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Old 09-12-2012, 15:59   #1
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Minimal electrical needs and solar panels

With all this talk about solar panels and all . . .

Aside from an electric motor, which I could toss in favor of something else if I needed . . .

I wonder why most boats even need big batteries.

I know that on my boat(inboard gasoline and outboard electric), I use electric for lights, an AM/FM radio, the VHF and sometimes for fans.

Newer VHF radios are quite stingy on wattage use, while I've got a couple of handhelds that need batteries changed about every other year.

I've learned to get by without fans if possible, although a small fan on my face at night is nice.

All my interior lighting is either oil lamp or a grand total of about 6 watts of LED lighting.

My nav lights are about 4-6 watts of lighting.

Both my indoor and nav lights can just as easily run on 3 volts using AA batteries.

I run my cabin lights about 2 hours a night during the summer and in the fringe months of March-April and October-November, I run them about 3 hours a night.

I use very low lumen LED's for all night "nightlight", but very rarely at that.

If I could crank start my engine, which is not unheard of for an Atomic 4, my total electrical use would be very, very negligible.

Almost to the point that any solar panel wattage over 10-20 watts would be complete overkill. Of course I like to have a buffer.

I surmise my electric O.B., moves me at about 2 knots for probably less than 10 amps or so an hour . . . just a guess . . . I don't really know. So if I use this motor only as I always intended, I might have to account for a couple hours use on those days I use it.

This would put discussion about solar panels, for me, in a whole new light.

This might mean that worry about size, angle of attack and partial shade would become much less important.

This could possibly mean that the need for permanently mounted panels could be avoided altogether.

In many ways this seems like it could be really nice.
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Old 10-12-2012, 07:06   #2
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Re: Minimal electrical needs and solar panels

The rule of thumb that I've seen before is that $1 spent reducing consumption is worth $5 increasing generating ability. Seems you've got a good handle on reducing consumption. A whole lot of people, on the other hand, would rather just throw money at bigger panels (or whatever) than try to make any adjustments of their consumption.
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Old 10-12-2012, 08:51   #3
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Re: Minimal electrical needs and solar panels

Sorry, mate, that particular rule of thumb is obsolete nowadays.
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Old 10-12-2012, 08:55   #4
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Re: Minimal electrical needs and solar panels

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Sorry, mate, that particular rule of thumb is obsolete nowadays.
I am sure people would like to hear an explanation.
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Old 10-12-2012, 09:20   #5
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Re: Minimal electrical needs and solar panels

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Originally Posted by SURV69 View Post
With all this talk about solar panels and all . . .
...........
I wonder why most boats even need big batteries.

.................
In many ways this seems like it could be really nice.
Watermaker, autopilot, microwave, hot water, electric pumps (plumbing), washing machine, icemaker, fridge, freezer, TV, chartplotters..... what have I forgotten!
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Old 10-12-2012, 09:22   #6
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Re: Minimal electrical needs and solar panels

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I am sure people would like to hear an explanation.
Personal experience, personal costs, 2 years living aboard in the tropics with current system, made the mistake of swapping out the old lights for LEDs while also paying $1.50 - $1.65 per W for solar panels. Total of 970 W of panels and 90% LEDs. Then I did the sums and realised my mistake. Would have been cheaper to leave the incandescent lights where they were and simply buy an extra panel and another battery.

It's just maths and historical experience, all the info is out there.

That old rule of thumb was from another era when panels were costly.
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Old 10-12-2012, 09:33   #7
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Re: Minimal electrical needs and solar panels

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Watermaker, autopilot, microwave, hot water, electric pumps (plumbing), washing machine, icemaker, fridge, freezer, TV, chartplotters..... what have I forgotten!
Laptops
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Old 10-12-2012, 09:51   #8
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Re: Minimal electrical needs and solar panels

Your consumption is low, but you are are still going to find it tough with only 10-20w.

The one exception is electric outboard, its got a high consumption. If you want to use this with any meaningful replacement of the power from solar you need to fit the largest wattage you can.

The best option is to do an energy budget input the length of time you need for each electrical appliance. Don't forget anchor lights, phone and computer charging if these are applicable.

AA dry cells are an expensive form of power, you can use rechargeable batteries, but then your back to generating the power.

