[General Topics] brecklundin:
No negative impact whatsoever. People are typically under the impression their devices are ALWAYS running off power supplied by the battery. That was often the case a couple decades ago but not for a loooong time now. Modern batteries have no 'smarts' built into them as their ancestors often had. In fact using the old scheme the battery was really a surge protector plus line conditioner, providing sine wave power output. Today the device manages charge state but eliminates that bonus level of protection afforded when batteries always provided the power.

The way things are setup today you simply cannot over charge the battery. Except, as has already been pointed out, when using a power supply that is significantly more powerful than the OEM dongle. If you are stuck using a much more powerful dongle try and limit charging session length to protect against damage from overheating.

Leaving your device connected 24/7/365 will have zero negative impact beyond the fact lithium batteries should not be stored long term (several months or longer) at more than about 60% of capacity. Typically anywhere in the 40-60% is considered safe. Once upon a time devices arrived at around 50%. Today I haven't bought a new device with less than a 95%, heck 99%, charge out of the box in over 20yrs.

What happens if you just leave it connected when fully charged you ask? Well the charging circuitry combined with that module of the firmware (aka ROM for younger folks) sense the charge level, and to a lesser degree incoming current, along with battery health then control the process with little or no overhead to us users. When full AC power that was sent to the battery is typically just shut off. Every device has its own tweaked algorithm for power management so all vary slightly but that's the gist of it.

Companies can actually alter the charge scheme via firmware update. My Asus tf300t is a good example example. There were issues in the charging scheme then a firmware update changed it rather significantly and for the better. When paired with the dock it manages the charge state for two batteries. So rather than simply charging each independently all the time the firmware senses charge capacity, when the main battery hits 70% the battery in the dock is used to charge the main while the incoming power is used on the dock battery once it dips below 95%. That was not always the case, it was originally far less efficient. Asus made a change which will prolong the lifespan of both batteries. It keeps each from dropping too low and of course shuts down charging once it reaches an internal charge of around 90% of true capacity (what we see as 100%). The dock battery will not even start to charge until it drops to 95% or less.

The other main killer or lithium batteries is heat buildup. This why it's better to limit the times when the battery drops under 50%. Lower then that can allow the battery to get hotter than ideal when being recharged.

I keep all my devices on their chargers when not being used and get years more out of them then those of my friends who can't be bothered to care.

Remember the typical in service lifespan for lithium batteries is 2-4yrs no matter what. Treat them well and get the 4yrs worse and get around 2 yrs depending. And when lithium batteries for south it will happen pretty much overnight so after about 18 months it's not a bad idea to grab a new battery then begin a rotation until the old one croaks though most devices are considered 'obsolete' by that point. I tend to use my toys a lot longer.

To summarize go ahead and leave it connected all the time as the internal charging subsystem will protect the battery from not only overcharging but excessive charge cycles as well. The one thing it won't do is guard against heat buildup if charging from a nearly depleted state. In the case of a sub 60% battery I charge in multiple sessions. In the case of my LG Motion that means about 20% increments then off the charger for 10-20min or so to let the battery settle.

Hope I wrote this in a way which makes sense sorry of it seems different from other info the ideas not to argue but pass along what I've learned over the years. And of course your mileage may vary and those are the basics which have served me well since we began using lithium batteries after NiCad then NiMH batteries in the 'before timea' and batteries were the bane of our lives! :cool:

Oh, one final comment, the quoted number of charge cycles is not the number o times you can charge the device is an approximation of the number of zero-to-full cycles though we should never ever do that because of heat buildup and it's cumulative harm due to long active charging periods. I wish the charging subsystem logic had a better hold on temp management but they don't for some reason. :confused:

Likely dictated, not typed, on my LG Motion ICS 4.0 .4 with Tapatalk