The "memory effect" was seen in early NiCd (nickel cadmium) rechargeable batteries. Where, if you recharged them repeatedly, from a partially charged state, they should seem to lose capacity, "remembering" the partially charged level as discharged. The fix was to occasionally "cycle" them, which was to discharge them and then fully recharge them.
NiMH (nickel metal hydride) batteries do not exhibit "memory."
Virtually everything these days uses some form of lithium ion/lithium polymer battery. And these also have no memory effects. And the way they are charged, they cannot be overcharged. They charge via a Constant Current/Constant Voltage cycle. For the intial part of the charge cycle, the charging circuit limits the voltage to give a certain charge current (normally about 1x the battery capacity, so a 1000 mAH batter, would be charged at 1000 mA). When the voltage gets to the max voltage for the battery, the charging circuit switches to constant voltage, and just holds that voltage and the charge current ramps down as the battery fully charges. For long live, many devices stop charging at the changeover point (which is about 90% of a FULL charge). This gives MANY more charge cycles before the battery dies.
And with lithium based batteries, you will KNOW if the battery gets overcharged. The battery will, as the manufacturers state, "Vent with flame." Or they basically explode in a fire ball.
Slightly overcharged, they get VERY hot (think the Dell and Sony laptop recalls).
I have noticed that my 650 charges strangely. I use an iGO system (www.igo.com
). With that, if I charge until the red light goes out, the 650 shows 4 bars, full charge, but it drops to 3 bars more quickly. If I charge via USB, it takes longer to drop the first bar.
And lastly, I did notice that the last computer I built, using a Gigabyte motherboard, had a utility to leave the USB ports powered, when the computer is sleeping or off.