I'm using a Lenovo Y50-70 and Conversation mode is always turned on (plugged-in, not charging mode).

Specifically, my question is: Will it damage the battery (or the laptop) if I leave the power cable plugged in even when the laptop is turned off?

And in a more general way: is it better to unplug an electrical device when I'm not using it?

*My laptop's battery is Lithium-ion polymer 4-cell (54Wh) battery

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    \$\begingroup\$ J. Doe - Hi: (a) You aren't designing something, so your question is not a good "fit" here (this site is specifically for design questions, not for all electronics-related questions). I suspect it would be more "on topic" over at SuperUser. (b) Based on my interpretation of "damage", the answer can vary with different laptops - one of mine has a charging algorithm which prioritises keeping a full charge, at the expense of reduced battery lifetime; another doesn't. So I suggest you should be guided by what that specific manufacturer tells you in the user manuals (or ask in their forums). \$\endgroup\$ – SamGibson Oct 23 '16 at 0:20

Mostly, no, it won't kill the battery.

Because overcharging a lithium-ion battery destroys it and often results in fire, there is an absolute requirement that the charging stop. So, your battery isn't going to be "cooked" by leaving it plugged in.

On the other hand, lithium-ion batteries don't last as long if they are maintained at 100% charge indefinitely. This is also true if the laptop causes them to be warm all the time. This is why some will avoid leaving the device plugged in continuously.

As far as leaving the device plugged in is concerned, the power supply will be running, as well as the charging circuits (although they should ultimately be doing nothing). Whatever they are doing will generate heat. If they are well designed, they will draw very little power, and generate very little heat. This is the sort of thing the Energy Star rating is about, that is, wasting very little power on standby.

A fair test, then, is to feel the power supply (if it's external) and the device, after they've been sitting a few hours, with the device turned off. If they feel cold, they're consuming almost nothing. To the extent that they feel warm, they are wasting that amount of power. Even in the latter case, they are unlikely to be damaged unless they were poorly designed. And if the device is off, everything else (besides the charging circuitry) is oblivious to the applied power.

  • \$\begingroup\$ Thank you, and just to complete the answer - does leaving the device plugged in do any damage to it? I mean, electricity comes from the "wall", so if it is plugged to the "wall", electricity flows inside the cable and... probably "hits" the device itself? \$\endgroup\$ – J. Doe Oct 23 '16 at 12:28
  • \$\begingroup\$ Response added to my answer. \$\endgroup\$ – gbarry Oct 24 '16 at 5:14

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