Challenges with Solar on boats

[john61ct]

With shipping, savings is under $100 vs known good US sources.

Lots of such "factory identical" turn out to substitute inferior parts, are QA rejects, then warranty issues...

Recommend not worth the additional risk.

[a64pilot]

I spent a year stationed in Korea, you can get nearly exact copies of anything there, just take them a picture and pick up the leather coat in a few days, brass beds, anything.
But we called it the land of not quite right, as all the knock off stuff was close, but just not quite right, although I still have a few Rolexes that still work and they look nearly identical, until you pick one up, just no weight to a Korean copy, and of course internally it's not Rolex, not nearly so.

Just cause something looks similar, does not mean that it is.
I don't think Outback manufactures in China, do they?

[jheldatksuedu]

Originally Posted by ramblinrod

First of all, needlessly complicated for no benefit.

Second, it won't work.

The high impedance of the 3 fully charged unloaded batteries in series, would restrict the current from the charger supplying the loaded battery circuit as needed.

Third, not marine standards compliant.

The DC distribution and charging system must be connected to one system ground. A wiring fault in the system you propose could result in a whole lot of hurt.

Per ABYC (from memory, I'm having trouble finding the relevant section at the moment), if a series bank is tapped as you indicate, there has to be a method to equally load the other batteries in series.

I'm not needlessly complicating it.

I have 7 solar panels (3 large and 4 small) and 5 batteries (4 large and one starting), everything on the boat is 12 volts,

I need to get solar panel controllers and put my system together, so I looking for alternatives.

If I hook up the 4 batteries in series I can charge them all with one solar panel set up and one controller.

In order to use the 12 volts I can only hook up to the lowest battery in the series connection. I could get 24, 36 ,or 48 volts if I wanted but I don't want that. I would like to be able to use and discharge the 3 other batteries.

I could use and discharge the 3 other batteries if I would connect to both positive and negative on that battery, but then the system hooked up to that would have a ground voltage that is not the same as the lowest voltage terminal on the lowest battery in the 4 battery series connection, so I would need to be careful to not connect those grounds together.

I could do this by having the 4 batteries and the solar panel system not connected tp the boat ground, (electrically floating).

I then could connect to any of the 4 batteries, as long as I only connect to both positive and negative of the that battery and use the power out of that battery. The negative of that battery could be connected to the boat ground, that would effectively connect the solar and battery system to a ground and not be totally floating, but the lowest voltage in the battery and solar system might not be at boat ground, not a problem, but something to be conscious about.

In order to equally discharge all 4 batteries it would be nice to have an automatic switch to do this battery connection change, and also have a small battery (such as a motorcycle battery) to supply power to whatever is hooked up and using power during the instant that the batteries are being switched.

I'm new at this, boat solar power systems, but not new at electronics and such, I taught university electrical engineering. It's quite common for inventors with new ideas to be laughed at by people that can't understand what they are doing.

This system can simplify the solar charging apparatus needed on the boat. It just needs a complicated switch to do that and that switch should be much cheaper than 3 more solar controllers. I'm just trying to save money. Also that switch is probably much more reliable than a solar controller. It is nice to be able to increase reliability and save money at the same time.

I hope that I have put this is complete and simple enough terms that you can understand my proposal. So please tell me why this would not work. I know it would, it might not be smart for some reason I don't understand, that's why I'm on here to get other opinions, and learn.

If you have 4 batteries in series the voltage is the sum of the 4, say 3 at 12 and one at 11, that is 47. if you have that connected to a solar system supplying 48, current will flow and it will try to charge all the batteries, as long as it does no damage to the 3 fully charged batteries it will charge the discharged one. The idea is not to have 3 fully charged and one discharged, the switching system should give you 4 rather equally discharged batteries. and they all will charge, that's what we want. If the current is large enough with the 3 full batteries and one discharged it could boil the 3 and do damage, but the idea is to not have that situation. The ideal automatic switch would switch to the battery with the highest voltage.

[newhaul]

Originally Posted by jheldatksuedu

I'm not needlessly complicating it.

