thanks but there is any way to know when the battery is fully charged?
leaving in full option for X hours?
in half then in full?¿
There is no easy answer. It depends on initial level of discharge and battery condition and may vary between 2-15 hours.
Typical Li-ion charging algorithm uses constant voltage charging with variable current limit (when current is higher than the limit, it limits to the constant current). If cell temperature is low, charger uses high current, if temperature is high, charger switches to low current or off. Charger also monitors battery voltage. When charge current at constant voltage decreases below defined limit and voltage does not raise any more, battery is considered as fully charged.
Part of this algorithm is embedded into the charging circuit, the rest (current change depending on temperature control and voltage) is implemented in the kernel. See the datasheet (you can find it on my www pages; link in my signature).