Solar Pannel for 1 battery

Ross · Dec 5, 2008

Todd , the answer to most of your questions is, It Depends. It depends on what you mean by small (3-5 watts is my idea of small). It depends on how long you burn the lights and play the radio. And it depends on how often you use the boat. add up the watts of the lights and figure the hours you use them. Balance that against the hours of sunlight on the panel times the rated output, keeping in mind that the panel will only be in an ideal position for a few hours each day. As you can tell it depends on many factors.
It is sort of like asking, "can I keep my dog fed on table scraps?" The answer to that is," how big a dog and how wasteful is the cook?"

sailingdog · Dec 5, 2008

Well said Ross..

It also depends on where you're sailing. If you're sailing in the UK or in Seattle, where overcast skies are predominant, then solar might not be a great solution. If you're sailing in sunny San Diego, then it might make more sense.

Also, are the nav lights LED based or Incandescent based? The LED-based nav lights draw a lot less power.

Ctskip · Dec 5, 2008

For a trailer sailor I'd go to E-Bay and look up solar panels in the automotive section. Volkswagen sends their new vehicles out with a throwaway solar panel that is intended to keep the battery fully charged till the new owner takes it over.They plug into the lighter on most. some don't. The amount of charge is small, ands it's solar . It might work . For under $25, I would think it'd be worth a shot. If not recharge it in the driveway and get a second one. If thats not enough get a third one. Whats there to lose? Why spend $300 if you don't have to?

Keep it up,
Ctskip

caguy · Dec 5, 2008

I think the general consensus in the last thread to this question was that money was better spent on increasing your battery storage by adding another battery. In order to meet your needs you would need at least a 20 watt panel. If you are planning a 4 day weekend two 90 amp deep cell batteries would give you enough.
Someone may want to correct me on this but to the best of my recollection you should not mate a new battery with an old one, but if you keep them separated via a switch you would be able to use both batteries, one as a back up.
After the feed back I got from my posting I returned the 7.5 watt panel to WM. and will buy a second battery.
Hope this helps.
Frank

Ian4781 · Dec 5, 2008

IT DEPENDS...is the best answer....I had a 5.5 watt panel to charge 1 battery and ran a MinnKota outboard on an O'day Mariner.I never touched the battery during the 3 years I sailed the boat other than winter removal and storage and in that time I never lacked power,however,I must admit that I did not use the electrical system very much.I am now in the process of refitting my Pearson 26 and will certainly be hooking up a solar panel system

Pink Flamingo · Dec 5, 2008

Ian, I know this is outside the thread,but I am wondering about the minn-kota on your Mariner.I need some kind of motor and am thinking of a Minn-kota Endura 55.
What is your experience with this setup.

Roger (Ninette Manitoba) · Dec 5, 2008

my experience with one battery, one panel...

I have an almost identical system to yours. One group 24 deep cycle battery that runs two 10 watt nav lights, an led interior light, a seldom used spreader light and the whole system maintained by a 6 watt solar panel. Here are the complicators... If you run those lights every evening and night, the system will eventually die. If you only run the lights on weekends and the solar panel charges throughout the week you will likely be fine. I note that I occasionally need to ac charge my battery once in mid season, usually following a late night using lights, and especially the 55 watt spreader light.

My radio is a portable VHF with internal batts. My am/fm runs on its own AA's or hand crank. My anchor light is a self contained LED that runs on AA's a well. My GPS runs on its internal AA's. I carry spare AA's as a backup. I am also a minimalist, but you have probably figured that out already. I don't have the luxury of shore power to replenish my 12v batt during the week.

Hope my experience is helpful.

Stu Jackson · Dec 5, 2008

Another way to say what's been said, especially roger's, is do an energy budget. How much out compared how much comes in from the panel. Do the math.

Big Easy · Dec 6, 2008

Todd, everything that everyone has advised to this point is correct. But you are not a blue water sailor or you would not have asked the question, so why bother . . . and wonder . . . and worry?

To remove all doubt as to whether you have enough power, spring for a Honda 1000 for about $700 or so. Then when you wake up in your favorite anchorage Sunday morning you can charge your battery, brew a cup of coffee, and watch the morning news - - all at the same time. Plus you will have the generator for other uses ashore. I use a Honda 2000 on my Hunter 35.5 to run the microwave, TV, Mr. Coffee, etc.etc. I think the 1000 weighs about 25 pounds and you cannot believe how quiet they are.
a joyner

sailingdog · Dec 6, 2008

Of course a solar panel is much lower maintenance and poses no risk of CO poisoning.

Ross · Dec 6, 2008

Let's do the math, $700 for a generator or $30 for a solar panel at 4 watts ? $120 for four solar panels for 16 watts. Throw in $60 for a caterer's portable propane stove to make coffee on, or buy a $10 fuel can for the genny. $710 - 180= $530 not spent. With payroll taxes at 35% that becomes $815 that you didn't have to earn.

Joe11688 · Dec 6, 2008

Scubajeep said:
I have a 1996 23.5 hunter with an outboard without a charging system. I looking to hook up a solar panel to my sailboat battery. To keep it toped off and hopefully charge it up a little. I have 1 12 volt battery used for cabinlights, nav lights and mast light. Does anyone recommend a specific brand? Also will a small pannel keep the battery charged if I hook up a radio to it?

