Care and Feeding of Batteries

by Bob Seidel

Before I start this week's topic, I need to discuss the recent hoax e-mail going around that attempted to inform people about a new virus and had them erase a supposed virus file that was in fact critical to Windows. The good news is that a number of my clients and friends actually forwarded this to me and asked my opinion before erasing the file. The bad news is that thousands of people around the world didn't check and crippled their systems. Let me make this very simple.

First, get a virus-checking program - either Norton or McAfee. Second, install it and update the virus definitions frequently. Having done that, IGNORE ALL E-MAIL concerning viruses - throw it away and don't forward it to your friends. Even if the e-mail doesn't contain a virus itself, or isn't a hoax, its probably out of date anyhow. Just throw it away. Please.

Now, on to batteries. In this column, I am going to specifically address rechargeable batteries used in digital cameras, portable music (MP3) players and the like.

There are basically three types of rechargeable batteries in common use today. NiCd (Nickel-Cadmium), NiMH (Nickel-Metal-Hydride) and Li-Ion (Lithium-Ion). They all have different internal chemical processes, are used somewhat differently, and have different charging requirements. If your camera or player uses standard AA size batteries, you will probably be using NiCd or NiMH. I do not know of Li-Ion batteries in the AA size. If your device uses a custom size battery, or perhaps an internal non-removable battery, you will need to find out (usually from the User's Guide or device instructions) what type it is.

NiCd (nicad) batteries were the first common form of rechargeable battery. They work very well in digital cameras because they have a low internal resistance, which enables them to deliver a lot of current (power) quickly. There are two significant drawbacks to nicads. The first is that they exhibit something called the "memory effect". Without getting too technical, memory effect limits the amount of power a battery can deliver if it is not fully discharged and then fully charged. To eliminate memory effect, you should always discharge nicads fully (down to about 1 volt per cell) and then charge them completely up after that. Or, saying it another way, you should NOT continuously charge nicads - work them hard and then recharge them fully. Nicads also have a limited number of times they can be recharged; you can do it many times but they won't last forever..

NiMH batteries do not have the memory effect - or, at least, it is small enough not to be a practical problem. You can recharge NiMH batteries without running them down - it does no harm. No harm, in this case, meaning it does not limit the amount of power that the battery has. But, like nicads, you can only charge them a certain number of times. So, you can recharge NiMH batteries often, but you are still using up some of its life by doing more charge cycles. Bottom line here: its OK to put your NiMH cell phone into its charger every night.

Li-Ion batteries are usually used only in special devices, such as laptop computers. Their chief distinction is that they can be charged quicker than other batteries, if the charger has built in circuitry to properly do this. Li-Ion batteries also do not exhibit the memory effect, so you can leave your laptop plugged in to the wall a/c socket when you are home.

Perhaps more important than knowing the type of battery is knowing the type of charger that comes with it. Basically there are two types of chargers: fast or smart chargers that can charge batteries in four hours or less, and overnight or trickle chargers that require 8 hours or more to charge. You can usually leave batteries on slow charge without damage or danger - if you have a NiCd rechargeable flashlight that plugs into the wall, you can usually leave it there permanently so it is ready if a power failure occurs. On the other hand, you should NEVER leave any type of battery in a fast charger past the time that the charging LED on the charger indicates that it is finished. Of course, in all cases, it's best to follow manufacturer's directions.

(Bob Seidel is a local computer consultant in the Southport / Oak Island area. You can visit his website at www.bobseidel.com or e-mail him at bsc@bobseidel.com).