High School Project: Solar Power to Fix Dead Car Batteries

What a well written and articulate message from you fellows. It is rare we such level of communication from HS students. Well done...

A "well written" from me too.

It is nice that you know about capital letters, spaces and periods. So many kids don't have any idea that they have these keys on their keyboard.

Suggest that a solar panel in a frame is only for the prototype and cementing cells onto the car roof as an improvement that would be used in production. This would reduce wind drag, simplify the mechanical design and greatly decrease the danger of a panel flying off and causing an accident a crash.

Get a data sheet on a solar panel and look at the voltage and current characteristics in bright sun. Then get a data sheet on a battery and look at the bulk and float charge characteristics of the battery. You might be ok but you might need charger electronics between the battery and the solar panel.

reinventing the wheel......

Great, so someone has already done the feasibility and prototyping. Like everything done the first time, it will be educational to do it for themselves.

I think in 24 hours they've already received more than the price of admission.

These kids will do it for themselves, I think.

We've given them some help, but they will still have to present a viable project to their sponsor/teacher/ whoever.

That fact that they came here and made a strong presentation to this group speaks volumes about their character and ability.

My nephew's son was on a winning robotics team recently. They did the all work themselves.

I'll give these guys an A.

I'd like to see the end result, please.

Your first problem is to determine what accessories you want to power.

Headlight take lots, radios not so much. Feeding the output of your panel directly into the battery is the way to go.

So, how big does your panel need to be? Cost, attachment, size, wind resistance, rain, bird poop, dirt will diminish your output.

Research solar panels and their output.

You need a project plan.

Good luck.

Great idea for a project, and good preliminary questions. If you are not yet familiar with diodes, voltage regulators, and charge controllers, Google those terms and you will get lots of info. I think if you set this up right, you won't need a secondary battery.

Welcome to CR4!

a must

GA Tornado nice input.

I have two vehicles that sometimes sit for long periods and wrestled with the problem of my batteries going dead for some time....I found a solution with 20 watt solar panels that sit on the dash board and plug right in to the cigarette lighter socket, with a battery tender wired inline to limit overcharge, this has worked well so far...It will charge a battery from unable to turn the engine over to ability to start in just a few sunny days...sure beats hauling the battery out to have it charged....I did have the diode pack in the alternator go bad on one vehicle that sits the most, it's still not clear if the charging method caused the failure or it just went bad....since then I have disconnected that battery and have it wired to the panel direct, with the battery tender of course....The alternator was not cheap and I'm a little gun shy of the setup until I get the time to test it or find out one way or the other what happened....If you can research this problem it might be of commercial value....Good Luck what ever you decide...

Sort of like this....

http://www.amazon.com/Competition-Solar-47701-Amorphous-Controller/dp/B00A180IBC

I had the same basic set-up to charge the two batteries on my last boat. It worked well, in Arizona.

Good idea and well known and easily available - finished! Its even quite cheap.

Some cars need the cigarette lighter socket rewiring to permanently be connected to the battery, (as those units sometimes need). At least some in Europe do.....or take the ones with the battery clips.

An extra diode and a switch can be added to the cigarette lighter socket to allow usage as a charging socket when normally disconnected as per car manufacturer.

What many forget, is that generally speaking, allowing a car (I do mean CAR!) lead acid battery, type of battery to discharge below around 12.6 volts for long periods, is already damaging the battery....

A leisure battery will handle it far better, but generally will need to be much "larger" to handle the cranking amps needed.... hefty price difference usually not to be ignored either!!

Also, as I have mentioned several times before on CR4, possible overcharging for long periods is also not good for an average car battery either.... so some form of charge control is a good idea.

Also, they should not go for a "full" charge either. The Guys should go for holding the battery between 12.6 to a max of around 13.4 volts for long periods.....that way the battery will have its best life span and it will still start the engine well.

All of this is intended to apply to a 12 volt nominal car battery, with a normal lead acid construction.

Well constructed question.

My feeling is that if you want to cover a worst-case scenario of, say, headlights left on, this will totally drain the battery (just my feeling - haven't done any sums - but think you'd need a BIG solar panel and a LOT of insolation to match that load) - so you'd be better to have the solar stuff charge a secondary battery.

Do the sums.

Good luck.

A charge controller is a must, even the small 10 watt panels will overcharge and destroy a battery. Typical discharge rates are in the 50 ma range for the radio and computer. In a former life I lived on LI in the summer and USVI in the winter, on more than one occasion I neglected to disconnect the battery, both cars 96 Sebring and Wrangler started with no problem. That being said, if the lights are left on, the battery is toast. Once a lead acid battery is discharged to below 10 volts and left discharged it will never recover. Radios are not a problem, most folks remove their keys, though I too have left them over the visor so I wouldn't lose them. Visor lights, and dome lights are the likely culprits. Defective brake pedals and hood and truck lights are also suspect.

That being said, let's pretend.... Go for the visor lites, S.O. invariably leaves them on. (S.O.= Significant Other) Design your circuit(s) around this. There is no way to account for all contingencies, go for the most likely. If you build the charge controller, go to battery university, they will tell you every thing you ever wanted to know about charging batteries. As you live in WA, insolation tables will be required. They will be quite interesting.

