the laptop battery technology

the laptop battery technology

Most laptops now use lithium ion (LiIon) batteries. LiIons should be managed differently from the NiCad or NiMH batteries used in older laptops. In particular, LiIons should not be run all the way down to prevent "memory effect". First, they don't have a memory effect, and second, running them down tends to reduce their capacity. If the laptop does not need the battery it should be run to about 40% charge and stored in a cool place. LiIon batteries go bad whether used or not, so only buy new LiIons. Typical life is 2-3 years.

Why are iBook and Powerbook batteries so expensive? Part of the reason is that LiIon batteries can do bad things if they overheat (creation of Lithum metal which "burns" in water, chance of fire). So LiIon battery packs have an internal circuit to prevent overcharging (which would cause them to overheat). There can be several functions for the protection circuit, including shutting it down in case of over charging, when the voltage drops to a predefined level, or if it thinks the battery is otherwise damaged.

Problems with the power circuit can cause a "good" battery to shut down. The recent post about fixing iPod batteries likely had to do with re-setting something in the battery protection circuit that caused it to shut the battery off early. Isidor Buchmann's Batteries in a Portable World site talks about methods some have used to try to reset the protection circuit on batteries that seem to have died young.

Trying to reset a LiIon protection circuit is dangerous to try yourself - you could end up with a nasty fire. Plus the electrolyte is flammable and caustic, so it needs to be well packaged to make a spill unlikely, even if you do manage to overheat it. All this costs, which helps explain the price of the batteries...

Simple Guidelines:
Charge the Li-ion often, except before a long storage.
Store at about 40% charge in a cool place
Avoid repeated deep discharges.
Keep the Li-ion battery cool.
Prevent storage in a hot car.
Never freeze a battery.
If your laptop is capable of running without a battery and fixed power is used most of the time, remove the battery and store it in a cool place.
Avoid purchasing spare Li-ion batteries for later use.
Observe manufacturing date when purchasing.
Do not buy old stock, even if sold at clearance prices.