A battery charger with an improved battery retention system is provided. The battery charger includes at least one pocket having a bottom and sidewalls. A pair of battery engagement rails, or coupling rails, extends outward into the pocket at an angle that is non-orthogonal with the sidewalls. These non-orthogonal rails, which may include embedded electrical contacts, mate with non-orthogonal female slots in a battery pack housing. The non-orthogonal angle prevents lateral forces applied to the battery from causing intermittent electrical connections between the battery pack and the charger. Additionally, the non-orthogonal angle of the rails allows batteries of various sizes to be inserted into the pocket while ensuring a consistent and reliable electrical connection.

The object of the invention is a method for charging a rechargeable battery having non-liquid electrolyte, which battery has an internal resonance frequency. The charging process contains at least one charging interval performed with current pulses, the frequency of said current pulses is essentially identical with the internal resonance frequency of the battery to be charged. Following the charging interval consists of periodic current pulses optionally a second relaxation interval is inserted, in which no charging current is applied to the rechargeable battery, within which optionally a second discharging interval is applied. After the second relaxation interval the charging is performed in an interval consists of a continuous charging current, whereafter an optional first relaxation interval is inserted, within which optionally a second discharging interval is applied. This sequence of the above steps can be varied and applied repeatedly until the full charge of the battery is attained.

An electrical combination, a method and a power tool. An electrical combination may includes an electrical component including a component housing, and an electrical circuit supported by the component housing, a first terminal assembly at least electrically connectable to the electrical circuit, a second terminal assembly at least electrically connectable to the electrical circuit, a first battery including a first battery terminal assembly electrically connectable to the first terminal assembly to electrically connect the first battery to the electrical circuit such that power is transferable between the first battery and the electrical circuit, and a second battery including a second battery terminal assembly electrically connectable to the second terminal assembly to electrically connect the second battery to the electrical circuit such that power is transferable between the second battery and the electrical circuit. The second battery may be different than the first battery. At least one of the first battery terminal assembly is not electrically connectable to the second terminal assembly and the second battery terminal assembly is not electrically connectable to the first terminal assembly.

An electrical combination including a power tool manufactured by a first power tool company, the power tool including a tool housing and an electric motor supported by the tool housing and operable to drive a tool element, a battery manufactured by a second power tool company, and an adapter separate from and connectable between the battery and the tool housing to support the battery on the tool housing.

The invention provides an electrical combination including a power tool having a housing supporting a motor, which is operable to drive a tool element. The electrical combination also includes a battery and an adapter supportable on the housing of the power tool and electrically connectable to the power tool and the battery such that the adapter transfers electrical power between the battery and the motor. The adapter has a locking arrangement engageable with the battery for preventing the adapter from being removed from the power tool housing while the battery is connected to the adapter.