After you have done this for a visor lamp(s) run the numbers required for brake lights or headlights, the numbers will astound you.

After you complete this project, you will become proponents of coal fired power plants.

Best, give us progress reports.

Very good post. Thanks!

Couple of considerations:

• if car is parked for prolonged period of time but under cover - the placement of solar panel is to be determined. Maybe make it optional on the car or the roof of the garage.
• If there is an electric fault the solar panel might still not solve the problem of any current leakage
• 4WD might have dual batterie systems and I am sure there is a solar powered option readily available
• space to install the second batterie has to be considered

Not much time now. Good luck and report back what you came up with.

Very articulate presentation. Much better than most of the members, including myself, normally do.

Boats, especially sailboats, use a system almost identical to what you are attempting. If this is to be mounted on a car, there are flexible solar panels that will follow the contour of the roof lines and not very expensive http://www.westmarine.com/flexible-solar-panels

Their output is controlled by a solar charge controller, very inexpensive, http://www.westmarine.com/buy/kisae-technology--sc1210ld-solar-charge-controller--14159990 Which distributes the solar charge to a battery (lead-acid) and the load.

By using a battery "splitter/isolator" you can charge the solar panel battery, both batteries, or have the panels and the panel battery power the load. This unit prevents the main battery from being discharged by the solar panel load. This can be either bought or an inexpensive one made from some diodes. http://www.westmarine.com/buy/mastervolt--battery-mate-ig-1602-2-battery-isolator--13009840

One problem you may be confronted with is that when lead-acid batteries are discharged below a certain point they can not be "renewed". For the solar panel battery use a deep cycle battery. It will handle this problem better.

Larger power boats use a system almost identical to what you are investigating. They have batteries for starting the engines and an accessory battery. The starter batteries can charge the accessory battery only if they are at a higher level than the accessory battery. Likewise the accessory battery will not supply power to the starter batteries in order to keep it from becoming discharged from the engine load. One provision sometimes provided is a manual switch to allow the accessory battery to start the engines one at a time. This is in case the engine batteries became discharged for some reason.

Good Luck with the project. Read up on boat solar charging systems. You will be able to find information applicable to your needs. I use an identical system to maintain the battery charge on my accessory battery, mostly electronics, while under sail in one of my sailboats.

Good Luck, Old Salt

I realize that a "dead' battery is a common term for a "flat" or more correctly "discharged" battery but a dead battery is one that cannot be charged. When you do some more research you will find some terms that will be unfamiliar to you. Do ask what is exactly meant by each term and find and use the correct term in your submission.

This is a worthy project and I suggest you Google 'smart charger' to get an idea of the sort of thing you will need to emulate. A dumb charger can overcharge and cook a battery rendering it dead, real dead that is.

Jim

You might want to build a Bedini SG and use the solar panel as the input "battery". The Bendini is a field collapse amplifier that produces a very short high voltage pulse to the battery that will charge it (and recondition it) without overcharge or heating. The circuit works much like a Joule thief circuit except that the motor portion provides a steady pulse from the inertia of the wheel rather than resonance in the coil-transistor circuit like a Joule thief.

Forget that Mythbusters and MIT couldn't make one work. It's simple and thousands of people including School Girls have made them! Hence the name Bedini SG. You can find lots of examples on Youtube and Google.

I want to repeat the congratulations on using correct English grammar and punctuation. I'm really offended by the lack thereof exhibited by so many...

In case you should decide that your project is, as some have suggested here, reinventing the wheel, I have a suggestion. I've often wondered why the following isn't standard on cars. First, investigate possible safety and legal issues! Devise a system that will use a timer and sensors to turn off the headlights whenever they have been left on for XX minutes with the engine not running. This system might need to turn ON the emergency flashers when it turns the headlights OFF. The emergency flashers use considerably less current/energy than the headlights.

Recently, a friend used my car and turned the headlights to the 'ON' position. We always leave them in 'AUTO', where they turn off automatically after a minute or so to light the way into the house, so thought nothing of it when we got home and the headlights were still on. Of course by morning the battery was fully discharged.

This suggested project could have prevented the discharged battery, whereas a solar cell system would not, since it was night.

Good luck!

Go to a site like Arizona Wind and Solar, and look at their Marine and RV charging packages. Call them, or a number of other companies in the same business, and give them your requirements, loads, etc, and they will design a package for you. Where to put the panels is a concern, and will it be for stationary storage, and using the alternator while driving? Those pesky questions...

To the young gents... may I suggest that you forget the fact that this technology is already present in the market place in many different offerings from various manufacturers and vendors.

The intent of this exercise is not to produce a viable product offering so much as to allow you to discover the "process" involved in designing and developing such a product.

Stick with you original idea and learn all the process steps needed to design and develop such a product. The many offerings in the market place offer you a strong sanity check on the work product of the exercise.

What are some of the steps you envision as being needed to get to the desired end state?

The responses you have garnered so far is one such "part" of this process. When you ask engineers such questions, they often focus almost exclusively on the engineering issues and do not look outside of their field of interest. This is a reality that many people who are involved in a product development process must understand and learn that they must weigh all answers against the business objectives.