Is It OK To Leave My Laptop Plugged In All the Time?

Reader Mike asks: Is it safe to leave my laptop plugged in for extended periods of time when I am not using it? I am talking 10 or 12 hours at a time. Or should I only plug it in when it needs charging?

There are actually two issues at play in this very common question: It it safe to leave a laptop plugged in all the time, and is it bad for the battery to do so? Let's look at both.

First, regarding safety, there's no evidence that shows that leaving your laptop plugged in will cause any sort of danger to the battery. You're right to worry, considering the battery explosions issue of 2006-07, but many of those laptops weren't plugged in at all when they went up in flames, and there's no evidence that those that were plugged in had been left that way for a long time, or that anything other than bad battery design was responsible for their failure.

The truth is that laptops and laptop batteries are designed with the intent that they be plugged in as often as possible. In fact, most manufacturers suggest leaving them plugged in all the time. The heat you feel from the bottom of a laptop that's been running all day doesn't really have anything to do with whether it's plugged in or not. Laptops get hot due to their internal components and the chemical reaction in the battery. The A/C charge has very little to do with it. So, from a pure safety standpoint: Plugged in is just fine.

The other question concerns your battery's lifespan. Will leaving it plugged in decrease its useful life? The short answer is no, at least not enough that you're likely to notice. Lithium-ion batteries have no "memory effect" like nickel-based batteries, so there's no worry about plugging them back in before they're completely drained. But like all batteries, lithium cells lose capacity over time. The more they are drained and recharged, the more their internal structure warps, and they eventually become unusable. This happens due to heat, and since your battery gets hot even when it isn't discharging, as long as you have it installed in a running computer, it's going to be affected to some extent. Now this effect is really pretty minimal compared to constant charge-discharge cycles, but if you turn off your laptop at night and unplug it, or if you run your laptop plugged in, without a battery installed, that battery will last slightly longer when you do eventually start using it (so long as you keep it properly charged most of the time). However, the extra lifespan you gain is not even remotely worth the extra hassle in doing all this work. Bottom line: Leave your notebook's battery installed, and plug it in as often as you can.

HIV WARNING! New Ways of Spreeding HIV!!!!

A few weeks ago, in a cinema, a person felt something poking from her seat. When she got up to see what it was, she found a needle sticking out of the seat with a note attached saying "You have just been infected by HIV (AIDS)".

The Disease Control Center (in Paris ) reports many similar events in many other cities recently. All tested needles were HIV Positive. The Center also reports that needles have been found in cash dispensers (ATM) at public banking machines. We ask everyone to use extreme caution when faced with this kind of situation. All public chairs/seats should be inspected with vigilance and caution before use. A careful visual inspection should be enough. In addition, they ask that each of you pass this message along to all members of your family and your friends of the potential danger.

Recently, one doctor has narrated a somewhat similar instance that happened to one of his patients at the Praia Cinema in Delhi . A young girl engaged and about to be married in a couple of months, was pricked while the movie was going on. The tag with the needle had the message : "Welcome to the World of HIV family". Though the doctors told her family that it takes about 6 months before the virus grows strong enough to start damaging the system and a healthy victim could survive about 5-6 years, the girl died in 4 months, perhaps more because of the "Shock thought". We all have to be careful at public places, rest God help! Just think about saving a life by forwarding this message. Please, take a few seconds of your time to pass along.

Remember ... to pass this on to everyone you know... Probably your mail can help save a life.