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Old 20-01-2017, 20:41   #16
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Re: Opinions on solar power

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Originally Posted by onebigadventure View Post
I have been reading that people use these 6v deep cycle. What is the difference between that and 12v? I was also looking into golf cart batteries i hear work well.
The 6volt batteries are golf car batteries. And yes they work well imo more bang.for your buck.
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Old 20-01-2017, 20:55   #17
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Re: Opinions on solar power

Whats your power budget in terms of Amp or Watt hours?

Once you know that then you can size house battery and then charging requirement.
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Old 20-01-2017, 20:58   #18
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Re: Opinions on solar power

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The 6volt batteries are golf car batteries. And yes they work well imo more bang.for your buck.
Ok so i was just looking up prices. The 12v is around 125 and the 6v are 109 for Duracell. That was a quick google search. Im assuming i would need more than 4 for house and a 12v for engine? I don't think that would save too much money as opposed to 12v...
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Old 20-01-2017, 21:12   #19
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Re: Opinions on solar power

We have two 120 watt solar panels and an mppt controller. No generator. Have led interior and nav lighting, iceer refrigeration and freezer compartments (draw 5 amps when cool kicks on), 9 in Zeus 2 plotter and 4 g radar, ais, xm radio, vhf, and a DC watermaker. Three 105 amp batteries. We did three months on the boat last year (Texas to Bahamas and back) and only had a battery drain problem once when I ran watermaker on cloudy day.

No computer. Carried a Honda 2000 that I ran a total of four hours. When motoring, the two 9.9 hp outboards put out some power. But for the two months we were in Bahamas we used less than 20 gal gasoline, so not much charging to be had.

Long overnight sails with all instruments, vhf, ais, radar and m radio running was the worse consumption. The watermaker drew 8 amps, but only ran it in mid day sun when there was extra solar juice.
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Old 20-01-2017, 21:57   #20
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Re: Opinions on solar power

Quote:
Originally Posted by onebigadventure View Post
Ok so i was just looking up prices. The 12v is around 125 and the 6v are 109 for Duracell. That was a quick google search. Im assuming i would need more than 4 for house and a 12v for engine? I don't think that would save too much money as opposed to 12v...
I would be willing to bet good money that the 12volt battery is not a deep cycle battery and wohld likely fail in deep cycle service in under a year. The duracell gc2batteries are true deep cycle batteries made by east penn . They are 85 at sams club here. What is the 20 hour ah rating on the 12 volt battery? If it doesnt have an actual ah rate its not a true deep cycle.
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Old 20-01-2017, 22:04   #21
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Re: Opinions on solar power

Afor your boat for now a pair of 6 volt batts and a s ok ngle isolated 12volt start battery you will be ok do your power budget and go from there.
Ran dads 42 ftter with a pair of.trojan 6v house bank and 2 100 watt rigid mono panels
Omplete with 12volt holding plate refer system 8 month out of the year with no outside charging source. Here at 48 north there is to little sunlight time each day in the winter.
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Old 20-01-2017, 22:24   #22
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Re: Opinions on solar power

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Originally Posted by onebigadventure View Post
I was thinking 240w should be sufficient. Appreciate any advice in advance!
240W in ideal conditions would give you a maximun charging of about 14 amps per hour. Anything less than ideal meaning not mid-day, cloudy, bit of shading, not good panel orientation, cables too thin, controller not so good, corrosion, batteries bit tired, etc., and you will get less.

If your refrigeration machinery and the actual insulation are not very good (old boats typically have very poor wet soaked foam insulation around the box) the fridge may have a surprisingly high draw, even more than 100amps per 24 hour, especially after you filled it with warm produce after a shopping trip. If ok you might have about 50 amps per 24 hours draw.

Laptops (especially), tablets and phones require a lot of charging. You should really search this topic more and do an energy budget like suggested previously.

I second the Honda 2000 / 20EU. Good addition to solar. Some folks say a wind generator is useful in the caribbean region, might keep your bats charged during the night also

Just search (Google "cruisersforum xxxxxxxx...") and find lots of info.

Cheers
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Old 21-01-2017, 00:31   #23
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Re: Opinions on solar power

It's my turn to be the stickler for using the correct units when it comes to amps, and amp hours. Here goes:

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Originally Posted by ErikFinn View Post
240W in ideal conditions would give you a maximun charging of about 14 amps per hour.
Make that "14 amps".

Quote:
Anything less than ideal meaning not mid-day, cloudy, bit of shading, not good panel orientation, cables too thin, controller not so good, corrosion, batteries bit tired, etc., and you will get less.

If your refrigeration machinery and the actual insulation are not very good (old boats typically have very poor wet soaked foam insulation around the box) the fridge may have a surprisingly high draw, even more than 100amps per 24 hour,
Make that "100 Ah (Amp hours) in 24 hours".

Quote:
especially after you filled it with warm produce after a shopping trip. If ok you might have about 50 amps per 24 hours draw.
Make that "50 Ah in 24 hours".

Quote:
Laptops (especially), tablets and phones require a lot of charging. You should really search this topic more and do an energy budget like suggested previously.

