Optimum battery reconnect for a field controlled electric vehicle

A drive system for an electric vehicle comprising:

• a direct current drive motor having an armature winding;
• a separately excited field winding disposed within said direct current drive motor;
• a plurality of electric batteries connectable in a high voltage connection and a low voltage connection for supplying power to the armature of said direct current drive motor;
• a throttle connected to control current flow through said separably excited field thereby controlling the speed of said direct current drive motor;
• first switching means for changing the connection of said plurality of batteries from a low voltage connection to a high voltage connection at some selected speed determined as a function of battery output voltage;
• and
• said first switching means switches from said low voltage connection to said high voltage connection at a vehicle speed as determined from the equation ##EQU13## where:
• n is the vehicle speed;
• Vb is the voltage of one of said plurality of batteries;
• Ra is the resistance of the armature of said direct current drive motor;
• Rb is the resistance of one of said plurality of batteries;
• Ia demand is a signal proportional to the setting of said throttle;
• and
• p and k are constants selected to give the desired operation.

A drive system for an electric vehicle comprising:

• a direct current drive motor having an armature winding;
• a separately excited field winding disposed within said direct current drive motor;
• a plurality of electric batteries connectable in a high voltage connection and a low voltage connection for supplying power to the armature of said direct current drive motor;
• a throttle connected to control current flow through said separably excited field thereby controlling the speed of said direct current drive motor;
• first switching means for changing the connection of said plurality of batteries from a low voltage connection to a high voltage connection at some selected speed determined as a function of battery output voltage;
• and,
• a second switching means for changing the connection of said plurality of batteries from a high voltage connection to a low voltage connection when the electric vehicle is decelerating and the field excitation of said separately excited field is at least equal to 100% field excitation.

An electric vehicle comprising:

• a direct current drive motor;
• a separably excited field winding disposed within said direct current drive motor;
• a plurality of electric batteries connectable in a high voltage connection and a low voltage connection for supplying power to said electric vehicle;
• first switching means for changing the connection of said plurality of batteries from the low voltage connection to the high voltage connection;
• an optimum operation controller means for causing said switching means to switch from the low voltage connection to the high voltage connection, during acceleration of said electric vehicle, at the minimum speed for which the field current in the high voltage connection required to keep armature current below a predetermined value remains below 100% of rated field current;
• and,
• a second switching means for changing the connection of said plurality of batteries from a high voltage connection to a low voltage connection when the electric vehicle is decelerating and the field excitation of said separately excited field is at least equal to 100% field excitation.