product of the voltage times the amperage, e.g. VxA=W, and a watt-hour is one watt of power delivered for one hour. You can expect the capacity of the battery to shrink as the battery ages and endures multiple charge-discharge cycles.

Battery technology has not kept up with the rest of the electronics industry. Cell phones are smaller than ever, but open the phone and you’ll see that half or more of its volume and weight are taken up with the battery. The push to bring an affordable electric car to market and a greater emphasis on “green” technology and recycling has driven the industry to intensify research on new battery chemistries.
Most batteries will use one of the following chemistries:

Lead-acid batteries are heavy, often contain concentrated liquid acid, are capable of delivering high voltages, and will endure many charge-discharge cycles. The most common application of lead-acid batteries is in gas-powered engines.

Zinc-carbon batteries are the “standard” variety that are now less common, now that alkalines are readily available. Zn-C batteries come in standard AA, AAA, C and D sizes and are usually cheaper than alkalines. They have less capacity than a comparable alkaline, and they have a propensity to leak and corrode over time, sometimes taking the device they’re in with them.

Alkaline batteries, the most common type sold in stores in size AA, AAA, C and so on, are usually Alkaline Manganese Dioxide. Historically, alkaline batteries were not rechargeable, but a relatively new formulation called Rechargeable Alkaline Manganese (RAM) allows alkaline cells to be recharged and does not have a memory effect. Do not assume an alkaline battery is a RAM formulation unless the label specifically indicates this. Recharging a standard alkaline battery can cause it to explode.

Zinc Air batteries are usually in “button” or “coin” form factors, common to hearing aids and wristwatches. They have an extremely long shelf life, losing only about 2% of their capacity per year, and supply a lot of power for their size. They usually have a paper seal that, once removed, causes the battery to discharge fairly quickly. It’s technically possible to recharge these, but for most applications it’s not worth the trouble.

Nickel-Metal Hydride batteries are commonly sold as rechargeables, often packaged with a charger that will accommodate multiple standard sizes. NiMH batteries have a reputation for limited capacity and losing much of their charge if not used immediately after recharging. New formulations sold by Sanyo and Duracell as Eneloop and Smartpower, respectively, come out of the package fully charged and will hold most of their charge for up to a year. They have capacities similar to alkalines of comparable size and will survive up to 1000 charge-discharge cycles.

Lithium batteries are supplied in standard AA and AAA sizes, but it’s more common to see them in smaller form factors, about the size of a thimble. They are used in devices with high intermittent power demands, like digital cameras and some flashlights. They have a shelf life of up to ten years, and deliver at least twice the capacity of a comparable alkaline. These are great choices for backups to rechargeable batteries in cameras and flashlights, when the rechargeables go dead and the devices they power are needed before fresh rechargeables are available.

Nickel Cadmium cells have large capacity, will endure about 500 charge-discharge cycles, and recharge fairly quickly (from 15 minutes to two hours). Their Achilles’ Heel is memory effect. A Ni-Cad battery that is repeatedly used for ten minutes and then recharged will become a ten-minute battery. The effect can be reversed partially (called “reconditioning”) by repeatedly draining the battery and then charging it to full capacity. Ni-Cads can also be cold-sensitive, refusing to deliver any power until they’re warmed up. They are still commonplace in rechargeable flashlights and some portable computers.

Lithium Ion and Lithium Polymer batteries are the most popular formulations for computer, cell phone, music player and electric and hybrid car batteries. They offer high capacity at a relatively low weight, will not develop a memory, and are tolerant of both low and high temperatures. They will endure up to 1000 charge-discharge cycles. They should not be overcharged, and get hot enough to cause a fire if they are crushed.
For mission-critical equipment like portable radios, budget long-term for replacement batteries when the originals have reached the end of their service life. You don’t want your troops’ radios dying when they’re in a tight spot. And ensure that all used-up batteries, regardless of chemistry, are recycled. Most chain hardware and electronics stores will accept batteries for recycling, free of charge.

Tim Dees is a retired police officer and the former editor of Officer.com and LawOfficer.com. He can be reached at tim@timdees.com.

About the author

PoliceOne Staff Reports feature contributions from our vast universe of subject matter experts. These sources include our own cadre of columnists as well as industry analysts, educators, and other noted specialists in their fields. P1 Staff Reports focus on an array of subjects including product reviews, product round-up features, “How to Buy” articles, and when necessary, product recalls and safety alerts. If you want to join our panel of experts, or have suggestions for topics we should cover here, please e-mail products@policeone.com with your feedback.



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