Portable electronic equipment has a hidden operating cost. You wont find it listed on the price tag, or mentioned in the advertising, but by the end of a year of use, you may well have matched the cost of the component with what youve paid for batteries to keep it running.

Batteries arent cheap, and keeping a fresh supply on hand can result in operating expenses of five dollars a week to five dollars a year, depending on the component they power. There are some ways to keep battery costs at a minimum, and they should be kept in mind when shopping for components.

The first question you should ask yourself is whether the component you plan to buy needs to be battery operated. Many portable radio-cassette-TV combinations are designed to run on either batteries or household AC current. For indoor and at-home use, it. is cheaper to plug the unit into the wall, even if it makes the component less convenient to lug around the house. Many smaller cassette machines and radios have adaptors, often sold as an extra, that allow the user to bypass the battery power for AC wall power. These adaptors are actually AC/DC transformers, and even if your unit doesnt come with one, your local electronics shop may well be able to supply you with a battery eliminator."

If you use an AC adaptor in a batterypowered device, always plug the adaptor into the component first, then plug the adaptor into the wall outlet. It isnt a good idea to leave the adaptor plugged into the wall when the unit isnt in use, for although the adaptor is UL approved, it can overheat and destrtict. If anyone tells you that cant happen, have them call me. Ive had adaptors melt down during normal use, discharging a flow of noxious chemicals all over the floor.

If the unit does use only batteries, make sure the batteries are easily available* and replaceable. This is especially applicable to pocket calculators and digital wrist watches. Often new models will use very small batteries that arent in stock at every, drugstore (Ive spent two or three days at a time going from store to store trying to find replacement batteries for some devices). These more exotic batteries are usually expensive as well. Also, some of the smaller digital watches require a special tool to replace the batteries in the watch case which means you cant do it yourself and there is a charge by whoever does it. (I just threw away a Casio digital watch-calculator because after going to several stores who wouldnt/couldnt replace the batteries, though in some cases they sold the watch, I tried to do it myself and failed.)

When you buy replacement batteries, make sure theyre fresh." Batteries have a shelf-life, if theyve been sitting in the store too long, they may not supply the amount of power youll get from new batteries. Thus it is always best to buy new batteries at a store that sells a lot of batteries and is constantly replenishing their supply.

Dont buy cheap batteries; they wont last as long as the more expensive ones. And stick to name brands, avoiding bargains, which will turn out to be a waste of money. Many battery manufacturers list their battery types and suggested usages on the back of the packages the batteries are sold in. Believe them. It is also advisable to avoid cheaper alkaline batteries and go for the costlier ones.

Rechargeable batteries, usually nicad" batteries, do work and can be recharged with the proper recharging device, but there are catches. First, it is time consuming to recharge these batteries, so you have to plan ahead. Second, these batteries have what is known as a memory." If theyre supposed to last say two hours for every complete recharge, and you dont recharge them completely (this may take up to 14 hours), theyll forget" what their full charge is and never operate at full charge again! Third, even rechargeable batteries hjave a set life. They can only be recharged so many times before they stop functioning. Manufacturers get around this point by claiming their batteries can be recharged hundreds of times" or up to a thousand recharges."

When using rechargeable batteries, dont over-charge them, at the least over-charging them (leaving them in the recharger too long) will ruin them, at the most it will cause them to explode. Many recharge devices have a special safety circuit that will stop the recharge process when the batteries have been recharged.

Solar cell power is available for many devices these days. There are watches, radios and calculators that use solar power cells instead of batteries. Also, Edmund Scientific now sells an under $20 solar panel with a set of adaptors to power iust about any battery-operated device. $20 isnt much, when you .consider how much you spend on batteries each year.

Batteries last longer when theyre used for short periods of time then allowed to rest. This means youll get more power, or mileage as it were, out of your batteries if you use the component for a half hour, shut it off for a while, then turn it back on. Leaving the component on constantly for very long periods of time will run down the batteries very fast indeed. This is especially true with battery powered TV sets and other high-voltage devices.

Finally, some devices use more battery power than others. For instance, there are two types of digital watches and calculators: those with led (light emitting diodes) displays and those with liquid crystal displays. The liquid crystal displays use a great deal less power and will not require new batteries as often as the led displays.

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