As far as I know charging lithium batteries takes place in 3 stages, namely:
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1. The main phase in which the battery is charged by a current amounting to ~ 0,4...1 from its nominal capacity. During the primary stage, the battery gains about 70-80% of their working capacity.
By the way, the duration of the basic stage of the charge indicated in the documentation on the phone but after the phone reports the completion of charging;
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2. Finishing the stage at which the battery gets up to its full capacity. Formally, this step is optional, but it is thanks to him, the battery may reach 20-30% of its capacity proportionately increases the battery life of the device. The magnitude of the charging current at this stage is gradually reduced, and the completion of the charging is the time when the charging current will be quite small magnitude from their initial values.
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3. Phase compensation charge. If after the completion of battery charge, the phone was not disconnected from the charger, with some frequency, is charging a small current to compensate the discharge.
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\rIt means much harm, from holding the phone on charge there.
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By the way, despite the fact that lithium batteries the memory effect is almost absent, for maximum battery life it is recommended to periodically perform a full cycle charge-discharge – fully discharge (by disabling the phone with the message "Battery is low") and fully charge the battery.