Solar Panel demands - Page 3 - SailNet Community
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post #21 of 25 Old 02-23-2012 Thread Starter
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Yes the boat has an amp meter. I tried to isolate each potential draw on the system and then factor in maximum usage on a 24 hour day. So for instance on auto pilot if it is working hard it was 5 to 6 amps x 24 hours. My goal is to set the boat up for offshore / coastal cruising and not have a generator aboard.
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post #22 of 25 Old 02-23-2012
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Things like a frig and air conditioning draw a lot of power. You probably cannot realistically run an air conditioner off solar panels on a boat- not enough space to mount the solar panels and cost prohibative for panels and battery storage. As far as the frig- I think it would depend on what your have- you may benefit from replacing it to a lower energy use model. If you are going to do some heavy sailing- go with a wind vane instead of an auto pilot- no power use.
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post #23 of 25 Old 02-23-2012
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That depends

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Originally Posted by jkzdad View Post
Yes the boat has an amp meter. I tried to isolate each potential draw on the system and then factor in maximum usage on a 24 hour day. So for instance on auto pilot if it is working hard it was 5 to 6 amps x 24 hours. My goal is to set the boat up for offshore / coastal cruising and not have a generator aboard.
Several comments based on my experience since I went through a similar exercise myself.
1. You mention nav system taking a lot of juice in an earlier post. I assume you are referring to your autopilot, not to instruments? Really the big users are refrigeration, autopilot, and nav lights (already mentioned). If your autopilot is using 6 amps it is not actually turning 24 hours a day. It is the motor that uses the power, not the monitoring of course. You can try to estimate what percentage of the time it is actually motoring. IF it is 33% of time then we are looking at about 50 a/h a day.

2. You suggested 4 x 135 watt panels. That should be ample for your needs. We have 2 x 80 and a Air Machine wind generator and can sit in an anchorage for three weeks without a problem. Some caveats from my research (aren't there always caveats), there are two kinds of serious solar panels - monocrystalline and polycrystalline. Most of the ordinary panels for sale are the latter. This type is extremely susceptible to shadows. Even the shadow of the backstay can reduced output 50%. I looked very seriously for monocrystalline ones but they did not seem to come in the correct dimensions to meet my needs - I have my panels swing out from the lifelines to reduce shading.

3. Where you are cruising makes a big difference. In the Caribbean the sun is strong and the winds pretty constant so it pretty easy to be self-sufficient with renewables. If you are in New England it is not as easy of course.

Slighly off-topic, when say you want to go offshore -how far off are we talking? Electric autopilots are fine but you really, really need redundancy with them. It is very common to hear about people doing long passages having a problem and falling back on autopilot #2. If you are going to go very long distances (longer than to Caribbean) you might want to consider vane steering (and an autopilot for redundancy and use when you are motoring). This would save you another whack of power.

After the refit we have decided to sell Ainia. We want something smaller that would be could for the light summer winds of Lake Ontario, although we plan to spend at least a couple of winters in the Caribbean before heading north.
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post #24 of 25 Old 02-23-2012 Thread Starter
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Killarney Sailor thanks for your input. Our initial plan is to sail down to Mexico and keep the boat there 1 to 2 years and then depending on circumstances potentially go through the canal to Caribbean or take jump over to French Polynesia. Either way the idea is to be self sufficient using solar power and conservative energy usage to enjoy time on the boat. The way the Beneteau 46 is set up with the beamy aft cockpit we can have a tower built above our existing bimini top that could support and house 4 135watt panels with pretty good unobstructive positioning to the sun. That so far is the plan. Your comments are very useful and any other input appreciated
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post #25 of 25 Old 02-23-2012
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Originally Posted by jkzdad View Post
Thanks for the good ideas regarding the led lighting. Another big amp draw while cruising would be the nav system usage. I am Trying to plan for the days with the most energy draws. I think the need for some energy austerity on these big draw days is a big part of the answer. Thanks again

Bill
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Bill,

You'd be well served to get yourself a battery monitor. I see people spend way less than they should or way MORE than they should and a battery monitor would answer all your "load" questions so you can "accurately" size your system.

The Victron BMV-600 is about $180.00 and is money well spent if installed and set up correctly...

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