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Go Back   SailNet Community > Out There > Cruising & Liveaboard Forum > Solar power ~ no more running the engine
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Topic Review (Newest First)
08-11-2012 07:30 PM
davidpm
Re: Solar power ~ no more running the engine

Quote:
Originally Posted by paintpollz View Post
Thanks for the response BLjones.

When I get my first boat, hopefully within 5 years, I'll be a weekender and daysailor.
Five years!!!!
In five years we will probably have 100 amp batteries the size of a coke can and solar panel paint.

Everyone and their nephew is working on battery and solar tech.

Five years!!!!
08-11-2012 10:51 AM
foggysail
Re: Solar power ~ no more running the engine

Quote:
Originally Posted by hellosailor View Post
You got seduced by Ohm's Flaw. ;-)
That was so bad---- ugh!
08-11-2012 10:32 AM
hellosailor
Re: Solar power ~ no more running the engine

You got seduced by Ohm's Flaw. ;-)
08-11-2012 10:25 AM
foggysail
Re: Solar power ~ no more running the engine

Quote:
Originally Posted by hellosailor View Post
"I wanted only 30 amperes to be displayed so I installed a divider across the shunt's output terminals"

foggy, I'm not quite waht you've done but can tell you this is NOT THE WAY TO DO IT.

The way meters and shunts are set up, it doesn't matter what range you want to read. All that matters is that the mv-per-display has been matched between them, and that you don't exceed the maximum amperage that the shunt can carry. Whether you want to read 10 amps, 25 amps, or 50 amps...if you have a meter and 50a shunt, they are set up the same way regardless.

I would strongly suggest that what you've done now is simply to distort all the readings. And, perhaps, that's related to the shunt overheating as well.

Some of the bargain stuff from China, which is SO attractively priced, almost scares me. The shunts are visibly different from the pricey domestic ones, and the all-in-one digital meter displays seem to vary quite widely in quality. (I've got two that never agree, even though they are supposedly calibrated and way exceed their display accuracy.)

50A shunt, 50A meter, put it back to the original configuration and it will read 30A scales just fine. Really.

GEEZ, I don't know what the heck I was thinking! Did this exercise late at night but thats a poor excuse. I scaled the 75mv for 30 amperes completely ignoring that the voltage drop of 75 mv depends on the current flow I through a resistor of value R. I just removed the divider, and you are embarrassingly correct, it will read 30 amperes if the shunt is correctly calibrated and of course, current flow is 30 amperes. Thanks for pointing out my screw up, I just deleted that mess from the previous post.


As to the stuff for China-- you pays you money, you takes you chance. Something as simple as a meter/shunt in a non critical application is fine.

Foggy
08-10-2012 07:54 PM
hellosailor
Re: Solar power ~ no more running the engine

"I wanted only 30 amperes to be displayed so I installed a divider across the shunt's output terminals"

foggy, I'm not quite waht you've done but can tell you this is NOT THE WAY TO DO IT.

The way meters and shunts are set up, it doesn't matter what range you want to read. All that matters is that the mv-per-display has been matched between them, and that you don't exceed the maximum amperage that the shunt can carry. Whether you want to read 10 amps, 25 amps, or 50 amps...if you have a meter and 50a shunt, they are set up the same way regardless.

I would strongly suggest that what you've done now is simply to distort all the readings. And, perhaps, that's related to the shunt overheating as well.

Some of the bargain stuff from China, which is SO attractively priced, almost scares me. The shunts are visibly different from the pricey domestic ones, and the all-in-one digital meter displays seem to vary quite widely in quality. (I've got two that never agree, even though they are supposedly calibrated and way exceed their display accuracy.)

50A shunt, 50A meter, put it back to the original configuration and it will read 30A scales just fine. Really.
08-10-2012 07:38 PM
foggysail
Re: Solar power ~ no more running the engine

Getting close! Tomorrow I should have my system up! I mentioned earlier that I purchased the Prostar 30 without the pricey meter. I just finished building a meter assembly that I stuffed into a plastic weather proof electrical box. I cut the blank cover to mount the meter which was calibrated to a 75mv shunt for 50 amperes. (edited--thanks to Hellosailor) I mounted the shunt on the rear of the box.