I second the Honda 2000 / 20EU. Good addition to solar. Some folks say a wind generator is useful in the caribbean region, might keep your bats charged during the night also

Just search (Google "cruisersforum xxxxxxxx...") and find lots of info.

Cheers
Erik, your data is good, but the your terminology leads to confusion. You're not the only one who gets this incorrect, and we've had many heated arguments here on the subject. Some people disagree with me on this, but they're wrong.
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Old 21-01-2017, 01:08   #24
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Re: Opinions on solar power

and I thought I made a special effort to make it exceptionally clear..
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Old 21-01-2017, 01:31   #25
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Re: Opinions on solar power

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Originally Posted by ErikFinn View Post
and I thought I made a special effort to make it exceptionally clear..
And this is exactly the problem that Paul (and a lot of others) are trying to address. Folks really need to master the simple units involved with DC electricity if they want to discourse meaningfully about it.

It isn't all that hard, and StuM has posted good summaries of the terms and their meanings. If we all read and understood and then used the new knowledge, life would be better and we could stop all these posts from littering the internet.

It's important... not nitpickery.

Jim
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Old 21-01-2017, 04:41   #26
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Re: Opinions on solar power

Jim and Paul.

Energy is the amount of work you need to do to accomplish some task. If you lift one case of beer off the dinghy onto the boat, you've done some work. If you lift a second case of beer, now you've done twice as much work. Whether you lifted them both at the same time or one after the other doesn't matter, it's the same amount of work, aka energy, in total. 2 cases worth.

Power is how much work you can do in a certain amount time. I'm a wimp and can only lift one case of beer at a time. My buddy can lift two. He's twice as powerful as me. If hoisting a load of beer onto the mothership takes 10 seconds, my power output is 1case/10seconds. My buddy's is 2cases/10seconds.

To be fair, my buddy and I will each unload half the beer. In total, when we are done loading up, we'll each have done the same amount of work (aka, expend the same amount of energy) but since my buddy is twice as powerful as me, he'll be finished with his share of the work in half the time.

Additionally, if you want to know how much work I can do in 60 seconds, multiply my power output by 60 seconds. (1 case / 10 seconds)*60 seconds = 6 cases loaded on deck. Power, multiplied by time, equals energy. Mmmmmm beer.

For a given voltage,

the Amp is a measure of power.

and

The Amp hour (Ah, amp * hour) is a measure of energy.


Power, multiplied by time, equals energy.

Example: Your alternator may be really powerful and put out 200 amps. Run it for a few seconds and you haven't stored much energy in your batteries (200 amps *.001 hours = 0.2 amp hours), you won't be able to do much work with that! Run it for an hour and you'll have 200 amp hours of energy, nice, time to chill the beer.
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Old 21-01-2017, 05:33   #27
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Re: Opinions on solar power

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Originally Posted by chris95040 View Post

...

For a given voltage,

the Amp is a measure of power.

and

The Amp hour (Ah, amp * hour) is a measure of energy.

Power, multiplied by time, equals energy.

Example: Your alternator may be really powerful and put out 200 amps. Run it for a few seconds and you haven't stored much energy in your batteries (200 amps *.001 hours = 0.2 amp hours), you won't be able to do much work with that! Run it for an hour and you'll have 200 amp hours of energy, nice, time to chill the beer.
Nice summary

Just for completeness:

You can also delete "For a given Voltage" and replace the word Amp with Watt above. (Which is useful when you are looking at solar panels and energy consumers which are frequently rated in Watts.)
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Old 21-01-2017, 07:31   #28
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Re: Opinions on solar power

We have Deka 12 volt 105 amp-hr agm batteries. They are made by east Penn. Two house, one motor. The first set lasted 11 years before one went out, and I replaced all three. With such good service, went right back with Deka agm. I think they were about $200 each. Don't skimp on the batteries or the solar controller. My blue sky mppt controller is very efficient as well as nice on the battery bank being three phase temp compensated.
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Old 21-01-2017, 07:48   #29
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Re: Opinions on solar power

From memory, big power hogs on our boat are the fresh water pump at 9 amps, although it runs only short periods. Next the refrigeration, which is 5 amps when the cooling cycle kicks on. The watermaker is 8 amps. Night sailing on passage with the chartplotter, radar, ais, vhf, nav lights and xm radio (music) is around 8 amps. So if you do that for ten hours, it's a big draw on a 300 amp-hr bank. You can switch back and forth on radar transmit vs standby to help that, but my 4g radar is pretty miserly.

Sitting at anchor, our overnight use is usually only about 25 amp hours. Interior and anchor lighting, refrigeration, water pump to wash dishes and showers, portable DVD player. On sunny day the solar panels have batteries back up to 100% by noon. Then we run watermaker in full sun period and the panels provide for that power usage.
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Old 21-01-2017, 09:25   #30
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Re: Opinions on solar power

Can't imagine 240 watts woukd be enough for refrigerator and computers. They are energy hogs. posters who said do a budget are correct.

Also, don't count on getting 240 watts out of the panel(s). Very rare to get full rated output.

With 720 watts I tend to get between 180 and 200 amphours a day in the Caribbean this time of year. Could get more if I tilted panels to follow the sun but in the real world that just doesn't seem to happen.

Computers and refrigerate can eat half of my output.

Bill
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