Many boat owners dream of powering their boat on small solar panels. Some realistic and simple calculations will show if the dream matches the reality.
Unfortunately it rarely does.
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Old 10-12-2012, 10:16   #9
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Re: Minimal electrical needs and solar panels

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Watermaker, autopilot, microwave, hot water, electric pumps (plumbing), washing machine, icemaker, fridge, freezer, TV, chartplotters..... what have I forgotten!
Radar, depth sounder, wind instruments, ssb/ham, ---
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Old 10-12-2012, 13:15   #10
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Re: Minimal electrical needs and solar panels

I found a mix of make&save works fine. Our new tri-color is LED. Our solar is twice its original capacity. Our batteries are half their original capacity. Things work. Make more, use less, store less. b.
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Old 10-12-2012, 22:14   #11
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Re: Minimal electrical needs and solar panels

Live aboard in Mexico - full time for 3 years and over 950 nights at anchor. At one point we spent 450 consecutive days anchored out. We commonly went for 35 - 40 days with no re-provisioning and no visit to any kind of store or tienda.

Additionally I spent about 90 days a year on the hook when not cruising full time - a lot was in the winter in Puget Sound.

There is a huge difference in what electrical power you need for the occasional one week cruise in US waters and what you need for full time on the hook live aboard in the tropics.

When we were planning the full time cruise to Mexico there were two things my wife said she would not tolerate hearing:

"We don't have enough electrical power for...."

"You can not take a shower 'cause we don't have enough water"

Amp hours / day
refrigerator - 35 ( cold beer, ice cubes & frozen meat)
water maker - 25 ( can never have enough fresh water)
computer - 25 ( I am a real computer geek and addicted )
TV/DVD - 10 (when it's your full time home you need the amenities)
anchor light - 8
other lights - 24
SSB/HAM - 6 ( e-mail and I was a controller on 3 nets much of the time)
microwave - 15 (too hot to use propane much of the time)

About 150 amp hours / day on the hook

Underway the radar used 5 amps / hour and the autopilot uses 3 per hour

winter time Puget Sound cruising (7 hours of daylight and 35 - 45 degree air and water) I used an Ardic diesel heater that consumed 20 - 40 amp hours per day.

I have four 125 watt panels and 625 amp hours of battery capacity and have never regretted the solar panels I installed 13 years ago.

My panels are rigidly mounted on an arch over the rear of the cockpit. I consistently saw over 25 amps at 14V for over 4 hours a day in the Mexican winter and 31 amps at 14.4V during the Mexican summer. Our batteries were always full recharged by 2 PM at which time we started the water maker running and forced the refrigerator to run full time to hard freeze the expansion plate. We could usually run both the water maker and reefer for two hours while still trickle charging the batteries.
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Old 10-12-2012, 22:26   #12
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Re: Minimal electrical needs and solar panels

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Live aboard in Mexico - full time for 3 years and over 950 nights at anchor. At one point we spent 450 consecutive days anchored out. We commonly went for 35 - 40 days with no re-provisioning and no visit to any kind of store or tienda...............

..........I have four 125 watt panels and 625 amp hours of battery capacity and have never regretted the solar panels I installed 13 years ago.

My panels are rigidly mounted on an arch over the rear of the cockpit. I consistently saw over 25 amps at 14V for over 4 hours a day in the Mexican winter and 31 amps at 14.4V during the Mexican summer. Our batteries were always full recharged by 2 PM at which time we started the water maker running and forced the refrigerator to run full time to hard freeze the expansion plate. We could usually run both the water maker and reefer for two hours while still trickle charging the batteries.
Very good info, thanks ,

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Old 10-12-2012, 23:00   #13
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Re: Minimal electrical needs and solar panels

Unless you are near the equator or have the Sun directly overhead, the panels don't always produce what they are rated for. I have 1680 watts worth of panels, but they only get up to 800 watts on a sunny day in Ohio during December.

So, I would get 4 times as much solar panels as your daytime demand would be. Plus another 2 times to cover night time demand (and reduce those numbers as much as you can).

Batteries just help you to have power when you really need it. And you don't want to fully drain the batteries everyday either.
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Old 10-12-2012, 23:24   #14
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Re: Minimal electrical needs and solar panels

If, say in tropical waters, is a salt water shower with fresh water rinse out of the question? A bit solar heated of course.

Is it just me?
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Old 11-12-2012, 02:44   #15
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Re: Minimal electrical needs and solar panels

When I count in my batteries is while I'm underway. Hand steering 24 hrs a day can be tough after you've had an autopilot. I find the autopilot batteries and solar the cheapest helmsman you can hire.
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