Debian Hardware :: Lower Laptop Battery Charging State To Prolong Battery Life

getting back to our laptop, the stability window is ~3.2V. Meaning that when you operate the battery above this the electrolyte is oxidized on the positive electrode and reduced on the negative electrode. Remember that we only want to oxidize and reduce the active materials and don't want to do anything else. All these reactions other than the ones we want are called side reactions� and these are really bad for the battery. The nominal voltage of a laptop battery is 3.7 V which means that something bad wants to happen as we use the battery.So long story short, stuff (e.g., passive layers and poor kinetics of reactions) happens and things are not as bad as they seem and you can increase the voltage up to 4.2V without bad things really happening. All chargers for Li-ion cells today cut the battery off when it reaches 4.2V. What you have to realize is that at 4.2V, these side reactions are present in finite amounts and start to chemically kill the battery, but its not that dramatic.

Operating to 4.1V makes things better and extends the life, 4.0 V is even better and so on. So why don't battery manufacturers cut the voltage off at, say, 4 V to get better battery life? Because every time you cut this voltage down you decrease the capacity of the battery and its run time. The 4.2V cutoff is a compromise between good run time and decent (read "not pathetic) life.On the other hand, if you charge the battery and then pull the plug (so to speak), the battery discharges some, the voltage drops, and these reactions become less of a problem and your battery life goes up. So the best things you can do is to charge the laptop (or cell phone, camera etc.) and once its charged, pull the plug. Your battery will thank you for it.As a matter of fact, if you own a Lenovo Thinkpad, you can actually change the state of charge to which you charge the battery using the Battery Maintenance� utility. You can change this from charging to 100% state (where the voltage is 4.2V) to 90% so that your voltage is less. You lose some energy is doing that, but atleast you can change it to 100% when you need battery power and put it back down to 90% when you can plug in. I wish my Mac has the same feature.

I typically use the battery for a while (say 1/2 hour to 1 hour), then plug it in and wait to fully charge it, then I pull the plug and use it again for 1/2 hour to 1h and then I repeat this. Takes some getting used to and I forget to do this, but I try.