solar panels

[rosser1]

has anyone had any luck with putting solar panels on their boat to charge batteries? thanks for the input!!

 

[LippCJ7]

Re: solar panels

I hope you have a big boat! as most will tell you, you will need a very large solar array to charge your batteries in a decent amount of time. If your talking about setting a standard 18" solar panel on your boat during the week while you work it will probably do some good for the weekends but on a daily basis you will most likely not see much of a difference at all.

 

[DianneB]

Re: solar panels

I put a 20 Watt panel and charger on my engine battery to ensure it stays up for the bilge pump during the week when I am not there and it seems to work pretty good. The fringe benefit is that the engine starts like the battery is fresh every time. I plan to add a 200 Watt panel for the house battery to keep the house battery up and the fridge cold for extended outings. For that one, I am using a controller with a low-voltage disconnect so the fridge doesn't kill the battery if I get a few cloudy day.

 

[Bob_VT]

Re: solar panels

The panels are allot of money and if the boat is trailered I do not feel they are worth the investment. I use a battery maintainer.

 

[keninaz]

Re: solar panels

Just to add to what has already been said, you also need to clean them to keep dust and dirt off of them. This reduces their efficiency.
I have also seen people install these without regard for UV protection for the wiring and the sun quickly rots the insulation off the wires.
If you have a bigger boat and can put up enough panel to keep your batteries up that's fine. But they do require some attention.
If you have AC available your are much better off with a true automatic battery tender. I know people that have classic cars that they leave one of these on and it's always ready to go. And the install is easy and the price is good.

http://www.amazon.com/gp/product/B00068XCQU/ref=oss_product

 

[rosser1]

Re: solar panels

the panels are small but put out .87 volts at all times, i am going to put them one going to starting battery and one to trolling. to keep the batteries charged while on the water or while sitting uncovered in yard. I think it will work pretty good.

 

[Silvertip]

Re: solar panels

the panels are small but put out .87 volts at all times, i am going to put them one going to starting battery and one to trolling. to keep the batteries charged while on the water or while sitting uncovered in yard. I think it will work pretty good.

if all the panel puts out is .87 volts you will have a long wait and dead batteries. I think you mean .87 amps. And If you expect .87 amps to have an effect, especially for a deeply discharged trolling motor battery, you will still have a long wait. Lets run some numbers. A 40# trolling motor draws about 40 amps at full speed. So in one hour you sucked 40 amps out of the battery. So if your .87 AMP solar panel has full sun, you divide .87 into 40 and the result is 46 hours. That's how long you would have to have the panel in full sunlight to replace the 40 amps you used in just one hour. You apparently are like many uninformed folks that have the idea that just because a panel puts out 12 volts it is an inexhaustable supply of energy. Well, it is as long as whatever you have it hooked to doesn't draw more current than the panel puts out. You are fighting a losing battle sir. A solar panel that would actually charge a battery would need to be the size of your boat.

 

[Moody Blue]

Re: solar panels

You apparently are like many uninformed folks that have the idea that just because a panel puts out 12 volts it is an inexhaustable supply of energy. Well, it is as long as whatever you have it hooked to doesn't draw more current than the panel puts out. You are fighting a losing battle sir. A solar panel that would actually charge a battery would need to be the size of your boat.

That is largely due to marketing hype and misleading packaging on consumer products. As an example, a commonly available panel 4" x 12" states "Charge the batteries on the boat, RV or vehicle". In reality that's not remotely possible. That panel puts out 125mA under ideal conditions. That is only 1/8th the current output of a 1 Amp trickle charger, hardly capable of charging anything larger than a AA cell flashlight battery.

 

[rosser1]

Re: solar panels

thanks for the numbers silvertip, you really shot me in the foot, but i would rather know the truth than to get out on the water with high hopes and find out the hard way. thanks everyone for ideas and advice!!

 

[Silvertip]

Re: solar panels

I didn't aim at your foot. I aimed at the truth. As another example, has anyone seen the "Solar Generator" ad on TV recently. This is strictly a solar powered battery box that contains an inverter to convert a battery pack to 115 VAC. Just how long do you think that box would power anything in the house during a prolonged power outage? At best probably an hour or two. Don't know what the cost is but I'm guessing its much more than a 5000 watt gas powered generator.

 

[rosser1]

Re: solar panels

I have a dumb question ... how many amps does it take to make a volt, i am not a good with all the numbers. just was wondering also with talking about panels if a panel with two converters put out more or two panels with one converter. or better with one panel per converter. i have a few panels and wanted to figure out the best way to put them to good use on my boat.

 

[TerryMSU]

Re: solar panels

Rosser:

Sorry, please don't be offended, but that is question is like asking how many feet does it take to make a horsepower. (Well not quite that bad, at least volts and amps are slightly related.)

