Shore and Solar Power Schematic

[MadMango]

Anyone care to give me a sanity check on this schematic? This is for a camping trailer I'm building. I want the ability to connect to shore power when it's available, and also run on solar when it's not. I also just realized that the polarities are swapped on the output of the charge controller.

"Art without engineering is dreaming; Engineering without art is calculating."

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[MintJulep]

Nothing that prevents simultaneous battery charging from solar and shore power. Except you remembering to switch the switch.

You need a breaker at the shore power input.

30 amp breaker for 200 W of solar panel? Doesn't seem right.

I would want a way to charge battery from shore power and use 120 VAC simultaneously without the 12 VDC to 120 VAC inverter. You don't have that.

If batteries are discharged and you try to run your 12 volt loads while charging from shore power you will probably pop the output of the battery charger.

No safety ground (green wire) on your 120 VAC circuits.

 

[MadMango]

Thank you for the comments.

Nothing that prevents simultaneous battery charging from solar and shore power. Except you remembering to switch the switch.
Both the charge controller and battery charger are supposedly "smart" with auto shut-off features. I can see where another cut-off switch between the charger controller and battery charger would be nice. I'm not sure about doing this automatically.

30 amp breaker for 200 W of solar panel? Doesn't seem right.
Each panel's output on a sunny FL day was measured at 23.6V. So taking 100W / 20V = 5A per panel.

I would want a way to charge battery from shore power and use 120 VAC simultaneously without the 12 VDC to 120 VAC inverter. You don't have that.
I'll think on that.

If batteries are discharged and you try to run your 12 volt loads while charging from shore power you will probably pop the output of the battery charger.
Did not consider this.

"Art without engineering is dreaming; Engineering without art is calculating."

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[MintJulep]

Both the charge controller and battery charger are supposedly "smart" with auto shut-off features.

Still, allowing two smart chargers to pump electrons into dumb batteries at the same time could have unanticipated consequences. Like exploding batteries.

Doubtful that either charger manufacturer anticipated being connected in parallel with another charger.

 

[itsmoked]

1800W / 12Vdc = 150Amps.

Your inverter needs at least 150A of 12V power to reach its rating. Of course that means you also need
1/0AWG (called "one ought") sized cable (that's rated 75C or hotter) to support that.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

You can get probably get charge controllers that can be paralleled. If not you put in a
normally-closed double-pole relay that is run by shore power and disconnects the output
of the charge controller the moment you plug in the shore power.

You need to fuse or better yet breaker the 12VDC distribution. I suggest you go to a marine chandlery
such as West Marine and get an appropriate breakered distribution panel.

West Marine Breaker Panel Search

I didn't 'focus' the search since there are a lot of things here you should be considering. Large
inline breakers to protect the 1/0AWG cable. Possibly an AC panel. Metered panels that help you
recognize big loads and at-a-glance battery states, etc.

I highly recommend you go to this page:
Advisor Articles
and scroll down to the Electrical Section and do some reading. Your trailer almost
exactly matches a boat in its electrical properties. You can probably skip Under Water
Lights unless you have exotic trailering plans. Same for navigation lights.

Here's one of those links you'll find useful:
[URL unfurl="true"]http://www.westmarine.com/WestAdvisor/Marine-Wire-Size-And-Ampacity[/url]

I wouldn't doubt West Marine has everything you need for what you describe in your sketch above,
and people who can advise about the ability to connect their solar charge controllers to shore chargers etc.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[JohnRBaker]

While you're wiring up your camping trailer, you might want to consider adding some built-in 5 V USB power ports as they'll come in handy for charging cell phones/tablets/cameras/etc without wasting a valuable 120 V outlet.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[MadMango]

Keith,
Thanks so much for the research on the marine electrical components and sites. I'll check them out.

John,
Yes, I plan on using some of those wall outlets that have the normal plug and USB ports. In my schematic those are the 12VDC Ports.

"Art without engineering is dreaming; Engineering without art is calculating."

