Originally posted by simico I'm afraid then you have a different idea of overcharging. What you call "slightly overcharged" (e.g. +0.02V) is not overcharged, it's within the tolerances.
Yea, I chuckle when people with close to zero technical knowledge make up ridiculous "facts". We use Li-Ion and Li-Po batteries in the industry, also use Li-Po in my hobby (RC vehicles) - I know them very well. Just because the LED is lit when you place the charged battery in the charger again, it doesn't mean it starts a new charge cycle (it would definitely puff and catch fire within 2 minutes then, you can try it with a general charger set to wrong mode if you want to). A working voltage regulator in the cam can definitely handle a few 1/100th V difference, heck that is exactly its job.
Bottom line: if it's broken / malfunctioning then send it in for repair. Nothing else gonna fix it.
So with my close to zero technical knowledge, let me make up some facts.
A guy charges his laptop in he airport, boards the plane and runs right back off with a smoking laptop from the Li -Ion battery. In this case it was a faulty production run of the Sony batteries but it could have been a faulty charger to achieve the same result. Overcharge a Li ION battery and if the Current Interrupt Device doesn't work, around 500 PSI the membrane bursts. Bad. And it'll happen pretty quick. That's not what's happening here.
What is true is that unlike the battery and charger used with the K10/K20, this system behaves differently. First, it charges much more slowly than the K10/K20, nearly twice as long. The battery capacity is different which mostly explains it, 1620mAh for the K10/K20 and 1860mAh for the K5. Its a different cell design and its a different manufacturer or both. The higher capacity is probably to make people happy by lasting longer.
Second, if the cell design drops voltage more quickly (normal after charging) than the previous design and /or the charger has a slightly different threshold, re-seating the battery back in the charger could result in more charging because its dropped a bit. It isn't something you should do but it worked on my earlier cameras.
Post charge, Li Ion batteries can drop up to 500mv volt per cell in a few hours. Which is why a poster mentioned waiting to use charged batteries. The output of the K-5 Battery is labelled 7.2 volts (3.6 +3.6) . The K-5 Charger output voltage is 8.4 (4.2 + 4.2). Li Ion battery cells are typically charged to 4.2v and post charge drop to 3.6. Half a volt can easily be the difference between a logic state and an indeterminate state.
Put a scope on digital circuitry and you'll see raggedy signals that don't look like ideal ones and zeroes. There are rise and fall times and thresholds and noise and all sorts of analog factors. Toss is some vibration, temperature fluctuations and supply voltage that is momentarily on the hairy edge of spec and voila - intermittent symptoms in your micro pc with lens attached.
Bottom line, if I use the battery and charger and camera as the mfr directs, it works without problem. The design point may be overly aggressive in that it isn't completely user proof. Which is when my mother would say Jaj istenem.