Electric vehicle

Details Electric vehicle Electric vehicle

1998-09-08

2001-05-15

Wong, Peter S. (Department: 2838)

Electricity: battery or capacitor charging or discharging

One cell or battery charges another

Vehicle battery charging

C320S103000

Reexamination Certificate

active

06232743

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an electric vehicle driven by a secondary battery, more particularly to a charge/discharge control of the secondary battery for the electric vehicle.
Performance and reliability of secondary batteries such as lead acid storage batteries, nickel-metal hydride storage batteries and lithium secondary batteries have been improved in these days. Consequently, there have been also developed many devices driven by the secondary batteries. Especially, in recent years, clean energies are aimed widely and electric vehicles such as electromobiles, motor scooters, forklifts which are driven by the secondary batteries are attracting a great deal of attention.
In such an electric vehicle, a vehicle controller mounted in an object vehicle controls the output of the motor, and also monitors and controls the batteries. Monitoring a remaining capacity, an output voltage, and a cooling state, or the like of the batteries installed in the vehicle, the vehicle controller decides the battery state including the level of degradation thereby to control the output of the motor and charging of the battery based on the obtained battery information. In addition, the vehicle controller issued warnings to the driver if necessary.
In the case of a conventional electric vehicle, the battery is considered to be a mere driving power source. The vehicle controller is thus fixed to a vehicle. Therefore, when the battery is degraded or down, the battery is just replaced. Consequently, each time the battery is replaced with a different specification, the vehicle controller set values must be changed so as to correspond with the new battery.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to solve above-mentioned problems and to provide a low price electric vehicle which is highly compatible with many types of batteries and accordingly highly reliable.
The present invention provides an electric vehicle of the present invention comprises: a driving unit for driving the electric vehicle with an electric power; a vehicle controller for controlling the driving unit; a battery unit for supplying an electric power to the driving unit; and a battery charger for charging the battery unit. The battery unit includes plural secondary batteries and means for monitoring states of the plural secondary batteries and for issuing a signal to the vehicle controller based on the obtained information. The vehicle controller controls the driving unit and the battery charger based on the signal from the battery unit.
The states of the batteries have been monitored by the vehicle controller fixed to the vehicle in the conventional electric vehicle. On the contrary, according to the present invention, the batteries and means for monitoring the batteries are disposed in one unit in the electric vehicle. In other words, information on the batteries is obtained in the very unit in which the batteries are installed and the unit issues control commands to the vehicle controller provided outside the unit. On the basis of such control commands, the vehicle controller controls the driving unit and the battery charger.
Generally, a service life of a battery is shorter than that of a chassis of an electric vehicle. Consequently, the battery must be replaced due to the end of life in many cases while the chassis is still in use. Therefore, when a mileage of the electric vehicle reaches a certain value or when the battery usage period reaches a certain value, the battery is replaced. Further, it is also considered that the battery is replaced with a higher performance one in order to improve the performance of the vehicle. Such battery replacement is made as a whole battery unit replacement.
If commands issued from such a battery unit to the vehicle controller are standardized and the monitoring means is set appropriately to the battery specifications, it is possible to omit troublesome changes of set values for controlling the vehicle even when a new battery with a different specification is employed. It is also possible to control the output of the battery more effectively, so that performance of the battery can be shown fully, assuring a high reliability for the electric vehicle.
An electric vehicle is already provided with a predetermined space for installing a battery unit. Therefore, an increased number of batteries can be installed instead of the originally installed battery if the new battery is more compact in size than the original battery and the new battery unit can be accommodated in the predetermined space. Consequently, the electric vehicle of the present invention will be advantageous in space utility. In addition, the vehicle can cope with improvement in battery performance easily.
In a preferred mode of the present invention, the battery unit is composed as one unit detachable from the electric vehicle. For example, if all elements composing the battery unit are housed in a box-like case detachable from the vehicle, the maintainability for battery replacement will be improved significantly.
In another preferred mode of the present invention, the monitoring means detects output voltage or temperature of the secondary battery.
It is preferable that the battery unit is provided with means for cooling the batteries. The cooling means such as a set of an air-cooling sutructure and a cooling fan, or a set of a water-cooling structure and a water pump is provided independently of the vehicle or the vehicle controller. More preferably, the cooling means functions based on the temperature of the secondary battery detected by the monitoring means. When the temperature of the secondary battery rises due to a long running of the vehicle, the cooling means cools down the batteries in each unit appropriately to the characteristics of those batteries.
While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings.


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