Solar battery trickle charger

[Blue Pearl Captain]

I'm looking at a Sunforce 5 watt Solar trickle charger versus a Sunforce 15 watt battey charger to keep a charge in 2 12 volt in-line batteries through the winter.
It seems easier than having to remove them in case I want to do a sail on the lake in mid-winter in KY. Average temp is 35.9 deg F. with average lows of 23 deg F. Rarely do we get near 0 deg F.
oes anyone have any pros-cons to offer.
I could us mounting tips, too. Mounting location, wire routing, drilling through the hull? Can these interfere with handling maneuvers, lines, sails, travelers, etc?
West Marine has them priced at $69 (5 watt) and $109 (15 watt).
Thank you and may you have a warm winter.

 

[philwsailz]

I have used these exact solar panels for several years. I am now more a fan of the larger 15 watt panel based on long time experience. I am not sure how it will do with two batteries, as I used my 15 watt panel on a single battery. Mine stayed topped off though. My gut intuition tells me, (and this really just a recommendation based on experience, with no math considered) that the 5-watt panel might not fly for a two-battery bank.

At one point I had an old wooden Chris Craft cruiser, (leaky). The boat had a 5-watt panel permanenetly mounted and wired to the cranking battery. A second 15-watt panel was mounted along-side and connected to the house bank, where the bilge pump drew power from. This setup worked for at least three years, without ever plugging into shore power. Some will tell you these Sunforce panel are inferior, and they may be compared to the competition, but they have worked for me!

Just in case you have doubts, Ironically I have a stilll-in-the-box brand new Sunforce 15 watt panel and charge controller in my truck that came off the brown truck just yesterday. For my application, I am setting up a charging system that will use one 15-watt panel to, (hopefully) keep a dual group-27 house bank topped off, and I will use a second 15-watt Sunforce panel to keep my cranking battery topped off. I am building a smart circuit that will prevent my Blue Sea ACR from combining when solar charging, as the two banks will be dissipated at different rates, and therefore should charge at different rates. Woops, I went too far off topic!

Back to your query re: the two Sunforce options. A few things:
The 15 watt panel is large enough that you need a charge controller. Sunforce has a simple controler that to me works well for this very simple setup, and sometimes it is included with the panel. Be sure to get one if you decide to go 15 watt and your panel does not come with one. The 5-watt is low enough in power that it usually is installed without a charge controller. Know both are protected from reverse flow, (probably simply a diode) to prevent battery draining at night.

I used a non-permanent mounting for my 15-watt panel on my last C22 sailboat. I ran the power wire and plug through a small hole I drilled in the cockpit coaming. The wire can be shoved into the coaming while under way. Simply lay the panel on the cockpit seat and plug in when you get off the boat. Stow the panel when you get on the boat. This way the panel is just out of the way when you are on the boat; it stows just like your hatchboards.....

Know that the 5-watt panel will be a maintainer at best... The 15 really will be just be a maintainer too, but by its parger area and greater output will have a better chance of keeping things maintained with snow cover, dirt, shade, etc.




Were it me, given the two options you bring to the table, I would spend the extra $40.00, make sure I had a charge controller and go with the bigger panel.

Phil

 

[Benny17441]

The 5W solar charger is only rated at 350mA or less than 1/2 an Amp. With diminishing sunlight in the winter time I don't think it will do an adequate job of maintaining your batteries. These small solar panels usually lack a controller which means that at night the solar cells actually place a draw on the batteries. (Phil indicates they are protected so it may not be an issue) The 15W charger is rated for 1A and this is closer to the output of a trickle charger but once again in the winter months with diminished sunlight due to shorter days, lower sun angle, fog and cloudiness I would not anticipate you could get much more than 2-3A per day on the average. If it were me I would bring the batteries home once a month during the winter to top off and equalize and save the money.

 

[Blue Pearl Captain]

I have used these exact solar panels for several years. I am now more a fan of the larger 15 watt panel based on long time experience. I am not sure how it will do with two batteries, as I used my 15 watt panel on a single battery. Mine stayed topped off though. My gut intuition tells me, (and this really just a recommendation based on experience, with no math considered) that the 5-watt panel might not fly for a two-battery bank.

At one point I had an old wooden Chris Craft cruiser, (leaky). The boat had a 5-watt panel permanenetly mounted and wired to the cranking battery. A second 15-watt panel was mounted along-side and connected to the house bank, where the bilge pump drew power from. This setup worked for at least three years, without ever plugging into shore power. Some will tell you these Sunforce panel are inferior, and they may be compared to the competition, but they have worked for me!

Just in case you have doubts, Ironically I have a stilll-in-the-box brand new Sunforce 15 watt panel and charge controller in my truck that came off the brown truck just yesterday. For my application, I am setting up a charging system that will use one 15-watt panel to, (hopefully) keep a dual group-27 house bank topped off, and I will use a second 15-watt Sunforce panel to keep my cranking battery topped off. I am building a smart circuit that will prevent my Blue Sea ACR from combining when solar charging, as the two banks will be dissipated at different rates, and therefore should charge at different rates. Woops, I went too far off topic!

Back to your query re: the two Sunforce options. A few things:
The 15 watt panel is large enough that you need a charge controller. Sunforce has a simple controler that to me works well for this very simple setup, and sometimes it is included with the panel. Be sure to get one if you decide to go 15 watt and your panel does not come with one. The 5-watt is low enough in power that it usually is installed without a charge controller. Know both are protected from reverse flow, (probably simply a diode) to prevent battery draining at night.

I used a non-permanent mounting for my 15-watt panel on my last C22 sailboat. I ran the power wire and plug through a small hole I drilled in the cockpit coaming. The wire can be shoved into the coaming while under way. Simply lay the panel on the cockpit seat and plug in when you get off the boat. Stow the panel when you get on the boat. This way the panel is just out of the way when you are on the boat; it stows just like your hatchboards.....

Know that the 5-watt panel will be a maintainer at best... The 15 really will be just be a maintainer too, but by its parger area and greater output will have a better chance of keeping things maintained with snow cover, dirt, shade, etc.




Were it me, given the two options you bring to the table, I would spend the extra $40.00, make sure I had a charge controller and go with the bigger panel.

Phil

Thank you, Phil. Your reply was very helpful. I lean to the 15 watt but didn't know about the controller.

 

[Blue Pearl Captain]

The 5W solar charger is only rated at 350mA or less than 1/2 an Amp. With diminishing sunlight in the winter time I don't think it will do an adequate job of maintaining your batteries. These small solar panels usually lack a controller which means that at night the solar cells actually place a draw on the batteries. (Phil indicates they are protected so it may not be an issue) The 15W charger is rated for 1A and this is closer to the output of a trickle charger but once again in the winter months with diminished sunlight due to shorter days, lower sun angle, fog and cloudiness I would not anticipate you could get much more than 2-3A per day on the average. If it were me I would bring the batteries home once a month during the winter to top off and equalize and save the money.

Thanks, Benny. My thought was to use the panels in order to allo for sailing 2- times a month. That way I'd be assured a charge and would run the engine frequently enough to kep a full charge. You'v been very helpful.