# Completely solar powered engine -- is my design good?

#### caters

The engine of a solar car I am designing(for my fictional stories but I would like a scientific point of view on this) is literally a DC circuit combined with mechanical force.

First of all, there is a rechargeable battery. I would say it is about 24V fully charged. There are 2 wires coming off the battery(Positive or hot and Negative or neutral respectively)

Connected very closely to the battery are the positive and negative leads of a voltmeter. This voltmeter is used as a battery gauge. I am not sure at all where to put an ammeter to prove the battery is dead or not. I mean the circuit is complicated as is(multimeter wouldn't work so I do need a separate voltmeter and ammeter for this circuit). There are 2 separate motors, each with their own positive and negative wires. These motors is where mechanical force comes into play. Each motor has to have the same voltage and current if the car is to go straight and the only time it should be different for each motor is when turning the car while it is running(Voltage should be lower in the motor that is in the same direction as the turn(so lower right motor voltage, right turn, lower left motor voltage, left turn). Also each motor is connected mechanically to the wheels in order to make the car move. But the only fuel here is the battery and this battery is a solar battery.

The radio, speedometer, and distance meter(don't remember what it is called) also have their own positive and negative wires. All the negative wires are connected to the negative terminal of the battery and all the positive wires are connected to the positive terminal of the battery.

The voltmeter has to be turned off separately from everything else. An ammeter would also.

But anyway, I am not sure how I could without an integrated circuit(basically a mini computer acting as a resistor in this case) control the voltage in such a way that less current is sent to either the left or right motor(depending on turn direction) and thus there is a lower voltage across that motor when the car is turning. I mean any old resistor won't do. I am not sure if variable resistors will work or not to drop the current and the voltage in 1 and only 1 motor during a turn.

I was wondering if you could help me work this out.

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#### Algr

Wow,

You are using a lot of terms incorrectly, and then describing details without the fundamentals of how anything works. What is "Solar" about this battery? Where does the energy actually come from? A traditional car can't be steered by varying the speeds of the wheels, but you don't describe any wheel configuration.

If I were you I'd just write about what you know and don't go into details about fictional technology.

#### caters

The solar part of this battery is that it is charged with solar power. And why would varying the voltage not work, especially lowering the voltage more on 1 side. I mean the higher the voltage, the higher the speed. The energy for the whole circuit comes from the battery itself so if the voltage of the battery is too low, it won't work and has to be charged(this is where the solar comes into play is charging the battery).

I mean if the right side is going faster than the left side, you will get a left turn(or a counterclockwise rotation). For that to happen in a circuit, the voltage has to be lowered on the left side and the lower the voltage, the lower the current. Voltage is needed for there to be any current so if voltage is 0, current is 0.

Similar logic applies to a right turn.

#### Randy Beikmann

Gold Member
Steering by applying more driving power to one side of the vehicle is OK on slower vehicles like tanks or bulldozers, but would be very unstable and unreliable in a car. And you'd never be able to pull into a parking spot without skidding the tires a lot.

I'm with Algr in trying to interpret the rest of what you said. It's difficult to follow what you're trying to do, and why.

#### Algr

Agreed. Also, you haven't described anything about the car that makes it "solar". Batteries don't care where the electricity comes from. Are there solar cells on the roof or something?

What are the two unpowered wheels doing when the car is making a turn? Do they get dragged sideways across the pavement? Do they turn freely like the wheels on a shopping cart?

Homework Helper
Gold Member

#### CWatters

Homework Helper
Gold Member
Since this is fiction and you don't plan to build one I would....

The radio, speedometer, and distance meter(don't remember what it is called) also have their own positive and negative wires. All the negative wires are connected to the negative terminal of the battery and all the positive wires are connected to the positive terminal of the battery.
Change that so you have a "control panel" between the battery and radio/speedometer/trip meter. This allows you to switch off the radio and reset the trip meter etc.

But anyway, I am not sure how I could without an integrated circuit(basically a mini computer acting as a resistor in this case) control the voltage in such a way that less current is sent to either the left or right motor(depending on turn direction) and thus there is a lower voltage across that motor when the car is turning.
Insert a "motor and battery management computer (MBMC)" between the battery and motors. The solar panels will also connect to the MBMC. The MBMC will control the speed of both motors in response to the steering and throttle. It would also magically turn the motors into generators and recharge the battery when you brake (regenerative braking). It will also maximise the efficiency of the solar panels by drawing power from them at the best "operating point". It would also control charging of the battery and send signals to the battery gauge to indicate how much energy is left in the battery.

First rule of good writing is to write about something you know about.

"Completely solar powered engine -- is my design good?"

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