Batteries are a must on most holiday shopping lists -- and a mini-disaster if they're forgotten. Realizing, too late, that the talking bear won't talk without them can spur a mad dash for an open store that sells batteries -- and still has some left to sell.

Even under less stressful circumstances, selecting the best batteries for your needs can still be a hit-or-miss proposition. Many manufacturers recommend alkalines because they last a long time. But they're expensive -- more than $1 each for D-size batteries.

Would cheaper general-purpose or heavy-duty batteries work as well in some situations? Do rechargeables really save money? Does any one brand last longer than others?

The engineers at Consumer Reports say that although there are obvious differences between types (alkalines last longer than heavy-duty models, which outlive general-purpose models), there usually isn't much difference among brands.

To answer the other questions, the engineers tested 4,000 battery samples of eight brands in the sizes people use most: AA and D.

You'll be sure to get your money's worth if you buy only alkaline batteries. All the alkalines tested outlasted the other types. You can expect to pay about 75 cents for the AA size and about $1.15 for the D. But shop around. Prices vary from store to store by as much as 50 cents per battery.

Two brands of heavy-duty D batteries -- Radio Shack (55 cents) and Panasonic (68 cents) -- lasted significantly longer than others of their type in both continuous-use and intermittent-use tests. And the Radio Shack D batteries were so inexpensive that they would cost about the same to run as alkalines. The only catch is you'll have to replace them more often than alkalines. Among heavy-duty AA batteries, Radio Shack's 39-cent battery was the cheapest to use.

Rechargeable batteries can pay for themselves in a few months in devices you use frequently, such as a walkabout tape player. AA-sized rechargeables are particularly practical because they last as long as or longer between charges as a heavy-duty battery. But they still last only a third as long as an alkaline battery. All of those tested performed equally well (provided the slightly lower voltage of the rechargeables suits your application). At $2, the Radio Shack AA battery was a bargain.

Most rechargeable D batteries had a brief life between charges. You'd be recharging them more than you'd be using them. The Radio Shack 23-140 is an exception: It lasted twice as long as the others. But it's twice as heavy and, at $7, twice as expensive.

A battery may look innocent, but it generates enough power and contains enough corrosive chemicals to be hazardous. Don't let batteries accidentally touch anything metallic (including the keys and change in your pocket and tools in your hardware drawer). Metal can short out a battery, generating enough heat to burn.

Don't try to recharge batteries that aren't made for that purpose. Keep batteries -- especially the small button variety -- away from children. And don't burn batteries or put them with trash that's headed for the incinerator. They can explode.

Keep general-purpose and heavy-duty batteries in the refrigerator. They'll last longer. Alkalines keep nicely at room temperature. But don't store them where they'll get too hot -- near a radiator or a stove, for example.

Change all the batteries in a device at the same time. A set of batteries will produce only as much power as the weakest battery will allow. Furthermore, the strong batteries will put extra stress on the weak ones, possibly causing them to leak. For those same reasons, don't mix batteries of different types.