On top of what has been said, some chargers simply refuse to recharge when the battery is not low enough. Look at laptops, if you don't USE the battery the thing will stop recharging period. Some of them you have to take the battery out and unplug them to get them to charge again if you do not use the battery.

If the circuitry reads the battery as charged "enough" it may well refuse to charge. It depends on the make and model and type of battery.

Some of them you cannot just "top off" like an old car battery in a 1967 Chevy. They actually require cycling to work properly. So even if it causes you an inconvenience by dying a bit son, the point of the circuitry is to preserve the battery.

The technology is much better than it used to be but is still not perfect, especially when you require amp/hours out of a battery thinner than your credit card. Also, overcharging low quality batteries has been know to cause them to explode.

So when something like this happens, disconnect everythng, and if you cannot take the battery out, make sure to run it down. Watch ten movies on it or whatever, unplugged. Run it down to like 40 % and I bet it will charge. If not, there might be something wrong with it. (or the charger of course)