More About Li-Ion Batteries

 

How long does a Li-Ion battery last?

Most cells in Li-Ion battery packs are set to be fully charged to 4.20V/cell and typically lasts  300–500 cycles. If they are only charged to  4.10V/cell, the life can be prolonged to 600–1,000 cycles.

 IF you used it fully every day and had to recharge it every day - that would mean it would last between 8 months and 1.37 years.

A couple I looked at recently are guarantied for 18 months...

I own a cheap compact unit from Black & Decker that I keep on the charger all the time (something you're not supposed to do - instructions say not to leave it on the charger for more than 30 days without use.) and it's still going strong after about 3 years. (I hardly ever use it, - just around the house)

Some batteries in industrial instruments are date-stamped, indicating the life expectancy, but most quality packs will last considerably longer than what the stamp indicates.

Most packs last three to five years.

What About Charging Li-Ion? 

This type of rechargeable battery does not have or develop a memory as people are often led to believe.

A Li-ion battery does not need periodic full discharge cycles to prolong life like the NiMh battery does.

A battery dwelling above 30°C (86°F) is considered elevated temperature and will reduce the life expentancy.

Even more stressful is leaving a battery in a hot car, especially if exposed to the sun.

Li-ion does not need to be fully charged, as is the case with lead acid, nor is it desirable to do so. In fact, it is better not to fully charge, because high voltages stresses the battery.

Li-ion should not remain at the high-voltage ceiling of 4.20V/cell for an extended time. When fully charged, remove the battery and allow to voltage to revert to a more natural level.

Li-ion should never be discharged too low, and there are several safeguards to prevent this from happening. The equipment cuts off when the battery discharges to about 3.0V/cell, stopping the current flow.

To prevent a battery from falling asleep, apply a partial charge before a long storage period.

Not fully charging a Li-Ion battery to it's full voltage threshold, prolongs battery life but reduces the runtime. Since the consumer market promotes maximum runtime, most chargers go for maximum capacity rather than extended service life.

Check before you buy, some newer Li-Ion batteries can be recharged in 30 minutes!

In a nutshell.. 

The use of Li-Ion batteries is actually very young and is an intermediate step and still evolving with a few minor problems, like not running  or charging in very cold weather, stopping for no reason...then recharging back to full capacity in a couple of minutes, etc.

For those who occasionally use their tools, it may be best just to settle for Ni-Cad powered tools as they are harder to damage than other types and will endure deep discharges for longer periods. The Ni-Cad battery is excellent for long-term storage, and in most cases stored fully discharged. A Lithium-Ion battery, in comparison, will be permanently damaged if stored in discharged state.

For active DIY ers and professionals that use their tools on a daily basis, the Lithium-Ion battery is currently the best choice, since it has more life cycles and will provide your cordless tool with the maximum power it needs. It charges fairly quickly to keep you working for a long time before it will run out of power.

If you need more info - check out what wikipedia has to say..