Charger, adapter and charging system

A charger comprising:

• a connector adapted in use to be connected to a battery;
• an identification unit configured to perform an identification process of judging whether the battery being connected to the connector is a compliant battery allowed to be directly connected to the connector or a non-compliant battery allowed to be indirectly connected to the connector, and output a result of the identification process;
• a main charging unit configured to charge the compliant battery in conformity with a main charging condition appropriate to the compliant battery;
• an auxiliary charging unit configured to charge the non-compliant battery in conformity with an auxiliary charging condition which does not cause a harmful effect on the non-compliant battery;
• a control unit configured to receive the result from the identification unit, and, when the result shows the compliant battery, activate the main charging unit, and, when the result indicates the non-compliant battery, activate the auxiliary charging unit;
• the auxiliary charging condition includes an unspecified battery charging condition for an unspecified battery which is not corresponding to any of plural specified batteries;
• and
• the unspecified battery charging condition indicates a charging current and a charging voltage which are selected such that any unspecified battery does not suffer from a harmful effect.