How Long Can the Mini Car Run?
Exploring the Power and Efficiency of a Solar-Powered Super-Speed Mini Car
10/8/20242 min read


Building a super-speed mini car with solar charging capabilities is not only exciting but also eco-friendly. In this project, we'll break down the components, power consumption, and how long the mini car can run using a 3.7V 400mAh lithium battery and a 5V 2W solar panel for charging.
Battery and Expected Run Time
The battery has a capacity of 400mAh (3.7V). Based on a typical estimation, the mini car's expected run time is approximately 8 hours when the power consumption is around 50mA. However, we’ll take a closer look at the exact power consumption to give a more accurate prediction.
Components and Power Consumption Breakdown
N20 Motor (3.0V-12V)
The motor's power consumption depends on the voltage supplied. We’ll consider two configurations using step-up boost converters to either 5V or 12V:
Boost Option 1 (3.7V to 5V):
At 6V, the motor consumes 20mA.
Boost Option 2 (3.7V to 12V):
At 12V, the motor consumes 30mA.
With 80% efficiency:
Motor power: 12V × 0.03A = 0.36W.
Adjusted for efficiency: 0.45W.
LED Lights
We’ll also add two LED bulbs, each consuming 3V and 20mA.
Power consumption for two LEDs: 3V × 0.02A × 2 = 0.12W.
Total Power Consumption
Boost Option 1 (5V):
Motor + LEDs = 0.15W + 0.12W = 0.27W.Boost Option 2 (12V):
Motor + LEDs = 0.45W + 0.12W = 0.57W.
How Long Can the Mini Car Run?
Given the battery capacity of 1.48Wh (3.7V × 400mAh):
Boost Option 1 (5V):
The car can run for 1.48Wh / 0.27W = 5.48 hours.Boost Option 2 (12V):
The car can run for 1.48Wh / 0.57W = 2.6 hours.
Solar Panel Charging
The solar panel you’re using is a 5V 2W panel, capable of delivering up to 400mA in ideal conditions. Assuming 80% charging efficiency, here’s how fast it can recharge the battery:
The panel provides 0.54A to a 3.7V battery.
Charging time: 400mAh ÷ 0.54A = 0.74 hours (approximately 44 minutes) under ideal sunlight.
Conclusion
Using the solar panel, you can recharge the mini car's battery in just under an hour during peak sunlight. Depending on the chosen motor setup, the mini car can run for anywhere from 2.6 to 5.48 hours before needing a recharge.
This project demonstrates how solar power can be efficiently integrated into a high-speed mini car, combining speed with sustainability. With proper sunlight, you can keep the fun going almost indefinitely!
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