Thanks
Todd

Todd,
I'd go for a solar panel with the largest output that that can be had for the least amount of money. One, 100 Amp Hour deep cycle battery should should surfice, provided that you don't use your cabin lights all the time, and your running lights some of the time. Also, instead of using an anchor light at night, you can pick up a self contained solar powered light to hang in the stern. To tell you the truth, I don't even use my anchor light in the coves that I spend my overnighters in. I usually anchor in shallow places that other boats can't get into. I have a charging system on my outboard, but I don't have a solar collector on board. With that said, I never turn on my cabin lights except for a short duration. I keep a flashlight on board, and I use two candles at night in a quiet anchorage. I read with a battery powered round LED light in the V birth. I use my VHF occasionally when I need to open the draw bridge, but outside of that the only other draw on my battery is my Autohelm ST1000+ which I use about 99% of the time when I'm sailing. You need to figure out the load on what you are using for power. If you have a 15Watt bulb for each of your running lights, you can figure out the load in Amps by using Ohm's Law. P=VI. P stands for Power or Watts, V for Voltage and I stands for current. To convert Watts to Amps, the fomular would be I=P divided by V, or I equalls P over V. After you total up the load in Amps, you add the total use of hours. This will give you the Amp Hours on a typical cruise. Like some of the guys have mentioned in this thread, if you can convert the incandescent bulbs over to LEDs, the power consumption will be greatly reduced. I have a junky old battery powered radio that I listen to on board and I'm always consious of electric power usage on my boat. So far, this past year I haven't had to recharge my battery with shore power. My outboard has done a pretty good job of keeping my battery up, but I don't see any reason why you can't do the same thing with a 5 Watt solar collector, provided that you conserve power.
Joe

flhunterowner · Dec 6, 2008

solar

Is the radio a stereo or a marine vhf? If you use a trasmitter, it will use more power when transmitting. Receiving is prob. about the same.

I installed 2 15watt solar panels and a charger on my hunter 30. With everything (including alumn. framing i fabricated, I have about 300 dollars in it.

They keep my batteries fresh and provide me with power to run 3 lights and 2 fans (when not charging batteries).

Of course I live in Florida,so the sun is stronger here.

The information provided previously is spot on. Do the calculations and the output is proportional to the suns strength

Ross · Dec 6, 2008

Re: solar

Scubajeep is in louisiana. Therefore the angle of the sun is not a factor.

walt · Dec 7, 2008

If you have Microsoft Excel on your computer, you can try this power management spreadsheet here:

http://analogengineering.com/sail/sailboat_power_management.xls

Its power management for a sailboat with somewhat of a focus on solar. Its gotten a litte complicated (recently added effects of battery self discharge - suggested by sailingdog and others is a different forum). You can change any value in purple and see how the calculated red values are changed.

There are a bunch of items in the loads section and if you dont have these items, just enter zero for the daily hours used. If you have a load which is not shown, there are some spare entries. The spreadsheet is hopefully flexible for different configurations.

I "think" its all ballpark but would be happy to attempt to expain why or where any of the calculations came from.

http://analogengineering.com/sail/sailboat_power_management.xls

Fairwind · Dec 7, 2008

15 watt panel =1 amp charging current in full sunlight. A 24 size deep cycle battery=70 amp/hours. A #27 deep cycle=100 amp/hours capacity.

If you want to actually charge a moderately discharged battery, you will need at least 50 watts of solar panel capacity to do the job. That will provide 3.5-4.0 amps of charging power. A 15 watt panel will maintain a charged battery that sits unused for long periods of time.

Ross in Tampa · Dec 8, 2008

NO NO NO...

The clip on solar powered lamps are NOT a substitute for an anchor lamp. They are great, and are very useful to light up your cockpit, but will not and cannot be used for a anchor lamp. No more than taping a flashlight to the bow that has been tinted with sharpy as a red/green bow light.

sailingdog · Dec 8, 2008

Just remember, if you're not anchored in a designated anchorage area and get hit at night and are not using a USCG certified anchor light, there's a really good chance that you're going to get sued and lose your shirt in the lawsuit. Not having proper navigation or anchor lights is a good way to take on extra liability for an accident. Most solar powered lights are not sufficient to be used as an anchor light by themselves.

If you really want to be conscious of your electrical usage, get an LED anchor light. Doing what Trinkky recommends is foolish and dangerous IMHO.

Trinkky-Dinky said:
Todd,
I'd go for a solar panel with the largest output that that can be had for the least amount of money. One, 100 Amp Hour deep cycle battery should should surfice, provided that you don't use your cabin lights all the time, and your running lights some of the time. Also, instead of using an anchor light at night, you can pick up a self contained solar powered light to hang in the stern. To tell you the truth, I don't even use my anchor light in the coves that I spend my overnighters in. I usually anchor in shallow places that other boats can't get into. I have a charging system on my outboard, but I don't have a solar collector on board. With that said, I never turn on my cabin lights except for a short duration. I keep a flashlight on board, and I use two candles at night in a quiet anchorage. I read with a battery powered round LED light in the V birth. I use my VHF occasionally when I need to open the draw bridge, but outside of that the only other draw on my battery is my Autohelm ST1000+ which I use about 99% of the time when I'm sailing. You need to figure out the load on what you are using for power. If you have a 15Watt bulb for each of your running lights, you can figure out the load in Amps by using Ohm's Law. P=VI. P stands for Power or Watts, V for Voltage and I stands for current. To convert Watts to Amps, the fomular would be I=P divided by V, or I equalls P over V. After you total up the load in Amps, you add the total use of hours. This will give you the Amp Hours on a typical cruise. Like some of the guys have mentioned in this thread, if you can convert the incandescent bulbs over to LEDs, the power consumption will be greatly reduced. I have a junky old battery powered radio that I listen to on board and I'm always consious of electric power usage on my boat. So far, this past year I haven't had to recharge my battery with shore power. My outboard has done a pretty good job of keeping my battery up, but I don't see any reason why you can't do the same thing with a 5 Watt solar collector, provided that you conserve power.
Joe

flhunterowner · Dec 8, 2008

solar charging

Informative article written by Don Casey on charging your batteries using solar.

http://www.boatus.com/boattech/casey/30.htm