Solar panels

alexco38 · Nov 10, 2008

0.29 amp is not going to kill your battery. I have a 13w panel and it barly bring the voltage above 13.8v for a group 27 deep cycle battery.

sailingdog · Nov 10, 2008

Depends on the size of your battery bank and the voltage of the panel... but in most cases, no, it probably won't fry your batteries. However, if your bank is large enough, it won't keep it topped up either.

ITMaster · Nov 10, 2008

Plus Also, Correct Me Sailingdog if I am Incorrect,

Any charging mechanisim should be outfitted with a proper voltage regulator, the purpose of which, is to prevent overchaging of battery systems. Sailingdog is correct, a 3.5 watt supply will do very little for a battery bank. When you plan electrical load and availability recall the formula, Watts/Voltage=Amps
This will help you determine what you can expect

Ross · Nov 10, 2008

I believe that these panels are sized to match the load of the never shut off electronics. Things like the receiver for the door locks, the clocks, the sensor for the anti theft system etc. I doubt that they were ever expected to replenish a depleted battery.

Ross · Nov 10, 2008

Connect it to your own fully charged battery and and check the out put current in full sunlight. I rather doubt that it will deliver 3.5 watts to a fully charged battery I expect it to reach equilibrium.

sailingdog · Nov 10, 2008

Ross-

Just remember it may depend on what battery chemistry the batteries on the boat are. Wet cell batteries can self discharge as much as 1% per day... and a 3.5 Watt panel, even going full tilt, isn't going to offset that on a larger battery bank...

Ross · Nov 10, 2008

sailingdog said:
Ross-

Just remember it may depend on what battery chemistry the batteries on the boat are. Wet cell batteries can self discharge as much as 1% per day... and a 3.5 Watt panel, even going full tilt, isn't going to offset that on a larger battery bank...

These panels were chosen for size based upon a single automotive battery for a larger battery bank I should think that a larger panel would be in order. It is interesting that my AGM group 31 batteries loose only about a quarter volt from December to April while sitting in my boat. As you say a lot depends upon the type and chemistry of the batteries.

Florida sail · Nov 10, 2008

I like my set up

Ctskip said:
I just read on a post here about a solar panel, 3.5 watts, I believe. VW has them in all their new vehicles to keep the batteries topped off during prolonged storage and shipping.
If I were to leave this panel connected to my battery, would it just charge the water right out of it, and prematurely kill my battery in a matter of weeks? It sounds to good to be true. So I was thinking maybe, just maybe, it is. Any comments? Thanks.

Keep it up,
Ctskip

I have a 24 watt permanently mountedon my cabin top slide. I have an in line charge controller for my group 27 deep cycle. This has woked for me. I do not use much 12 voot other than my VHF and my running lights.
>>ron<<
S/V Serenity

sailaway78 · Nov 10, 2008

Small solar panel

Seadance and her hubby have one of these on their boat, and it works well for them. They have two deep cycles, not sure whether group 27 or 29. You might drop Seadance a line and ask about theirs.

sailingdog · Nov 11, 2008

AGMs have a much lower self-discharge rate and the lower the temperature—the lower the self-discharge rate generally is. The 1% per day figure for wetcells I mention above is for summer temperatures generally.

Ross said:
These panels were chosen for size based upon a single automotive battery for a larger battery bank I should think that a larger panel would be in order. It is interesting that my AGM group 31 batteries loose only about a quarter volt from December to April while sitting in my boat. As you say a lot depends upon the type and chemistry of the batteries.

Stu Jackson · Nov 11, 2008

C'mon, asking about solar here without anyone suggesting:

1. West Marine Advisors - online and in their catalogs

2. Using this site's search engine - there have been many, many solar posts, most with great links to solar applications for boats

3. Google???

4. http://store.solar-electric.com/1to39wasopa.html

5. http://discoverpower.com/shop/solar_panel_photovoltaic_module_low_price_electric.asp

This list is endless...

Stu Jackson · Nov 11, 2008

The reason I suggested the WM Advisors is that they discuss the size of the panel related to the size of the battery bank(s) and the implementation of or need for controllers based on that ratio. I don't know if the Volkswagen brand on it was part of your question.

3.5 watts is tiny and you could probably use it without a controller on even a small 60 ah battery without either damaging the battery or doing much charging.

Ross · Nov 11, 2008

Stu, These solar panels are used by VW but they are polycrystalline Photovoltaic panels with no obvious makers name. Brand name is insignificant in this case. The real question was will a tiny 3.5 watt solar panel have a deleterious effect on a battery in the long term? I believe that your last post answered the question quite nicely. These panels are very available because you get one with each new car. They come with a plug for a cigarette lighter socket and are a throw away item when the car is delivered.

Will Sail For Food! · Nov 11, 2008

Stu Jackson said:
C'mon, asking about solar here without anyone suggesting:

1. West Marine Advisors - online and in their catalogs

2. Using this site's search engine - there have been many, many solar posts, most with great links to solar applications for boats

3. Google???

4. http://store.solar-electric.com/1to39wasopa.html

5. http://discoverpower.com/shop/solar_panel_photovoltaic_module_low_price_electric.asp

This list is endless...

Just the opinion of a newbie lurker here, but you guys seem to come down hard on people for not searching the archives. It seems to me there wouldn't be much activity on this board if everyone just searched the archives and went away. JMHO

Hermit Scott · Nov 11, 2008

'Will sail for food'...your question about searching the archives is in the archives. YOU SHOULD HAVE LOOKED THERE FIRST!!!!!
Just kidding. I sort of felt the same way when I first came here. There was one dude that was like the archive police.
I bought one of these small solar panels because I read that leaving a battery in any state of discharge will casue sulfation(where the lead in your batteries combines with the sulfur and falls to the bottom of the battery and is of no use anymore). The worse the state of discharge the worse the sulfation. Initially the sulfate crystals are soft and are easily converted back to usable lead on the plates and sulfur in the electrolyte. After a while though they harden and are more difficult. The book says having even a small charging current flowing into them will prevent this.
Leaving your boat sitting for 3 months with out a charging current will result in a permanent loss of capacity. Better to have a charging current too low than too high.
This is actually alot more complicated than I have it here. I recommend you get a book on sailboat electrical system. I got 'Sailboat Electrics simplified' by Don Casey on ebay for $5. There is a lot to understand about batteries and charging systems that is not generic information. You will have to calculate it for your use of your electrical system.

Allan12210 · Nov 12, 2008

I bought several of these. They are made by ICP. The ones with the OBDII connector have a built in controller. After replacing the connector with a cigarette lighter plug, it has kept my old car topped off for over a year. Haven't had the need to replace water in the battery and it starts right up (with a little coaxing).

I am going to dedicate one of these to my starting battery. I like the eco solution, plus it gets me out of the quandry of sharing my charger (both the Xantrex and alternator) with mixed battery types. If I end up cranking too much (I doubt it) and the starter battery gets depleted, I can still always switch to the house bank.

As a non-battery aside, I put another VW charger on our H34 in front of the dorade vents. Run the wire through the vent. Inside the boat, I mounted two computer muffin fans inside the wood panel where the dorade vents are. I put the two 110ma 12V fans in series and bypassed the controler to get about 22 volts. They seem to have had a positive effect on the freshness inside the boat. It was a lot cheaper solution than the Nicro solar vents. I spent about $40 for the whole thing and didn't have to drill any holes anywhere except to screw the muffin fans to the topside of that wood panel. Nice to be able to scrounge around the electronic surplus places here in Silicon Valley.