Amps is the current flow, which is directly related to the number of electrons flowing past a point in a second. Volts is the electrical "pressure" that makes those electrons move. For an analogy, consider a hose with water flowing thru it. The amount of water flowing thru the hose is similar to Amps (both of which might be described as current). The water pressure making that water flow is similar to volts.

And finally, as a free-be, the term resistance is analogous to the degree to which the hose allows water to flow. Long hose has high "resistance", narrow hose also has comparatively high resistance. Similarly a long wire will have high resistance as will a wire which is too small in diameter.

TerryMSU

 

[Silvertip]

Re: solar panels

Then there is the question of what you mean by "converter". The only time a converter is required if you are trying to convert 12 volts DC from a battery into 115 volts AC to run househole appliances. If this is what you are wondering, this is exactly what I tried to point out in my last comment. There is no "free lunch" here. Solar panels don't put out much power by themselves. So an array of panels (2 or more) can be ganged to charge a group of batteries. The batteries then have a large amount of stored power and that is what powers the converter to make the AC power for house power. Keep in mind that you are using 12 volts DC to create 115 volts AC. That is nearly a difference of 10 (factor of 10) so 10 amps of input power on the converter can produce only 1 amp of power out of the converter. In other words if the device you plugged into the converter drew 10 AMPS you would have to INPUT 100 amps from the batteries. That device would suck a very large battery dead in no time at all. So you see, when dealing with electricity or power of any sort, you need to understand the numbers. Electric cars are another example of how power works. Have you noticed that pure electric (not a hybrid) have very short ranges.

 

[Moody Blue]

Re: solar panels

Have you noticed that pure electric (not a hybrid) have very short ranges.

And VERY big batteries

Rosser1, not a dumb question at all.
A simple formula that may help you understand the relationship between power (watts W), voltage (volts V) and current (amps A)

W = V x A

from which

V = W / A

or

A = W / V

 

[rosser1]

Re: solar panels

thanks moody blue, that will help. Silvertip... what i am doing is putting them on a trolling motor battery. the converter i am talking about is ...... i have a solar panel and the panel doesn't do anything by it self, it is a converter, that i guess convert sun light from panel to dc to charge battery. mostly to keep batterys up while trailering or sitting in yard. because where boat sits in yard is a long distance from outlet put to keep plugged in or on charge all the time. or while on water and trolling battery last all day anyways but thought if i could put some charge on it while out on water it would be better, so battery doesn't completly die.

 

[Silvertip]

Re: solar panels

There is no "converter". If the solar panel has an output voltage of 12 volts, you connect it to the battery and the sun does its job. The point everyone is trying to make is that the AMOUNT of electricity produced by the panel cannot possibly "charge" the battery in a short period of time. If you ran that troller all day and then connected the solar panel overnight and wanted to fish the next day, the battery would still be very discharged. Those small panels are designed to keep a battery from self-discharging. You need a very large panel to actually charge a deeply discharged battery. Having that small panel connected while on the water would not any appreciable charge. Most of those small panels are about 5 Watts output which is not enough to even light a tail light bulb from your trailer.

 

[NYBo]

Re: solar panels

If you ran that troller all day and then connected the solar panel overnight and wanted to fish the next day, the battery would still be very discharged.

And that's even with a full moon!

 

[Socal Pat]

Re: solar panels

When I go camping/fishing in the high Sierra I take along this unit http://www.harborfreight.com/5-watt-solar-battery-charger-41144.html along with 2 batteries. I can then run a trolling motor each day and use a battery to watch TV at night. After 10 days in the back country I don't run out of juice.

 

[Silvertip]

Re: solar panels

When I go camping/fishing in the high Sierra I take along this unit http://www.harborfreight.com/5-watt-solar-battery-charger-41144.html along with 2 batteries. I can then run a trolling motor each day and use a battery to watch TV at night. After 10 days in the back country I don't run out of juice.

With only 5 watts output you are not using much power from the batteries. 5 watts = 0.39 amps which isn't enough current to light a tail light bulb much less charge a deeply discharged battery. As was pointed out before, if you ran your trolling motor for one hour (depending on it's size) it would consume anywhere from 30 to 50 amps of power. That would take your 5 watt panel 128 hours of full sunlight to replace that amount of power. What I'm contending here is based on your assertions, you would also very likely not run out of power if you left the panel at home. While it would replace one amp of power every three hours of full sunlight, that amounts to only 5 amps of power each day provided that sunlight is available 15 hours each day. I have that very same panel installed in the window of my shed to keep my tractor and electric start rotary mower battery topped off during the winter months. It is not there to actually charge a dead battery because it is simply not capable of that in a reasonable amount of time.

 

[ONERCBOATER]

Re: solar panels

"30 to 50 amps of power. That would take your 5 watt panel 128 hours of full sunlight to replace that amount of power."

that is assuming a 100% charging efficiency .... not possible would take even longer in real world due to line loss ect...