This seems like an easy enough answer for one of "our experts" on this forum to check and confirm. (Not only am I not an expert, I do not have any of the necessary equipment.)
I recently purchased a tablet (for the first time), and I tend to keep it connected to a charger when at home, but of course the battery does see plenty of deep-cycling, when I take it on the road. However, currently, it can spend days constantly connected to its charger. So, if this is indeed "bad," I would certainly like to know. (It has an internal battery that is not easily replaced.)
When I look at the battery level while it is on the charger, it reads "100% Charged - Full" even though the tiny battery icon shows that it is charging (or at least, connected to a charger). So, I have assumed (up to now) that in this condition the charger is not doing anything... it is simply connected.
Would someone please take a similar device and see whether or not any current is flowing into their device when in this "100% Charged - Full" state? (I would like to think that there is no current flowing at all. But, I guess it would take an accurate meter to verify that fact.)
I would be happy to contribute the adapters that would likely be required to connect an appropriate meter between the charger and the device...
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PS: I just found this post on another forum:
From my own experience as an Android developer, my phone is ALWAYS plugged in when I am at my computer and it is almost always fully charged while I am using it. I have been an Android developer for about 2 years now. I program just about everyday, which means everyday my phone is plugged into my charger while I am programming. I have an old Droid 3 that I use for testing compatibility for Gingerbread (2.3.3). When I got the phone it needed to recharge every other day. Now, unless I use it constantly, it will survive for just over a day. For a 2 year old battery, that is pretty standard degeneration.
If you think about it, everyone pretty much plugs their phone in at night and it will take about an hour to two hours to charge (if the battery is completely dead). That means that the device is sitting on the charger for about 6 hours fully charged every night (if you sleep 8 hours a night). I don't think that a few hours of it on the charger while you are at work will affect your battery's lifespan enough for you to notice.
If anyone has any logical reason or statistically significant data to support the fact that this is a bad idea, then I will eat my words but from my experience I would say that your battery will not experience any significant lifespan decay from you plugging it in at work.
If you want to know more LifeHacker thinks it's a bad idea, but they give no statistical support for their tables
Over at Android Forum it seems the general consensus is that it doesn't matter.
Here at android.stackexchange it seems like the general consensus is that constant charging doesn't really hurt your battery, but you should do maintenance discharges to keep it healthy.