A modern, smart battery charger would be most unsuitable to run a car windshield wiper motor.
However, a simple 12V battery charger of yore, with a charging current of 3.5A or higher, would do. Such chargers would have transformers with 'high impedance' secondaries in order to limit the charging current.
Alternatively, all that would be required to rig up a power supply would be a 12 V transformer and a bridge rectifier of adequate current rating.
A car windshield wiper motor would generally draw less than 3A on load.
One would do well to measure the wiper motor current on load, when powered by a 12 V battery.