Batteries in solar-powered cars

[huzzi.123]

How can the batteries used in solar-powered cars be different from the normal ones used in combustion cars?

Also, do both of them involve electrolysis to convert chemical to electrical energy?

 

[mfb]

Batteries in solar-powered cars have to power the car, batteries in conventional cars do not. All other differences follow from that important point, and you can look up the details (which type is used and so on) in the internet.

 

[huzzi.123]

Okay. In addition to the batteries, motors come in handy in running a vehicle by drawing the electrical energy from batteries and converting them into mechanical energy, right?

 

[mfb]

A car without a motor won't work...
But the power source for the motor depends on the type of car.

 

[huzzi.123]

Yeah but I'm just talking in general.
So I'm writing the general steps below of how a solar car works (briefly):
Solar panel absorb solar energy
PV arrays convert it into electrical energy
Electrical energy is used to charge up the batteries
Energy from battery will be drawn to convert into mechanical energy to make the vehicle run

Correct me if I'm wrong.

 

[mfb]

That is correct.

 

[huzzi.123]

That is correct.

By the way, I'm wondering if OHM's law can be used in any of the processes I stated above?

 

[CWatters]

The rules for solar powered car races may or may not allow onboard batteries to be precharged before the race. This may effect your choice of battery.

 

[huzzi.123]

I'm just considering solar-powered car for my project. And I was confused about the battery it uses. I think deep cycle batteries are used in such cars but I want to assure if they use electrolysis to convert chemical to electrical energy like the normal batteries?

 

[mfb]

By the way, I'm wondering if OHM's law can be used in any of the processes I stated above?

Define "can be used". It can be useful to calculate some things you might be interested in, but we don't know that based on your very general descriptions.

 

[huzzi.123]

Define "can be used". It can be useful to calculate some things you might be interested in, but we don't know that based on your very general descriptions.

Is there any principle that can be used to find the power a solar car can generate?

 

[mfb]

Incoming solar radiation on the cells * efficiency of the solar cells?

 

[huzzi.123]

Which principle defines this formula?

 

[mfb]

The definition of efficiency (and common sense). Please try to find answers to questions on your own first, especially if they are that basic.

 

[berkeman]

Thread is closed for Moderation...

Thread re-opened.

 

[CWatters]

I'm just considering solar-powered car for my project. And I was confused about the battery it uses. I think deep cycle batteries are used in such cars but I want to assure if they use electrolysis to convert chemical to electrical energy like the normal batteries?

Most, or at least the best, solar powered cars have been built for competition use. Lithium rechargeable batteries are typically used as they have better energy density (energy per kg). You can look up how they work.

However i hesitate to suggest you attempt to build your own solar powered car based on a lithium battery. Even Boeing have had safety issues with lithium batteries and the nature of your question suggests that you have little experience with batteries in general?

 

[CWatters]

Is there any principle that can be used to find the power a solar car can generate?

What do you mean by "power" in this context?

Peak horsepower at the wheels?

Min/Max or Average power available from the solar panels?

Both matter if there are hills!

 

[huzzi.123]

Most, or at least the best, solar powered cars have been built for competition use. Lithium rechargeable batteries are typically used as they have better energy density (energy per kg). You can look up how they work.

However i hesitate to suggest you attempt to build your own solar powered car based on a lithium battery. Even Boeing have had safety issues with lithium batteries and the nature of your question suggests that you have little experience with batteries in general?

Yeah thanks for the response. By the way do you think DC/DC converter is necessary in a solar car just to bring a voltage to a required level before charging the batteries?

 

[huzzi.123]

Or in different term, it's called "MAXIMUM POWER POINT TRACKING (MPPT) SOLAR CHARGE CONTROLLERS"

 

[CWatters]

Yeah thanks for the response. By the way do you think DC/DC converter is necessary in a solar car just to bring a voltage to a required level before charging the batteries?

Or in different term, it's called "MAXIMUM POWER POINT TRACKING (MPPT) SOLAR CHARGE CONTROLLERS"

We can't tell if it's "necessary" without knowing what you are trying to achieve. I mean you could build a crude go-kart using a cheap "camping" solar panel designed to charge a 12V lead acid battery without such a box of tricks but don't expect to be driving it on the highway.

If you want to build something more complex using expensive cells and need to wring every last bit of performance out of them then you might need to go looking for sponsorship and a team of people to build you a special custom charge controller to match them to the battery.

If you actually plan to build something I suggest you tell us what you want to achieve and what your $budget is.

Electric cars are difficult enough. Solar powered cars are even harder.

 

[huzzi.123]

I'm not actually building it. I'm given a task to write the proposal and final report of the project so I have to include 2 research questions & 2 corresponding principles involved. One question is how can the solar energy be converted into electrical energy? The principle involved in photo electric effect.

I did some research and came across a diagram which shows the use of DC/DC converter which is used to stabilize the voltage before charging up the batteries. But its schematic diagram doesn't really involve any principle. If I could think of it as a transformer then I could use mutual induction as a principle but..

