I believe 20-80% is the ideal range for keeping a lithium battery.

 

Plus a full dscharge/ recharge cycle once in a few months to recalibrate it.

 

There's nothing wrong with charging to 100% though and leaving it on the charger AFAIK

The 80% would be if you were to keep it in storage for a long period of time(weeks/months), but I cant remember the technical reason at the moment.

 

Since my childhood was spent on NiCad batteries... I obsessively do full discharges. Lithium is supposed to be very forgiving though. I would just google lithium batteries for your answers...

 

I have years of working practical experience with rechargeables of all types, and recalibration is rarely needed since Li-Ion/Polymer batteries have a microchip that monitors voltage, current, charge state, number of charges, etc. These are called "intelligent batteries" due to the integrated chip. Generally a recalibration is not required for at least a year of typical usage, and ONLY if the device does not recognize the state of charge properly.

In other words, if your device and battery appear to work fine, then just use it and forget about the battery.

My only caveat is that Li-Ion batteries should never be fully discharged. For the longest life of these batteries, it's best to top up in the top half of the charge level - 50% and up. Granted, most people use their devices and expect to run it down lower, and occasional discharges to the point of the device powering down is ok. Just remember to NEVER turn on a device that has shut itself off - that's where you risk over-discharging the battery and triggering the safety feature of the microchip. If the voltage/charge state is too low, the microchip will prevent recharging the battery.

So if the device runs the battery down and shuts itself off once in a while, that's fine. Just remember to plug in the device and start charging it BEFORE you turn it back on.

Happy charging!

 

That's correct as the microchip shuts off the charge current and prevents overcharge.

One of the funniest hold-overs from Ni-Cad/Ni-MH days is the "charge for 8 hours before first use". That's totally false as the microchip will cut off the charge once it's fully charged, so leaving it on longer does nothing at all - it will not extend the battery life in any way.

Speaking of this, many people believe that battery life improves after several charge cycles. That's a myth. What happens is the first few charges we naturally "play" with our devices a lot at first to get familiar with them. Once the newness level drops a bit, we don't constantly play with the device and battery life APPEARS to improve as we use the device less.

Actually the recommended charge level for storage is 40%, with normal temperature extremes - don't freeze it and don't overheat it. The reason is that Li-Ion uses a corrosive chemical reaction that is somewhat unstable, and storing at higher levels causes faster deterioration of the membranes in the cell structure. 40% is high enough that it will maintain a charge level long enough to prevent triggering of the safety circuit for up to a year. Li-Ion should never be stored for longer periods. If you intend to store for a long time, it's a good idea to recharge the battery once or twice a year to keep it stable and functional.

 

Ideally you never want to run below about 30%, but we all know that's not practical for a phone or tablet. As I mentioned in my above posts, just try to keep it charged up whenever you can and the battery will last longer.

Once of the great things about Li-Ion is that they work best with partial and top up charges. As long as the battery hits about 50% or more, you can unplug it and use it. Don't be afraid to unplug it when it hasn't reached a full charge. There are many times where you may need to give it a partial charge and run out the door...that's ok as long as you're not silly about it.

 

I was not talking about calibrating the battery, but rather the tablet so it sees the battery's capacity properly.

P.S. And I have a lot of experience with charging batteries too.