All batteries eventually lose the ability to hold a charge. A dead laptop battery not only grounds users that want to be mobile, but replacement batteries are fairly expensive. So, kudos to Samsung for pro-actively dealing with this on one of their laptops.
I say this because someone using a relatively new Windows 7 based Samsung notebook recently asked me how to respond to a question that popped up on the screen. The system was offering to only charge the battery up to 80% of its capacity. What's up with that?
This is a good thing, maybe even a great thing, for someone who normally keeps their laptop computer plugged into electricity. It turns out that the lifespan of Lithium Ion batteries decreases when they are constantly charged to full capacity.
Most battery damage occurs when the cells inside are at or near capacity. That’s because batteries get a bit hot under the collar when they max out their charge at 100 percent. This heat causes the delicate structures within to start to break down, which ultimately makes the battery less capable of holding a charge. Eventually capacity drops to the point where the battery won’t hold a charge at all and it has to be replaced.
But they have software that offers a solution:
One of the key features of PowerPlus is a simple setting you’ll find on your Samsung laptop called Battery Life Extender. ... Here you’ll find the option to either leave your battery in Normal mode (which lets the battery charge to 100 percent of its capacity) or engage the Battery Life Extender mode, which caps the charge at 80 percent. Battery Life Extender helps keep the battery from overcharging and overheating, which protects it from being damaged. The result is a battery that keeps on going for years.
When a Samsung laptop owner wants all the horsepower their battery has to offer, they simply disable Battery Life Extender mode and the battery will charge up to 100%.
The obvious downside here, is that when the need for an extended run time comes without warning, the battery is only partially charged. On the whole, this seems like a fair trade-off to me.
I use a Lenovo ThinkPad and this sent me digging into the settings offered by the pre-installed ThinkVantage Power Manager software. Sure enough, Lenovo offers a similar option, something I had overlooked when first configuring the machine.
The Lenovo help files offer the same advice as Samsung:
If you primarily use your computer with the AC adapter attached and only infrequently use battery power, battery deterioration may occur faster when the battery is constantly charged at 100%. Lower the charge thresholds of your battery if you use your ThinkPad computer often while on AC power.
I missed this initially for two reasons. For one, the appropriate setting is buried deep in the Power Manager (version 3.30) user interface. Then too, there are terminology issues.
One group of front and center settings in the Power Manager interface offer "Battery stretch". This has nothing to do with stretching the lifespan of the battery, instead it refers to stretching the current charge, by doing things like dimming the screen. There are also settings for "Maximum Battery Life" which, again, refers to life of current charge.
ThinkPad owners should go to the Battery Information tab and click on the Battery Maintenance... button.
The important section of the resulting window is shown below
Lenovo's documentation is, frankly, poor. My guess is that it was written for a different version of the Power Manager software.
By default, Automatically optimize for battery lifespan is selected. This option sets the battery charge mode automatically by monitoring battery usage. Initial mode is Maximum Runtime mode and this option charges with full charge voltage. When the battery charge mode is set Maximum Lifespan mode, it helps to increase battery lifespan by reducing charging capacity. When Maximum Lifespan mode is set, Power Manager’s battery gauge displayed on taskbar is shown with green outline. Always fully charge (Start when below 96%; stop at 100%) uses Maximum Runtime mode. This mode starts charging when the remaining capacity of the battery is below 96% and stops charging at 100%. Note, this setting may not help to increase battery lifespan.
Despite what the documentation said, my laptop had defaulted to "Always fully charge".
I changed it to "Optimize for battery lifespan," and then ran a test. With the battery drained to 70% capacity, I put the computer to sleep and left it plugged in overnight. In the morning, the battery was back to full capacity. So much for that.
For the last week or so, I've been using custom charge levels. The battery does not start charging until it is below 70% and stops charging at 80%. This has worked well and I'm sticking with it.
On the up side, hovering the mouse over the battery gauge on the taskbar produces a helpful pop-up that displays the custom settings.
On the down side, the software refuses to display the estimated run time in hours and minutes despite being configured to do so.
Maybe that's a blessing in disguise. Back when it did report the run time, this too was buggy. As you can see below, the run time was reported as 3 hours and 4 minutes in one place and 3 hours and 23 minutes in another place.
Being a blogger rather than a lab, I can only report on the hardware that I have access to. Anyone with a laptop computer from another manufacturer is welcome to comment below on how, or if, their machine deals with this.
Update June 8, 2012: I gave this scheme a more thorough test on an older ThinkPad, one running Windows XP and ThinkVantage Power Manager version 1.90. How old was it? So old, that the original spinning platter hard drive had been replaced with an SSD and the original battery had also been replaced.
By default, the machine was always charging the battery up to 100%. I modified this to, again, max out at 80% and verified that it worked with Windows running. Then, I drained the battery below my new customized minimum charge percent, turned off the machine, and left it plugged in overnight. I am happy to report that even without Windows running, the battery still did not charge past the 80% limit.
In my previous tests, I had unplugged the laptop overnight, something that I always do to protect the machine from potential electrical surges. That's just good Defensive Computing.