SThe biggest chokepoint in technology is a single roadblock: batteries. Amidst all of the amazing advances in the last 50 years, battery tech has remained fundamentally unchanged, engineers incrementally squeezing out a few extra drops of power from old tech each year. With better batteries, you wouldn't just be able to make it through the day with your iPhone 3G on a single charge, but laptops and phones could run faster, electric cars would rule the highways-it'd be like a brand new world. There are like a million different kinds, but here's a rundown of the most common ones we're stuck with in gadgets for now, and their strengths and weaknesses.Pretty much all batteries basically work the same way: Chemicals packed inside get freaky and produce electrons, which pool up on the negative end of the battery, essentially turning chemical energy into electrical energy-when you connect a battery to a gadget, the electrons run through the gadget and back to the positive end of the battery, completing the circuit and causing the chemical mojo that produces energy, making your toy robots go go go. The differences between various kinds of batteries come from the different chemical cocktails inside, which they're all named for-like your favorite actual cocktails, each one has its properties, making it good for some stuff and not others. Alkaline are the classics-they powered your Game Boy for 20 solid minutes of fun (or 2 1/2 on a Sega Nomad)-they are cheap and disposable. Energy density, the amount of power packed in the space, isn't bad, but with a demanding, high powered gadget like an MP3 player or digital camera, they die quicker than morbidly obese Mississippians parked in front of an all-you-can-eat biscuits and gravy trough. With lower power gear, they're decent enough, as years of use and abuse have probably told you. Biggest suckpoint, as you Wii owners know, is that they're not rechargeable. Silver oxide or silver-zinc batteries pack a good bit of power inside and last a loooong time, so they're the most common battery in watches and small toys—not to mention torpedoes and submarines, or other applications where performance matters more than cost. The downside is that the silver makes them expensive if they're bigger than the button size for gadgets. Oh, and the mercury leakage issue at the end of their life is kinda uncool. Lead-acid batteries have two major types: a starting battery, like the one in your (gas-guzzling) car, which is designed for short power jolts, and a deep-cycle battery, which delivers a lower, more steady power level, so it's used on boats, campers, golf carts and backup power in various gadgets. Rechargeable Alkaline: Surprisingly similar to regular 'ol alkies, they're slightly tweaked to take recharges-which means giving it some juice pumps electrons back into the battery. They don't self-discharge like the more popular nickel metal hydride batteries, but their capacity falls off with every recharge and doesn't quite match regular alkies. You don't really see these at Wal-Mart, if that tells you anything. Nickel Cadmium, aka NiCads, some of the first decent rechargeable batteries, and still among the cheapest, so they were popular in toys and other gadgets. They recharge fairly quickly and will take a beating, but the memory effect (a recurring issue with rechargeables) is nasty with these-if you try to recharge it without using all the energy, large crystals build up that limit how much power it'll pump out next time to however much was used before you recharged it (like it "remembers"). Also, they'll leak out all their power after about 90 days, so you don't wanna leave them on your shelf or in a charger for a long time. SNickel metal hydride, aka NiMH, replaces the cadmium in NiCads with an alloy that makes it hold more 40 percent energy in the same space than NiCads. Memory effect issues aren't as severe, but NiMH are kinda finicky about recharging/discharging. Still, do they well with the systems in hybrid cars, so giant packs of them are what's in current hybrids. They're not bad substitutes for alkalines either in terms power/space/price and hold up well to high drain from gadgets, so they're the most common kind of rechargeable you'd buy at Wal-Mart for your Walkman or something. SLithium ion aka Li-ion set the gold standard in a gadget battery and are a major bump in energy efficiency and density from nickel-based batteries while not suffering from by the dreaded memory effect. On the other hand but they're not as thrashable and have that whole infamous propensity for explosion (really, it's only a few per million). Another major issue with them is that if they're spent too hard and drop below a certain voltage, its energy capacity can be permanently lowered, so they're designed to shut off whatever they're plugged into after a certain point. Little advances allow researchers and scientists to wring modestly more power out of it ever year. Basically, if you've got a gadget with a rechargeable, it's probably one of these, or, increasingly, a li-poly battery (see below). SLithium ion poly or lithium poly or li-poly, sprung out of lithium ion (obvs), but uses a gel polymer-based electroltye—hence the name. They're more durable (less explode-y) than standard Li-ion, plus they're lighter and can be molded into whatever shape you want, so it's not surprising you're seeing them replace lithium ions in laptops and other gadgets, like the the iPod. One issue is that they do wear a bit more quickly than regular Li-ion, but that's getting better. SLithium iron phosphate is another spin on lithium ion that replaces the cobalt oxide mix in li-ion. Advantages are that it's less likely to go boom and it can discharge and recharge incredibly quickly. But until now, they've been expensive and kinda complicated to make. Mostly famously, it's in the OLPC XO Laptop, but is on its way to a hybrid car near you. And that just about covers where we are now with portable gadget power. Feel free to wax philosophically on other battery banter in the comments, but we'll be covering what's around the corner in a future Giz Explains installment. Something you still wanna know? Send any questions about touching, feeling or screening to firstname.lastname@example.org, with "Giz Explains" in the subject line.