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Battery-Powered vehicles require that drivable range be maximized. This requirement is at odds with the need to protect the battery from over charge and over discharge. This is especially true when the electric vehicle operator is not sufficiently knowledgeable about battery operation. Several technologies were examined to prevent excessive discharge during operation of a luggage tractor. None of the existing technologies were found to be appropriate for this application. A new scheme was developed whereby battery terminal voltage is compensated by discharge current. By carefully selecting the control curve relative to the internal resistance of the battery, discharge energy output is maximized while still providing protection against excessive discharge. A device was developed using this new scheme.

Results of the Charger Test Project conducted by Arizona Public Service (APS) indicated the importance of the charger/charge algorithm/battery interface with respect to battery capacity. It also indicated that EVs rapidly charged demonstrated longer cycle life in field testing without reduction in capacity. Additional testing conducted by APS has shown that cycle life of the batteries is strongly related to the charging scheme utilized. Application of results of laboratory charging to the charge scheme utilized in this testing has been hampered by extremely long test periods in field tests designed to cycle batteries to the end of life. Development of a predictive method of cycle life extrapolation based upon microscopic analysis promises to reduce the time required for battery cycle life testing.