 

[berkeman]

Or in different term, it's called "MAXIMUM POWER POINT TRACKING (MPPT) SOLAR CHARGE CONTROLLERS"

I'm not actually building it. I'm given a task to write the proposal and final report of the project so I have to include 2 research questions & 2 corresponding principles involved. One question is how can the solar energy be converted into electrical energy? The principle involved in photo electric effect.

I did some research and came across a diagram which shows the use of DC/DC converter which is used to stabilize the voltage before charging up the batteries. But its schematic diagram doesn't really involve any principle. If I could think of it as a transformer then I could use mutual induction as a principle but..

Yes, using a DC-DC converter to achieve the MPPT is very important for efficiency. Keep researching those terms and show us what you find. That is a very important part of your report.

 

[nsaspook]

I'm just considering solar-powered car for my project. And I was confused about the battery it uses. I think deep cycle batteries are used in such cars but I want to assure if they use electrolysis to convert chemical to electrical energy like the normal batteries?

What type of battery depends on the mode of operation. EV traction batteries have requirements that can be best meet by batteries designed for that type of service. For a solar-powered car Lithium Iron Phosphate cells are the safest to use of the common Lithium-ion battery types.
http://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery

http://www.mpoweruk.com/traction.htm

 

[CWatters]

I'm not actually building it. I'm given a task to write the proposal and final report of the project so I have to include 2 research questions & 2 corresponding principles involved. One question is how can the solar energy be converted into electrical energy? The principle involved in photo electric effect.

Ah ok. In that case I would draw a block diagram showing the following five blocks..

Solar cells
A Charge Controller & Battery Management System
The Battery
A speed controller
A motor/generator

You can explain that the charge controller and BMS is a complicated microcontroller based circuit that matches the performance of the solar cells to the battery and provides other support and safety functions. For example it might provide the following features:

Matching the Voltage of the cells to the battery (DC-DC capability).
Maximising efficiency of the solar panels (by ensuring that the solar cells operate at their Maximum Power Point for the available level of illumination and load).
Managing the battery (Preventing over or under charging, Providing a battery "fuel gauge". Temperature control, overload protection)

If the car has regenerative braking it may also provide support for that. Normally this involves turning the motor into a generator and putting the energy back into the battery via the charger. But there is a lot more to it. For example you can't use regenerative braking if the battery is already full, you have to dump the power somewhere else or use conventional brakes that waste it as heat.

There are several ways to build a DC-DC convertor. The type used in a solar powered car is probably going to be based on some sort of switched mode power supply due to the power levels involved and the need to maximise efficiency. These would use inductors/transformers so it's not unreasonable to refer to mutual induction as a principle of operation.

That should give you some ideas but don't just copy the above into your report. I may have inserted a deliberate mistake :-)

 

[huzzi.123]

Thanks. I wonder if step down transformer can be used in place of DC/DC converter. And the principle it uses is mutual induction.

 

[CWatters]

Many DC-DC converters actually contain a step down (or up) transformer...

They take in DC at one voltage
Convert it to High Frequency AC.
Pass it through a step down (or up) converter
Turn it back into DC at another voltage.

 

[huzzi.123]

I saw so many photos of the DC-DC converters and it looks really different from the transformers like it has diodes, capacitors and inductors. Is there any specific kind of DC-DC convert that functions as a transformer?

 

[berkeman]

I saw so many photos of the DC-DC converters and it looks really different from the transformers like it has diodes, capacitors and inductors. Is there any specific kind of DC-DC convert that functions as a transformer?

Have you read the wikipedia link on DC-DC converters? Do you have a specific question about it?

 

[huzzi.123]

Have you read the wikipedia link on DC-DC converters? Do you have a specific question about it?

Switch mode DC-DC converter and magnetic DC-DC converter. Both of them store their energy in magnetic field and thus the transformer.
Thanks :)

Just to make sure:
So to convert from DC to AC, I'd have to use an inverter to make sure AC goes into the transformer. And an alternating low-voltage value comes out of the transformer has to go through a rectifier for it to be converted to DC and then it goes to batteries to charge them up.

 

[berkeman]

Switch mode DC-DC converter and magnetic DC-DC converter. Both of them store their energy in magnetic field and thus the transformer.
Thanks :)

Just to make sure:
So to convert from DC to AC, I'd have to use an inverter to make sure AC goes into the transformer. And an alternating low-voltage value comes out of the transformer has to go through a rectifier for it to be converted to DC and then it goes to batteries to charge them up.

Sort of. A switch-mode DC-DC converter can either boost the input voltage up to a higher DC voltage (with the AC waveform as an intermediate waveform), or it can convert the input DC to a lower output DC voltage. It all depends on what your voltage source is and what kind of output voltage you need.

And you can even use slightly more complicated DC-DC converters, which can either boost or lower in their transfer function. One version of this is called a SEPIC converter. It is used for example when your source voltage may be coming in either above or below your desired output voltage.