# Hybrid Power System Design for Multifunctional Mini-Loader Vehicles
## 3 Results
### Hybrid Power System and Hydraulic Pump System Tests  
The tests of the hybrid power system include testing the engine, the hybrid power, and the battery mode. The steps involved in testing the engine mode is shown in Figure 7. The test first confirms that the engine fuel valve and the spark plug coil switch have been turned on. The controller is switched on, and the rotational direction of the motor is verified. The motor speed knob is turned; as the motor rotates, the engine ignites and starts successfully. If the engine does not start, a dipstick is used to check whether the fuel quantity is sufficient. After the engine starts, the motor is shut down, and the motor is converted to a generator to charge the battery. For battery charging, this study limits the maximum charging current to 5 amps and sets the charging mode to be turned on when the state-of-charge (SOC) is less than 60%. The measured charging current is shown in Figure 8. When the motor rotates, it consumes about 10 to 12 amps of current. When the motor is turned off, it becomes a generator, and the charging current is stable at 5 amps. At 30 s, the charging current suddenly drops. The reason is  
Figure 5: 3D diagram of the hydraulic system and the tool modules.  
Figure 6: Hybrid power multifunctional mini-loader vehicle.  
that the clutch is being connected and the low gear is engaged to move forward, which slows down the rotational speed slightly. By engaging the throttle, the current can be maintained at 5 amps.  
Figure 8: Charging the battery module by the motor.  
Figure 7: Testing the engine mode.  
The hybrid power mode mainly controls the motor and the engine at the same rotational speed to increase torque. The testing procedure for the hybrid power mode is almost the same as that for the engine mode. The only difference is that the system controls the motor and the engine at the same rotational speed after the engine starts; if there is a speed difference, the power output becomes worse. The testing procedure for the motor power mode is the same as that for the engine and the hybrid power mode. It should be noted that when the residual capacity of the battery is lower than 60% during the motor mode, the system automatically switches to the engine mode to assist in battery charging. When the residual capacity is higher than 90%, the system switches back to the motor mode. The residual capacity of the battery and the usable time are calculated as in Equation (5):  
\[\text{SOC}=\frac{battery\ charge}{charge\ after\ charging\ is\ completed}. \tag{5}\]  
In Equation (5), SOC is 60%, the charge is 12 Ah after charging is completed, and the average motor current is 10 A. The experimental record is shown in Figure 9. Therefore, it can be calculated that the battery has been used for 4.8 Ah and 28.8 min. This demonstrates that when the battery is used from 100% to 60%, the motor can run continuously for approximately 30 min. For the battery charging test, it takes about 40 min to charge to a residual capacity of 90% after switching to the engine mode.  
The electric hydraulic pump operates smoothly after repeated experiments. The average time from the loading of the cargo to the clearing of the cargo into the cargo bed is 10 s.