3 Watt Solar Panel

[Bad Obsession]

Since my boat is spending a lot of time on her trailer right now (I plan to keep her on the trailer this year and put her in a slip next season) I bought a small 3 watt solar panel to keep the battery topped off without having to plug it in.

I am thinking that this is a good size panel for my 1 group 27 battery. Eventually I will have 2 group 27 batteries on the boat and I think that this will do an okay job at keeping them topped off.

As far as power consumption, I have no idea on what I will be using. My devices that I will be running most of the time will be a tiller pilot (Simmerad TP-10), depth finder, Garmin GPS Map 441s, and a stereo. At night I will run an LED anchor light and a Camafro fan. Most of the cabin lights are LED.

My outboard will do some charging since I have an alternator. I will probably leave the 3 watt panel plugged in just to get a little extra power coming in.

All in all I think that my power consumption will be moderate. My goal is to be able to sustain my small battery bank at an acceptable level for a week or so of cruising without having to plug in at a dock.

Does it sound like I have an acceptable system here? Is there anything that I should watch for with the solar panel? Will I run any risk of overcharging my battery if I leave the boat for a month or so on the trailer with the solar panel plugged in?

 

[jepomer]

3 watts x 5 hours/day = 15 watt-hours per day (effective usable sunlight)

This works out to be about 1 amp-hour for a 12 volt battery per day replacing what was used.

This will be fine for keeping the battery "topped off" but don't expect to recharge the two group 27 batteries.

Go to a larger solar panel.

I use 115 watt panel to recharge four GC2 golf cart batteries to power a Torqeedo Cruise 2.0 electric outboard plus a Group 24 house battery. The two different charge controllers optimize the solar energy conversion. It takes a couple of days to recharge the batteries when I bring the level down to 50% discharge. My boat is on a mooring and never gets a shore charge.

 

[Bad Obsession]

The main reason for the panel is to maintain the battery charge. I have a battery charger on board for plugging in and I also have an alternator on my outboard.

With the current group 27 I just want to keep things topped off as much as possible when she isn't in use. Sitting on the trailer or in a slip and not plugged in to shore power leaves little option but something to keep a charge going as a slow rate.

The good thing is that the outboard is manual start so if I kill the battery I am not stuck. It is just a big pain in the butt because I will have no power!

 

[mitiempo]

I think any panel worth having needs a controller. A 3 watt panel isn't really worth having - its use is really just to maintain a battery on a car when not in use. As jepomer posted at best it will give you 1 AH per day. As far as actual charging it is useless.

I would get a 20 watt panel and a basic controller. Not only will it maintain your battery but you will get some meaningful amperage out of it.

 

[Bad Obsession]

I ended up taking the panel back. I bought a 5 watt panel.

This is just for keeping the batteries topped off. I could have gotten a 15 watt panel for a good price but it would have been hard to find a place to mount the panel. It would have also gotten expensive.

I will see how this 5 watt panel does for now and re-evaluate later.

 

[Benny17441]

Yes, that is a trickle charge which may just be adequate to maintain the batteries and nothing else. That is if there is adequate sunlight. If you do not use a controller then at night current will be flowing in a reverse direction from the batteries to the cells thus enhancing the natural rate of discharge.

 

[Bad Obsession]

The panel has a built in controller that prevents overcharging and discharge when it is not active.

I agree, having a larger panel would be nice. Right now it is a little out of my budget and not on the immediate to do list. I also have an issue of where to mount a panel where it won't be in the way.

 

[Sumner]

The panel has a built in controller that prevents overcharging and discharge when it is not active.

I agree, having a larger panel would be nice. Right now it is a little out of my budget and not on the immediate to do list. I also have an issue of where to mount a panel where it won't be in the way.

Not sure what the budget is but for about $90.00 total (and a little freight) ....

http://www.solarblvd.com/Solar-Pane...40-Watt-12-Volt-Solar-Panel/product_info.html

you could have a 40 watt panel ..... and ....

http://www.solarblvd.com/Charge-Con...,-12V-Pwm-Charge-Controller/product_info.html

... a controller.

Wire the controller to the battery (2 wires) and buy an outdoor extension cord and cut it in two near the female end. Wire the female end to the controller and wire the male end with the longer cord to the panel (2 wires).

Now you can just leave the panel in place laying in the cockpit where it would get sun when you aren't there and unplug it if needed and store it while out. While unplugged I'd put a female plug (not connected to a wire) on the male end to protect it and to make sure it didn't short on something.

For not much more you could move to a larger panel and a better controller. $20 more and the same controller would get you a 60 watt panel. Over that and you would need a larger capacity controller but another $20 there would let you move to a much larger panel (140 watts or so),

Sumner

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[The Garbone]

I ended up taking the panel back. I bought a 5 watt panel. This is just for keeping the batteries topped off. I could have gotten a 15 watt panel for a good price but it would have been hard to find a place to mount the panel. It would have also gotten expensive. I will see how this 5 watt panel does for now and re-evaluate later.

That it's what I did on my 27. Used 2 Magma grill brackets to attach it to my stern pulpit. The brackets cost more than the controller and panel. The 15 was good for about 4 days of continuous use here in Florida before we would pull in to top off on shore power. By that time a nice long hot shower in the marina was welcome anyway.

 

[Bad Obsession]

Good suggestions.

I think my current solution is to keep the 5 watt solar panel plugged in when I am not at the boat (it has an overcharge protection and protection from draining when not in use). I can probably leave it on deck when underway too.

When I go up to a 30 watt panel (or somewhere around that neighborhood) I will look for the best place to mount it on a semi-permanent mount. It is still tempting to spend the money and have it attach to the bimini (semi-flexible panel) so that it is there when the boat is in use and then put it on the deck or cockpit when I am not there.

Small boat calls for smart solutions.