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We have had unseasonal rain here on the east coast of oz which has me wondering about the sun.As my build nears it's completion I need to look at power for the boat.I have no idea about how to set this up so am looking for advice.I want a fairly basic system to power the following-

mast tricolor led

interior led x2

laptop

handheld gps

compass light

vhf

interior fans x2

bilge pumps x2

deck light

How many house batteries would this set up require what size solar panels?

thank you in advance.

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Ahoy Paul,

     The basic rule of thumb is to figure out what your daily amp hour load is, then match that with your solar panel output, usually given in watts.  Your batteries should be sized to about 3X the amp hour load.  I notice you are not including an autopilot.

     Sometimes it's hard to figure out how many amp hours you will get out of a panel, a ballpark figure is 5-6 hours a day and in my case, 45 watt panels put out about 30-35 actual watts, and this comes out to a little under 3 amps per 45 watt panel.

     A small generator can help when there is no sun.  A wind turbine can put out a lot of power and the water turbine option works well.

Hi Chuck,

Many thanks for listing the website for Paul . I have been trying various methods to work out the electrics for our boat and this link is one I can actually understand !!

Regards,

Rob.

I actually made a spreadsheet out of the worksheet using Excel. I have most of it completed It needs the final tweaking to input battery data but the daily usage data is pretty complete. I attached what I have at the moment.   

Attachments:

thank you guys,things are a lot clearer now.

cheers paul.

I'd like to thank you all also as I'm now rewiring my boat and was wondering how much power I would need.

Thanks

David

Uses 2x75A batery (stationary) and 150W solar panel...will work ok

It depends on where you are sailing: our solar panels work much better in the Med than in the UK.  We have 2 110 hour batteries, 4 ageing solar panels and a small wind generator.  With this set up we run all the things you list with the exception of bilge pumps and fans as we have neither but we do have more LED lights than you.  What we can not run unless it is strong sunlight and windy is our portable 12v cooler.

We do not have space for a generator so carry a small 4 phase 240v battery charger which we use when we are in a dock with shore power to condition the batteries.

  For what it is worth my list is pretty much the same except for the bilge pumps which I have never needed anyway - the only thing on this list that actually uses electricity is the laptop.

  Nav. LED use only 1.0 watt, cabin LED only 0.1 watt.

  Confusion comes from the mixture of units, bulbs etc. in watts, batteries in Amps

  To change watts to Amps just divide by 12 [ for 12 v system]  So a laptop of say 60 watts draws 5 amps each hour of use. So 1 hour use = 5amp/hour.  A [single bulb] LED cabin light will have to burn continuously for an almost incredible 120 hours to use a single Amp /hour !

There are very low energy alternatives to many things - hand pumps / wind scoops / wind vanes / solar fans / hand GPS / LED etc. The real users are , cooling,  laptop, fixed nav. system, steering.

On my boat I managed for years just by bringing a not-too-heavy battery ashore to charge - it would allow a week's cruise if the nav. lights were only used for 2 nights. No LEDs or laptops back then !

Now I have a 40 watt solar panel and 80 Ah battery and I had no shortage of power last summer cruising for several weeks. 

On my tiki 46 my current setup is 4x80w panels and a 400 w airx wind gen charging 750ah of deep cycle batteries. I have led cabin lights throughout but regular bulbs for nav lights, 12v fridge, 1000w inverter and the usual sailing instruments with a garmin autopilot with jefa rotary drive. The fridge is turned off at night and the Inverer runs for around 1-2 hours a day to charge laptops and other gadgets. I have a few 2w USB charging sockets installed for iPads etc.
I am finding in real world tests that my solve and wind is only just sufficient to keep the batteries between 50-100% charged and we are not extravagant with power usage. If the sun shines every day and it's windy then we are good however you can only really count on full solar chrge for around 6-8 hours per day. It should also be noted that ANY shade at all on the panels reduces the output considerably. My 240w of panels gives me an average of 10amps and I rarely get the theoretical 20 amps. So on a good sunny day the panels give me around 80 amp, just enough if I don't run the autopilot.
I am looking at installing an additional 200w of panels so as to keep my batteries at 80-100% charge and I think a second wind gen will be added at some point in the future.

On passage from brazil to Tobago whilst running the autopilot for severL days the batteries get seriously depleted and therefore the life( or charge cycles) is considerably shortened.

Also you only need a few days without sun or wind and the batteries are dead.

Don't even think of using automotive batteries as you'll kill them in no time. Good deep cycle batteries are the only way to go, and you must look after them.

Batteries and charging systems are a complex system and need designing properly or you'll be changing batteries frequently and they aren't cheap. My 750 ah bank cost well over 1000gbp and that doesn't include the heavy duty cables..

Look at installing 24v panels with an mppt controller and not a cheaper pwm controller as this is more efficient than using 12v ( really18v) as the mppt controller converts the excess voltage into amps instead of "wasting" the extra 6volts. This is a simplistic description but I'm sure a bit of googling will explain it in more technical detail.

Cheers

Marty

Robert you are right. But Paul lives in Australia...good solar cover. And his motor isn't eletric start. My Tiki have one batery 70A and 50W solar panel. But he stay stoped in sun almost all time. When I comes to sail, have fully charge always. I have:

3 cabin ligths (one led, 2 alogen)

Navigation mast ligths in leds

GPS chart plotter 421s garmin

Radio VHF/AIS standard horizon

st 1000 raymarine

1 jabsco water pressure pump 2.9

My maximun cruizing time was 8 day with 4 people, and never lacked  power. 

Robert Sheridan said:

It depends on where you are sailing: our solar panels work much better in the Med than in the UK.  We have 2 110 hour batteries, 4 ageing solar panels and a small wind generator.  With this set up we run all the things you list with the exception of bilge pumps and fans as we have neither but we do have more LED lights than you.  What we can not run unless it is strong sunlight and windy is our portable 12v cooler.

We do not have space for a generator so carry a small 4 phase 240v battery charger which we use when we are in a dock with shore power to condition the batteries.

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