Batteries：Power On the Go! (2/2)
New varieties and more functions make batteries better

Rechargeables
Nickel cadmium
NiCad batteries have powered everything from cordless screwdrivers to emergency lights. However, they’re gradually losing their share* of the market because of one important problem: battery memory. If NiCad batteries aren't consistently drained to total emptiness before they’re recharged, they gradually develop a memory, taking less and less of a charge each time.
Nickel metal hydride
These are gradually being replaced by NiMH batteries, which cost more but don’t suffer from that problem. These are used for just about everything that takes rechargeable batteries, except high-drain electronic devices. Radios, portable power tools, music players, shavers and camcorders still use NiMH batteries. Unused, these batteries gradually lose power and if they sit longer than a month will probably need recharging.
Lithium ion
In gadgets in which you wan incredibly high power in a very small package, lithium ion is the current standard for rechargeable batteries. Cell phones, laptops and the like all come with Li-Ion batteries built in because they can handle the high-energy draws of these devices without weighing a ton. There’s also a newer kind, lithium-ion polymer*, which is lighter, cheaper and more rugged, so it’s starting to take over markets where weight is at a premium*. Lithium batteries hold their charges quite well.
Charge!
Don’t buy the cheapest charger you find; you’ll want one that quits feeding the batteries a full dose* of electricity once they’re fully charged. This prevents damage to your rechargeable batteries and makes them last longer. Also, look for a charger that’s labeled as having standby mode* or trickle charge* for fully charged batteries.
In general, it’s always a good idea to unplug a charger after a day or two if you’re not going to use the batteries right away. And never, ever, recharge non-rechargeable batteries; some can cause an explosion.

Vocabulary Focus
share(n)--- a part of something that has been divided between several people
at a premium (idiom)--- to be not common and therefore valuable
dose(n)--- a measured amount of something

high-drain(adj)--- referring to something that quickly uses up energy or resources
nubbin(n)--- a very small piece or bit of something
component(n)--- a part which combines with other parts to for something bigger

Specialized terms
polymer(n)--- 聚合物 a chemical substance consisting of large molecules made from many smaller and simpler molecules
standby mode (n phr)--- 待机状态 an energy-saving condition that saves power by shutting down unnecessary devices
trickle charge (n phr)--- 慢速充电；细流充电 a slow restoring of power to a battery at a continuous low rate to keep it in a fully charged state

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