Solar power

20mg · 05-09-2008, 01:39 AM

so i recently got and idea i found a wing that comes stock on a r32 for about 100 bucks on ebay and im planning on cutting into it to mount some solar panels so i can be recharging my battery when my cars parked. I know they wont be charging it quickly or anything but i figure y car needs all the power it can get. i tried out one of my solar panels by connecting it to they battery today and everything seemed to work. I was just wondering if anyone else has tried to do anything like this and if so what kind of complications might i run into. should i have a fuse between the solar array and battery? ill try to take some pics tomorrow

blackcobra487 · 05-09-2008, 03:04 AM

I would worry about over charging the battery, that would shorten it's life greatly.

Bugbyte · 05-09-2008, 08:23 AM

What voltage is the solar panel? Unless it is greater than 12 volts, I don't think you'll be charging the battery.

Also, if it is possible for it to generate more than 12 volts, I would worry about overcharging the battery, so you'd probably want to put some kind of battery charger in line with the solar array.

Solar panels generate very little electricity unless you have a large array of very efficient ones. To tell if this will be worth it, you should measure the current draw of the car when it is off using a digital multimeter.

Then, see if the solar panels can output that much current. If so, they might help. If not, they will only slow your battery drain.

20mg · 05-09-2008, 11:23 AM

the panels are 12 volt and there are 4 of them. im thinking even if its just enought to slow down the battery drain it would be helpful. now i gotta figure a way to resolve the over charging situation. thanks guys

Seth_jxl · 05-16-2008, 01:29 AM

If its any help. i have had a 12v solar panel attached to a carolla sitting in my drive way for about 3 months. I hadnt started the car in that time and found that the panel was able to hold charge in the battery. I figure this setup would be handy for my situation, however i found the output was not great enough to charge a battery from flat. I believe you would find that a standard wet cell car battery would no longer function correctly when charged flat by a solar panel. This is due to the time it would take to charge the battery.
When dealing with solar panels, i have found after much research that a deep cycle battery is needed.
It all depends on what you wish to used them for realy.

Disefyl · 05-16-2008, 09:41 AM

I havent used solar in a car before, but I have in my sailboat. They work best when used with a deep cycle battery bank; however, I have seen/used them to maintain a trickle charge on the starting battery. Additionally, a diode needs to be used to prevent the solar panel from draining the battery back to the panel as dissapated heat(Often built into higher end panels). I learned this one the hard way. With regards to over/undercharging a battery, I wouldnt recomend wiring the panel directly to the battery. Instead you need to use a controler to efficiently control the current/voltage sent from the panel to the battery.

scloyd · 05-22-2008, 04:29 AM

I've used the small panel from JC Whitney to maintain charge on cars in storage. For a carputer system I will need a much bigger panel to hold a computer in standby or hybernation for an indefinite time. If the vehicle battery can maintain the computer system over night without going into low voltage shutdown I should be able to pull it off here in Arizona. We have about 360 days a year of sunshine. My panel will need to be able to generate 2x the watts that the carputer will need to be in a ready sleep mode.

Seth_jxl · 05-22-2008, 06:32 AM

sounds do-able. would like to know the panels you use, where you choose to mount them and if you decide to use any extra batterys. in my setup, my m2atx is connected to four 12v SLA 7.5AH batt's in the boot. When running the car a relay allous them to be charged and when off they hold the computer in standby. im getting a 4x4 soon so some off road/camping and owuld like to have some kinda of solar setup to run electronics even for an hour or two without having crank the car over and waste petrol.

clifwlkr · 05-22-2008, 02:26 PM

Well I have had a solar panel on my current vehicle, and the one before. Unfortunately I do not have a pic of it, but let me describe it.

First, I have a 64watt panel. In regular sun, it easily generates 4 amps without raising the panel. I build my own mount using angle irons (the ones with the holes). This mount is directly screwed into the topper on my truck. I can raise and lower the panels by removing two screws (hand tight), and propping it up. That can increase me to 4.5 amps, for a much longer period of time.

The panel goes into a small charge controller that allows me to see the battery voltage, panel amps, and load amps. This charge controller connects to a large trojan golf cart battery. I also connect a wire from the car's power to the solar panel input, meaning I am charging the battery while driving. My battery is almost always topped up.

Further, I buit a relay system that automatically switches the load over to the car when it is running. This means I am not running down the battery when driving.

So hitched into it, I have a large variety of items. I have two ham radios. One is a uhf-hf rig. I also have a regular vhf/uhf rig that I also use for search and rescue. It allows me to leave my radio on without worrying about running the main battery down. Second, I often have a stirling engine cooler (always when camping) that provides me cooling set at 38 drawing only 0.7 amps. It can go down to zero, but I have not had a need for that. Third, I can run a set of speakers plugged into ipod, xm, whatever that I use when I am camping, since they use a lot less power than the car stereo and can be adjusted to point to whatever. I have an inverter that I occasionally use as well. I am just now in the process of putting together. Finally, I have a large screen gps that I run most of the time.

So as far as the cooler and radios, in standard weather, can run indefinitely. This would allow me to stay out in the desert for as long as I wanted.

If you have any questions about solar, feel free to ask. I also have a cabin that has both solar and micro hydroelectric systems. I built these as well.

Jim

Beehphy · 06-02-2008, 04:39 PM

The only reason to put a solar panel to your car is to power things without the engine running. I hope your not trying to charge a battery that keeps going dead?

Each car has a alternator designed to keep the battery topped up while the engine is running. If your battery is going dead, you need an alternator cause its broken, or a battery cause it can't hold a charge.

Are you are adding the solar panels to run your car computer indefinately without draining the battery?

To do that is going to require a big (for a car) array.
I'm going to do a swag (scientific wild *** guess) just for fun;

The computer and screen power requirement - 70 watts (ball park)
The charge regulator is 85% efficient - 70 * 1.15 = 80.5 watts
The computer runs 24hrs a day - 80.5 watts * 24 hours = 1932WH
Batteries only store 60% of the power used to charge them. The sun only shines half the day. - 1932/2 + 1.4 * 1932/2 = 2318WH
the panel has 12 hours to collect all that power - 2318WH/12H = 193W

You need a 200W solar panel to power your 70W computer each day. This does not take into account dust, clouds, shade.

A 190W solar panel cost $900 Link

I'd rather get a start up/shut down controller...

20mg · 06-14-2008, 02:00 PM

i am still looking into it. so far i have used the solar panel i have to run my gps just to make sure there was even enough current for that. there was by the way! i kinda got distracted with another project tho. and no my battery hasnt died yet i have an optima in the hatch i just think its kinda a waste to have my car sitting in the sun for 8 hours a day and not be using any of the energy thats shining on it ya kno?

Seth_jxl · 06-15-2008, 02:40 AM

its amazing how much energy the sun puts into your car, i completely agree with you 20mg. However when using a combustion engine the waste is really under your bonnet don’t you think?
I think a car like the Toyota prius could really use a few solar cells on the roof to keep the battery topped up when its stored, it could only lengthen the life of the batteries.
I guess if you look at it in an extreme way, you are saving a little bit of petrol by reducing the load on your alternator which in turn reduces the load on your engine/petrol consumption, but i think you would be looking at something like 0.1L of each tank at best lol.