How long to keep battery fully charged without shortening its life?

So it's said that when you don't use a battery for prolonged time it's better to keep it at 40% charged. My question: how long storage time would make this necessary?

For example, suppose my battery is 100% charged now, and I don't plan to use it for 1 week, 2 weeks, 1 month,... should I discharge it now to 40% then put it aside? Does it make difference for a coulpe weeks?

 

In my experience it hasn't made much of a difference. I leave my dell plugged in all day everyday for the past 1.5 years and when I take it off I still get the same ~2 hours I did when I first got it.

 

Either way, the battery cells degrade over time with or without use. It's generally up to you on how you think the battery will last longer.

I keep the battery installed on the laptop all the time.

 

I recommend using the charge thresholds (advanced tab in power manager). These are a very effective way to keep the battery at a middle range, and thus preserve long life, without the hassle of having to remove the battery.

 

does my SL400 support this feature? i'm using the latest power manager and i don't see this option anywhere (yes i'm in advanced mode)

 

I'm not positive about the SL as they are kind of the odd duck of the ThinkPad line. However, if it does have the feature it is in the following place.

1. Open Power Manager
2. Switch to advanced view
3. Switch to the battery tab
4. Click Battery Maintenance
5. Set your thresholds here (I use 50-95% on average).

 

I have used a battery for almost 5 years, 95% hooked to the mains, and battery works just as the day it was born. I did the same with my previous laptop and battery. Just plug into the mains as much as you can, and don't worry. The battery is basically an Uninteruptible Power Supply Unit built in. It is there when the mains is not there or interupted.

 

Everyone saying your laptop battery is just the same as you got it x-years ago is being a little disingenuous.

The battery will degrade. You can just make sure to not expose it to continual heat, or repeated top-offs.

Just avoid the usual abuses and you can keep the life of the batteries going for a couple years.

 

Thresholds are a nice feature, that's for sure. You can set your laptop to stop charging when battery level reaches certain point and do not start charging again until it goes down to a certain point. The only problem with it is that it won't start charging until the battery goes down to a certain point...

Like if you need full battery and the battery is in the middle between your charging/discharging levels... Are you going to have to wait for it to discharge first to start charging again... ? I suppose you could readjust thresholds...

Just a loose comment, something I was thinking about when I saw this thread...

 

Basically I was going for a non scientific real world result thats all. My battery gets the same now as it did when I got it and its been plugged in about 90% of its life(and its running 24/7. I know that a battery will degrade over time, but mine has not yet so I feel 100% confident with my post.

 

Your battery is exactly the same capacity as received after a couple years? Not does it appear to show the same amount of battery life. It actually has the same capacity (wHrs shown in the power manager)? Also have you readjusted your battery gauge periodically?

 

No adjustments, no tweaks. Just plain old watching a clock to see if it matches the estimated time. When my dell says it will get 2 hours its pretty spot on.

 

yea then i guess the SL line is really the odd duck of the ThinkPad line... here's what i see:



this is the latest power manager v2.43 that i got from the lenovo support website