Finally I installed a jack that accommodates a 5.6 volt dc output from a transformer that will power the meter with about 5 vdc rather than the 12vdc that the meter is rated for. I found that the meter gets hot indicating the thing must have a zener diode in it for regulating. The dc output from the meter is......well it is really full wave rectified voltage with no filtering. Who cares if it works.

If anybody considers building their own metering unit, be careful to use a separate power supply...completely isolated from the supply whose current is being metered. Alsom the measuring is done on the return leg of the solar output. Enough of the simple basics.

Because the shunt can dissipate upwards to 2 watts, I have it mounted such that air can pass through the shunt for cooling. The box/shunt combo will mount tomorrow on plastic stand offs so the box will be about 3/4" off the wall giving clearance for the shunt proper.

Getting excited! We are taking next week off so it will be a good time for testing. My luck or lack of will probably see nothing but clouds and rain. More on that later. Another awe shucks! If I add another pair of panels, I will most likely exceed the rating for the Prostar. Time will tell. I have not seen any more of these panels on Amazon lately.

CRRHODES--- You must have installed your panels sometime ago, I see that your setup cost about $5K. That is way beyond what I can afford at present. If these cheapo panels were not available, I would have no solar.

Your experience provides valuable insight on what to expect. Certainly I expect to run my genny when on anchor, I just don't want to run it to charge batteries unless I have to. I want my genny to provide energy for hot water, stove.... all the basics. OH, it will have to recharge my 24vdc battery bank, I can live with that.

More over the weekend!!!

Foggy
08-03-2012 10:49 AM
CRHODES
Re: Solar power ~ no more running the engine

Hi, I put in a system on my houseboat with 4 solar panels/6 batteries and the cost ran about $5000 US, it generates about 2.2 KW per day on a good day, which is enough to run the refrigerator and a few other things and the boat lights and equipment.

But the reality is, it can not do that consistently, I can go 3 days or so out on the hook with no generator but after that it becomes a game of how much sun do I get.

It would be possible if I had more solar panels and batteries to do more but at the moment till the costs on solar panels comes down a lot more it is not cost effective IMO.

Hope that helps happy to share more details if your interested.
07-25-2012 06:15 PM
DavidB.UK
Re: Solar power ~ no more running the engine

Hi everybody,

Thought this might be of interest and oddly relevant to this thread...
07-25-2012 04:44 PM
noelex77
Re: Solar power ~ no more running the engine

Quote:
Originally Posted by foggysail View Post
Noelex---

Sometimes you guys remind me of WIFEY!!!!
Well I am glad we are not sharing accommodation, otherwise I would be nervous

I think you made the right decision.
07-25-2012 04:12 PM
foggysail
Re: Solar power ~ no more running the engine

Noelex---

Sometimes you guys remind me of WIFEY!!!! WHAT DID YOU DO THAT FOR?????????

Yes, I did think about the 30 ampere unit, ruled it out because the cost was doubled at least where I looked previously.

I purchased the 15 ampere unit this morning from SolarHome.org. After reading your post and weighing how I made the trade off whereby I selected the 15 ampere unit, I rechecked the price of the 30 ampere unit at SolarHome where I placed my order this morning. Cost differences was $34.50! I quickly called the company who was wrapping my order for shipment and asked to upgrade to the 30.

Guess it was a wise move for the cost difference. What motivated me earlier to go with a 15 ampere controller was my thought that we most likely will rarely see enough sun to get the full 8 amperes output, If we did, weeell, so a couple of mosfets/diodes would just have to run hotter. But after reading your post I again thought, suppose I add another panel next year, then what?

Thanks Noel for posting a concern and yes, the voltage is 12 not 24.

Foggy
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