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thataway



Joined: 02 Nov 2003
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PostPosted: Sun Oct 30, 2016 10:44 pm    Post subject: Reply with quote

How many watts are your water heater elements? Most are 1200 watts for the standard heater. That's a lot of power....
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Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
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Sunbeam



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PostPosted: Mon Oct 31, 2016 11:00 am    Post subject: Reply with quote

I don't use the "load" setting, or have a water heater or any other official way to use otherwise wasted power (by which I mean afternoon when batteries are already back to 100%). But I do have ways of using it. This is when I charge things (computer, AA and AAA batts, tablet, phone, power tool batteries) and/or do things that use power that I might as well do at that time anyway.

Not that I don't charge and do things at night (definitely do, as a night owl), but it's just that I keep in mind when I do and don't have excess power. In a similar/opposite vein, if it's morning and I'm in the absorb stage, I won't likely choose that time to start charging big things (that would knock it out of absorb; sure it would go back later, IF the sun was still out, etc.)

This isn't to say I watch it like a hawk, or have to super-worry about it; but just that all else being equal, I'm there, I have the time, etc. --- I don't just *ignore* where things stand in the charging cycle.

That works well for me because water heating is a small part of my daily life (and I do it on the stove); whereas things like computers, tools, and AAA batts are more frequently used.

(The big draw, the refrigerator, just gets to do its thing.)
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Foggy



Joined: 01 Aug 2013
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PostPosted: Mon Oct 31, 2016 11:26 am    Post subject: Reply with quote

This wasted heat brings up another (missed, forgotten, not mentioned, probably
not believed) point about the difference(s) between PWM and MPPT charge
controllers (see UTube, my authoritative scientific source).

When battery charging is complete and the circuit is open (between the panels
and the charger), the PWM charger apparently dissipates the charge coming
from the panels as wasted heat. Probably not enough heat for a shower.
Makes sense as the panels don't know the circuit is open since it is in the
controller and the panel cells still have solar energy (perhaps) + amorphous or
poly crystalline or slim film silicone - everything a solar cell could want to do
its thing.

The more complex and efficient MPPT controller uses the energy from the panels
at open circuit time to convert this energy into useful amps (aka 'the boost', or
part of 'a boost'). Hence, part of the higher price tag. You get what you pay for;
no free lunch.

And on it goes...

Aye.

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Sunbeam



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PostPosted: Mon Oct 31, 2016 11:45 am    Post subject: Reply with quote

Maybe I should have added that I use an MPPT controller. I have never had a PWM controller, so can't comment on any differences beyond just what anyone can read in the manuals.

I can say that although there can be times when potential power is not used (say the batteries are at 100%, the refrigerator is off, and I'm not charging anything), and at those times the controller doesn't heat up, and I don't notice the panels getting any hotter than normal (of course black panels in the sun are always going to be hot).

The meter on my solar controller shows me the temperature of the controller and of the battery bank. The controller never heats up in any notable way. For the panels I'm just going by the fact that I handle them (when on land I sometimes move them or change the angle).

This is getting beyond my experiential knowledge and more into theory, but I remember reading something about how solar panels are not really "power providers" but instead provide current. Does that have something do do with it? For my uses they are the same (amps), but in the dark recesses of my mind there is something that says it matters in some way. Again, I only know how to wire them (avoid voltage drop, fuse properly, match volts in parallel and amps in series, etc.) and use them (set solar controller parameters, etc.); the electrical theory details are not all understood by me (current vs. power, etc.).
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Marco Flamingo



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PostPosted: Mon Oct 31, 2016 1:16 pm    Post subject: Reply with quote

thataway wrote:
How many watts are your water heater elements? Most are 1200 watts for the standard heater. That's a lot of power....


The smallest one that I have is 300W. I have another one somewhere that is 1,200, but it has two elements on a single fitting, so it can be wired for 600 or 1,200. The little one is 25 amps at full tilt and will boil a gallon of water in short order (so it would require a thermostat if in a small tank). The idea is that any excess solar, even if it only heats the water in a 40 gallon tank 20 degrees is "free energy" if the alternative is just shutting down the panels when the batteries are full.

I played with the smaller one a little for possible boat application on my 16. It got more complicated than what I need. I don't really need hot water on demand. My little solar panel (4W), when connected directly to the little element, only got water slowly luke warm, not worth messing with. If connected to my battery bank, it heated like crazy. I would need a thermostat. But the biggest worry was having an electrical drain that exceeded my alternator output. Losing juice even with the engine running makes me nervous, especially when my induction burner can heat the little amount of hot water that I need and stay within alternator production.

Mark
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Foggy



Joined: 01 Aug 2013
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PostPosted: Mon Oct 31, 2016 4:56 pm    Post subject: Reply with quote

Now here's something from Solbian (made in Italy):

http://www.solbian.eu/en/blog/solbian-allinone-to-see-at-mets-the-first-flexible-solar-panel-with-integrated--n29

72W panel (and smaller) with a MPPT controller built right into the panel.
Available at www.emarine.com and www.bruceschwab.com

Cool but red doesn't go with my stuff.

Aye.
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kaelc



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PostPosted: Sun Mar 14, 2021 12:33 pm    Post subject: Reply with quote

Would love to find out how your system preforms under real world testing. I just picked up a big old version of your freezer. When fishing using dual screens electric downriggers and radar I feel like we are taxing our battery/alternator combo. Be nice to have significant solar work confidence it will keep us topped up!
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