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[JohnRBaker]

But keep in mind that the normal USB power voltage is 5 VDC.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[GregLocock]

Your solar/battery size/inverter size is unbalanced. Pulling 1800W from 2x35 Ah 12V batteries is going to kill them in minutes, and they won't last many cycles of that.

A PWM solar controller is about 30% less efficient than an MPPT one. Basically your PWM controller wastes most of the voltage in excess of what the battery sees, whereas a decent controller will downconvert the voltage at which the solar panel is producing the most power (say 80% of open circuit) to whatever your battery needs.

I generally try not to discharge my batteries at more than C5, and also try (rather less successfully) to limit depth of discharge to 50%. That is, If had 2 35Ah batteries in parallel I'd pull 14 A in total for two and a half hours, from fully charged.



Cheers

Greg Locock


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[LittleInch]

Why don't you just look at a UPS? A simple ready made packaged supply. Many will allow you to take off 12V as well as give you the 110 or 220V supplies or exist as a unit and you add as many batteries as you want or could locate in a different place than the control unit. I suspect many now will also give you a regulated 5V USB power socket as well.

They have inbuilt chargers and auto switchover so you only need one set of 110V sockets, not two, it's all certified not to blow up or catch fire (kind of important in your wooden trailer...), you can get an efficient 110V convertor for your solar panels as an alternative feed into the UPS.

Your batteries actually look a bit weedy to me for the power coming from the solar panels. Battery charging for a long life for that size is probably no more than 2-3A max per battery and often lower.

This is where your UPS comes in handy as the incoming 110V ( from shore or solar) will either charge or use the battery power to give you 110V to run your systems.

I also agree that 1800W for your 110V invertor looks too big for the battery supplies you have. something will end up running very hot very quickly.

In case you weren't aware batteries for this type of use are termed "deep draw" or "deep cycle" and even then you are best limited to 30-40% charge.. Apologies if you already know this.

https://en.wikipedia.org/wiki/Deep_cycle_battery

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[MadMango]

Thanks Greg and LittleInch,
I have a lot of thinking to do. I'm starting to see how out of whack my system is. Currently I charge a 19Ah battery bank from one of my solar panels, and it runs two 12VDC fans and an LED task light perfectly fine for a weekend or so of camping. Additional task and area lights are the inflatable solar powered type, and they work just fine for our style of camping. I was just looking to "up" the overhead by running my other solar panel and going to bigger batteries in the off chance that I wanted to drag the laptop out to entertain my 4 year old when the sun goes down.

In the past, when shore power was available, it was as simple as plugging in a power strip to run whatever else was needed. I was looking for a method to combine to two systems.

"Art without engineering is dreaming; Engineering without art is calculating."

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[itsmoked]

"when whore power was available..."

Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

You should probably go with something like a 300W inverter. What really do you need it for?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IRstuff]

A lot of wear and tear on batteries come from high current discharge and/or charge. Also, apparent ampacity is likewise degraded by high current discharge. A typical rule of thumb is that discharge in amps be less to one tenth of the ampacity value, which in your case, would be 7 amps, or less than 84W

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[MadMango]

Keith,
Like I said, just a few fans, an LED light or two, and ability to charge a laptop. I was planing to use an 1800W simply because that's what I have collecting dust in storage.

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[TheTick]

I love that you call it "shore power".

 

[LittleInch]

I definitely preferred "whore power". Now sadly corrected by mango. ...

You confused us all by the 1800 W unit. My experience of these is that the cooling fans and other losses are significant at low power. Far better to get one sized for your duty. Your 1800 W unit could eat 5 to 10A before you even start to use any current on the output

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[MadMango]

Revised schematic, pulling back and trying to simplify things.

"Art without engineering is dreaming; Engineering without art is calculating."

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[LittleInch]

Why not just power the 110v battery charger of the 110v supply? Why have charger OR 110v fpower . Why not have both? Ditch the 1800w invertor and put in something smaller?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.