Simple electrical system with solar for recharge

[darylat8750]

Stu is leading you the right direction.

With a self bailing cockpit and without an inboard engine with a dripping shaft I would get pretty tense and want to find out why if my bilge pump ever ran......

[bigjer40]

Think I might just simplify and buy a 30amp to 110 adapter with a $35 battery charger. Won't help much on the water but will do the job at the dock or when stored. And it's a heck of a lot cheaper.

[Boulter]

Originally Posted by bigjer40

Think I might just simplify and buy a 30amp to 110 adapter with a $35 battery charger. Won't help much on the water but will do the job at the dock or when stored. And it's a heck of a lot cheaper.

What is a "30 amp to 110 adapter"??? Oh I think it is the cord that will convert 30A dock connector to regular house receptacle.

Yes, I would think this is the way to go. I did not realize you had shore power available. I ran my little boat for up to 4 days in a row last season and never gave the battery any thought, just charged it up when I got home. Mind you I was not running AP.

Anyhow I modeled my system in Excel for the following assumptions and loads:

battery 105Ah
depth of discharge desired 50%
Solar panel 1 A in full sun mounted horizontally with 5 sun hours/day
charging efficiency 0.8

VHF 0.25 A in receive
anchor light 2 watts 0.17 A
running lights 2 watts 0.17A
music system 0.2 A
Simrad TP32 AP 0.5A

The above figures are from memory except the Simrad which I looked up on the net. Even there, my boat is so small compared to the maximum size of boat the TP32 will run, I would not be surprised if my real life load averaged half that. The panel modeled is one I already own, 15 watts nominal.

Worst case scenario I get 2.4 days :

VHF 24 hours
anchor lights 0 hours
running lights 8 hours
TP32 24 hours
cabin lights 3 hours
music 12 hours
zero solar charging

Worst case scenario as above with solar charging I get 2.8 days

Typical scenario casually cruising I get 5.2 days

VHF 12 hours
anchor lights 8 hours
running lights 0 hours
TP32 6 hours
cabin lights 3 hours
music 12 hours
zero solar charging

Typical scenario casually cruising as above with solar charging I get 7.6 days. I am planning a 2 week run in the North Channel with the trailer sailors, so I may run short and need cut down the loads. Or it may be possible to get shore power at a marina.

If your typical cruising scenario looks anything like mine, I think you will agree that up to 5 days out combined with charging at the dock is a very sensible solution.

Finally, under worst case scenario to go in perpetuity would need about 80 watts of panel. For my typical cruising scenario about 30 watts of panel. Double these for fall when the 5 sun hours/day assumption is in reality about half that.

Regards,

Boulter

[bigjer40]

Thanks Boulter! That is very similar to what I will be doing and your info is so helpful. West marine sells the adapter which also works as gfi when using electrical near water. The charger I found is small and will take up little room on the boat. I will also get a small solar panel to supplement as well.

[Boulter]

Hi:

Just to follow up...

I actually ended up buying an 80 watt panel. The thinking was that it would take the same time to hack a mount for my 15 watt panel as a larger one. Why not do it just once? The 15 watt panel might find it's way to my tractor one day. I went looking for a 40 to 50 Watt panel, but came home with the smallest panel my guy had in stock.

So I got a panel and charge controller for just over $300. It is really nice what not much money will pick up these days. It should run the boat in perpetuity in all 3 boating seasons (I don't ice boat ... yet).

I just hacked a mount out of 2x4 (spruce?) and trued the members with my jointer and table saw. The wood frame mounts on two 1/4-20 "studs" on the rail and a third stud on the hull at the bottom of the diagonal strut. The rail studs began life as a hinged rail clamp fitting where I replaced the stock screw with a longer one.

I did not want to invest time doing a real proper job until I had tried it out for a while. Plus I want to get sailing this season. There will be plenty of time in the winter to make again in a more attractive wood and stain and spar varnish it.

[darylat8750]

Good progress. Let us know how it works out.

[Stu Jackson]

Could it be that all that wood is heavier than the panel?

Nice job, though.

[Boulter]

Originally Posted by Stu Jackson

Could it be that all that wood is heavier than the panel?

Nice job, though.

Thanks. Could the mount be lighter, sure. But even this first pass is less than a half a 2x4 x 8 feet, so about 4 pounds maybe. I was mostly interested in fast because I want this round of projects to be done. Plus I wanted to test the viability of the entire scheme in terms of conflicts with other gear. I can make it light, sleek, stained and varnished next winter .

I was out for the first time this year this weekend and am quite pleased. The panel is clear of any other boat gear. I am worried though about dropping the mast onto it when raising and bringing down, so I have been taking it off for mast activity. This also has its risks, so isn't entirely satisfactory either. Plus when packing up today, the power cord was not plugged in. It is unclear if I forgot to plug it in, or it came out while sailing.

All in all very promising.

Oh and to be clear, I am not the OP. I think he went with shore power charging and decided against a panel.

Boulter

[Tashtego]

Boulter has suggested that your stereo system will draw 1/2 amp at 12 volts. Son that's 6 watts! That's not stereo, that's earphones. Ditch the stereo and bring an ipod and a handful of batteries. Second, a 3 amp solar panel will barely keep your battery charged at no load. As others have said it's a trickle charger and useless for what you want. Your principle need will be for running lights and maybe the depth sounder. If you go to LED running lights and cabin lights (not an inexpensive conversion) you may get the draw down to maybe one amp for twelve hours or 12 amp hours per day just for lights. You should also forget the tiller pilot which is a current hog and buy some surgical rubber tubing. Then learn to sail with a sheet to tiller rig. No electricity needed. Get a hand held GPS (more AA Batteries) and a hand held VHF (more AAs). I have no idea what the depth sounder uses but it ain't cheap.

You are not likely to ever bring your battery to 100% charge because it takes 8 to 12 hours to fully charge. So you should plan on charging to around 90% and drawing down to about 50% or a usable amount of 40% of your battery's amp hour capacity. This means that with a 100 amp hour Group 31 battery you can use about 40 amp hours before recharging. Discharging below 50% will seriously shorten the useful life of your battery and charging above 90% is not a reasonable goal for daily use. You also need some reserve capacity for two or three shady/rainy days in a row. You need to add up all the electrical demand in your boat, convert it to amp hours and find out what solar panel wattage you need. A simple (and not very accurate but conservative) rule is that solar cells will produce about 80% of their rated output for 8 hours per day. So say a 100 watt panel will produce around 80 watts for 8 hours or 640 watt hours per day. Divide watt hours by volts to get amp hours. The charging voltage of your batteries will be around 14 volts so a 100 watt panel can produce around 44 amp hours per day. So a 100 watt panel can recharge your Group 31 battery from 50% to 90% in one sunny day. If you maintain a two or three day reserve for bad weather you can expect to support 15 to 20 amp hours per day. I agree with the recommendation to get a controller, probably an MPPT controller. An MPPT controller will give 15% to 40% more charge during a day than a PWM controller. Remember Slocum sailed around the world alone with a lead line, a sextant and a tin alarm clock with only an hour hand but he was a sailor.