Disconnected Charger Draining Device Battery

With the mains power off, where would the electrons go? There's no complete circuit.

Well, he's saying he wants to leave the unit connected to the battery charger, with the charger turned off.

In my experience, some chargers will drain the battery, some won't. I imagine that the modern designs for Li batteries are sophisticated enough to prevent it, but the only way to be sure is to test your particular unit.

Another factor to consider is "self discharge". Wiki says:

• Self-discharge rate of approximately 5-10% per month, compared to over 30% per month in common nickel metal hydride batteries, approximately 1.25% per month for Low Self-Discharge NiMH batteries and 10% per month in nickel-cadmium batteries.[48] According to one manufacturer, lithium-ion cells (and, accordingly, "dumb" lithium-ion batteries) do not have any self-discharge in the usual meaning of this word.[36] What looks like a self-discharge in these batteries is a permanent loss of capacity (see Disadvantages). On the other hand, "smart" lithium-ion batteries do self-discharge, due to the drain of the built-in voltage monitoring circuit.

I had to go to Sanyo Lithium AA cells in my camera because the common USA ones have so much internal leakage, that they are about as useless as nicads in this area of self-discharge. Sanyo calls theirs, "Enerloop". If I leave my camera off for a week at least I know that my batteries won't self-discharge. So, it is possible to make decent cells, at reasonable cost. I don't know why they don't, but just vote with my dollars. In your charger, it is highly possible that there is leakage through some reversed-biased diode, or active device's junction - however small. You figure that this is ongoing 24-7, and it will take its' toll on discharging the cells.

Many cheaply built (notice I did not say Cheap charger!) chargers will drain the battery, even when switched off/unplugged.

Some chargers don't switch off when the battery is full, though this has improved in recent years, but if you have still got ones like that, there is a really cheap and easy trick to stop major overcharging. It goes like this:-

Buy a cheap 24 hour mechanical timer (big dial, tiny synchronous motor). Rewire it so that the tiny little clock motor only gets its mains power from AFTER the on/off micro-switch (the output socket instead of the input plug for example).

Put a pin in (the programming pins or similar on the perimeter of the clock dial to set the on and off times) for off the time required that you want to run to, I generally use 14 hours/ 14:00 for example....

Set it to midnight, make sure its switched on, plug in the charger and away you go......when it switches off, the motor stops as well and therefore stops it going on and off over further days......

That is a quick and cheap method to allow a one shot timer up to about 23:45 hours....

If anyone did not fully understand it, drop me a line and I will try and I will try and explain it better.....