Lifespan of battery...

How long is the average lifespan of a battery if you use the laptop every day on battery for, say, 3 hours or more? Why I ask: if it can last some 4 or 5 years or more, then I'd get rid of the extra one I have; but if it will die within 2 years, then I'll keep both. Any advice appreciated.

 

After about 300-500 cycles the battery will be at 50 percent of "new capacity".

 

Chances are, with that usage, it will lose most of its capacity within 2 years.

 

It depends on how many cycles you make.

If you have a T400 and you empty your 4 cell battery every day with that 3 hours of use, you get a cycle per day. That way the battery will probably be rubbisch after two years.

If you a X200s and you empty your 9 cell battery only for 33 percentage points every day, you only get 100 cycles per year. That way it will easily get to two years, be it with a loss in capacity.

And then it also depends on temperature:

If you store your battery on top of your home's heating system, it will loose capacity rather quickly at 60 degrees Celsisus.
But if you store it in your refrigerator at 0 degrees Celsius, it will loose only a very small part of it's capacity.

And besides that and time, it also depends on level of charge:
The lithium batteries used in the ThinkPads these days are best off with a ~40% charge. At 100% charge (like most guys that use it as desktop replacement have) it looses capacity rapidly. Storing it at 0% charge is also VERY bad for it's capacity. ~40% is the optimal charge level.



To summarize: these batteries loose capacity because of these four factors:
1) Time
2) Temperature
3) Cycles
4) Charge level

1) cannot be tampered with by humans
2) keep temperature above, but close to the freezing point to minimize this effect
3) Use it less to minimize this effect. Buying a 9 cell while you strictly seen only need a 4 cell works for this.
4) Keep it around 40% charge. Again: if you only need a 4 cell, but buy a 9 cell this is easier, because a 30Whr battery would be drained from 100% to 0% for 30Whr and a 90Whr battery could be set to only drain from 60% to 27%.

If you don't use your notebook on the go in the summervacation: charge the batteries to 40% and put them in a moisture-tight bag in the refrigerator. Storing them at 100% charge in a hot computerroom will do A LOT more damage.

Also see wikipedia:
http://en.wikipedia.org/wiki/Lithium-ion_battery

Also keep in mind that the more capacity your battery will loose, the more cycles it will make per hour used. If you have a new 80Whr battery and use it between 70% and 20% charge each day and then charge it back up to 70% you get half a cycle each day.
If this battery looses half of it's capacity you now discharge it between 100% and 0% to get the same 40 Whr, making one cycle a day.

 

Thanks for the information. For a 6/8/9 cell battery, if it has some 40% charge left after today's use, is it better to continue using without recharging tomorrow, or to add to the 40% so that it will never/seldom discharge to below 40%?

 

It's better to charge it back up. Lithium batteries love the partial discharges / charges.

Once in two months or so I would charge it to 100% and then discharge it to 0%.

Lithium batteries are different from NiCd batteries: NiCd batteries need to be used from 100% to 0% before recharging otherwise they loose the capacity of the unused part.

 

I'm approaching 250 cycles on my 16 months old 6-cell X300 battery . I usually fill up both batteries to 100 %, bring the laptop to university, drain the batteries to 0-1 %, and then recharge it. Three months ago when I got the laptop, the battery had around 170 cycles and could store 82 %. The Ultrabay battery was brand new, with 0 cycles, now has 50 cycles.

In Power Manager, I can view the full charge capacity of both batteries, and they're now at 99 % both. If there's any conclusion to draw from that, it's that batteries should be discharged completely regularly, and not stored at 100 % charge. At many companies, the laptops are plugged in all the time, and having the batteries at 100 % charge all the time puts on more wear on the batteries.

 

What is the current full-charge capacity of your Ultrabay battery now? Mine is at 39% of new capacity after 71 cycles.

 

Can share some data from a unibody MacBook. Have been using it on battery almost daily for 10 months. Its health is at 96 %, with 330 cycles. I quite often let it empty itself completely.

 

My experience has been that new batteries start to decay noticeably after less than 5 months use (I tend to run the battery most of the way down about every other day). I was getting about 4.5 hours of runtime on my x200s with 6-cell when the battery was new...now 5 months later it's down to about 3.5 hours max.

 

That is quite low battery life for an x200s.