THE GOODS : Running on Empty? : If you don’t buy them now, you’ll regret it come Christmas Day. Because, trust us, you are going to need batteries--and lots of ‘em.

The holidays are coming, and with them a dreaded annual purchase. No, not fruitcake. Batteries.

Technology has launched a new tradition, one in which batteries have become as entrenched in the festivities as gift-giving. For lights, for cameras, for the proverbial noisy toy. Hard as every parent tries to extol the virtues of Lincoln Logs, the kids probably want Missy Wah-Wah, and that crybaby needs juice.

If you don’t buy them now, you can fish around in that catch-all drawer, but you’ll likely have only one of each kind, probably spent. You can pull batteries out of something else, then curse the decision months later when you realize your portable radio batteries are in your kid’s walkie-talkie.

Or maybe this is the year you’ll invest in rechargeable batteries, spending a little more in the short run but saving hundreds in the future--all while doing the earth a good turn. Then there are those pricey batteries for your video camera; costing at least $35 each, it’s tempting to just see the celebration live.

Americans purchase more than 3 billion AAs, Cs, Ds and 9-volts annually--many of them bought between now and Dec. 26.

There are two kinds of batteries: primary and secondary. Primary batteries are disposable, made of alkaline, zinc-carbon or lithium. The battery unit itself is often referred to as a “cell.” A single alkaline cell is about 1.5 volts, the equivalent of one AA battery. Prices vary, from $2.39 for two AAs (Duracell and Energizer) to about half that (for Eveready).

Cs, Ds and 9-volts follow suit, with Duracell and Energizer the more costly. Because of problems with toxicity in the nation’s landfills, most batteries are now mercury-free, as manufacturers are quick to tell you on the package.

“Disposable battery companies are touting the ‘0% mercury’ claim because of pressure from an eco-conscious public,” said Doug Pratt of Real Goods, a mail-order company in Ukiah, Calif., that specializes in ecologically conscientious products. “But that still leaves 3 billion metal cases just rusting away in landfills. That’s an enormous amount of resources we’re throwing away.”

Made without toxic materials, such as lead, most rechargeable batteries rely on nickel cadmium for their power. At Real Goods, AAs list for $2.25 each and if charged once a week, will last 19 years. You’ll need to buy two sets, however, unless you are willing to live without batteries while they recharge, which takes an average of five to eight hours. You can also buy “nicads,” as they are called, at stores for about $6 for two AAs.

You’ll also need a charger. Real Goods carries several, from the $14 solar charger, for AAs only, to a $59 Eco-Charger. You need to charge new rechargeable batteries before use. Because they self-discharge over time, they are delivered “dead.”

You can also use a charger to recharge disposable alkaline batteries “about five times, after which point they drop to about 20% of their initial capacity. But they can still be recharged another 30 or 40 times,” Pratt said.

“Batteries need to be charged often, not only when it’s your birthday or a party,” said Carlos Marquez of Samy’s Camera in Los Angeles. “When you don’t use the battery, you have to leave it fully charged. But after a month or so, it dies anyway. It’s like leaving your car in the garage for a week. You come back, it’s dead, you need a jump. It’s the same with batteries. You give it a proper charge often, it’ll last three or four years.”

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All video cameras rely on rechargeable batteries; the charger and battery are included in the price of the camera. But video camera batteries do not last long, and you need, at a minimum, two: one to use while recording, the other to be recharging. Prices depend on how much amperage you buy, usually from $35 to $130. The higher the amperage, the longer the battery runs, though none run longer than about 1 hour 45 minutes.

Until recently, you needed to run down a video camera battery’s “memory,” or charge, before you could recharge it. “You can’t use the battery for 10 minutes, then try to stick it on the recharger. It won’t take the charge,” Marquez said.

This year, many companies introduced an improved, “no memory effect” nicad, which means you don’t have to use up all the juice before you recharge. There are also a wide array of chargers, as well as DC adapters that fit around your waist or into your car’s cigarette lighter, into which you can attach your video camera’s battery pack, lengthening the life of its charge.

But what if you’re a bonehead who goes to Disneyland with two fully charged batteries that both run down? “There’s something called a Dummy Box,” said Marquez, holding what looked like an empty cassette case. “You open it up, stick six AA batteries inside, and voom, shoot for another half-hour.”