I have 7 solar panels (3 large and 4 small) and 5 batteries (4 large and one starting), everything on the boat is 12 volts,

I need to get solar panel controllers and put my system together, so I looking for alternatives.

If I hook up the 4 batteries in series I can charge them all with one solar panel set up and one controller.

In order to use the 12 volts I can only hook up to the lowest battery in the series connection. I could get 24, 36 ,or 48 volts if I wanted but I don't want that. I would like to be able to use and discharge the 3 other batteries.

I could use and discharge the 3 other batteries if I would connect to both positive and negative on that battery, but then the system hooked up to that would have a ground voltage that is not the same as the lowest voltage terminal on the lowest battery in the 4 battery series connection, so I would need to be careful to not connect those grounds together.

I could do this by having the 4 batteries and the solar panel system not connected tp the boat ground, (electrically floating).

I then could connect to any of the 4 batteries, as long as I only connect to both positive and negative of the that battery and use the power out of that battery. The negative of that battery could be connected to the boat ground, that would effectively connect the solar and battery system to a ground and not be totally floating, but the lowest voltage in that system might not be at boat ground, not a problem, but something to be conscious about.

In order to equally discharge all 4 batteries it would be nice to have an automatic switch to do this battery connection change, and also have a small battery (such as a motorcycle battery) to supply power to whatever is hooked up and using power during the instant that the batteries are being switched.

I'm new at this, boat solar power systems, but not new at electronics and such, I taught university electrical engineering. It's quite common for inventors with new ideas to be laughed at by people that can't understand what they are doing.

This system can simplify the solar charging apparatus needed on the boat. It just needs a complicated switch to do that and that switch should be much cheaper than 3 more solar controllers. I'm just trying to save money. Also that switch is probably much more reliable than a solar controller. It is nice to be able to increase reliability and save money at the same time.

I hope that I have put this is complete and simple enough terms that you can understand my proposal. So please tell me why this would not work. I know it would, it might not be smart for some reason I don't understand, that's why I'm on here to get other opinions, and learn.

What you propose makes no sense from a mechanical engineering standpoint. Why do you wish to connect the batteries in series ( thereby increasing the voltage from 12 volts to whatever voltage) imho this is the setup I would recomend. Hook batteries in parallel thereby increasing the ah without changing the voltage. Secondly running your solar array through an appropriately sized mppt controller to charge the bank. Why make it overly complicated. (KISS)

[jheldatksuedu]

Originally Posted by newhaul

What you propose makes no sense from a mechanical engineering standpoint. Why do you wish to connect the batteries in series ( thereby increasing the voltage from 12 volts to whatever voltage) imho this is the setup I would recomend. Hook batteries in parallel thereby increasing the ah without changing the voltage. Secondly running your solar array through an appropriately sized mppt controller to charge the bank. Why make it overly complicated. (KISS)

On the surface I have to agree, I'm trying to remember what got me to wanting to hook the batteries in series, it had something to do with charging efficiency of the controller and voltage I think. It was back when I was considering parallel vs series panel connections and shading problems. I'll have to go back and figure that out. It seems I decided I would need to have 4 controllers each charging a separate battery

My degree is in ME and I taught that for most of my career.

[Kenomac]

Originally Posted by john61ct

With shipping, savings is under $100 vs known good US sources.

Lots of such "factory identical" turn out to substitute inferior parts, are QA rejects, then warranty issues...

Recommend not worth the additional risk.

No kidding... I recently purchased what was supposed to be an Apple OEM charger for my Macbook pro on eBay for $29 instead of $57 at Bestbuy, has the apple logo and looks genuine. I had two of them go bad within two months. Only the OEM charger purchased from Bestbuy is still working. And now the cost has increased to $79.

Lots of fakes (Chinese counterfeits) out there.

[Leo Ticheli]

I suppose anything, no matter how uncomplicated, can be done incorrectly, thus things like, "Front toward enemy," or, "Caution: contents hot."
I am not an engineer, but building the stainless steel frame, mounting the solar panels and controller, and doing the electrical was quite easy. I've got three panels for a total of 416w and have never had a problem of lack of power. I am thinking of replacing my one 100w panel and adding an additional 158w panel just for the hell of it.

It's not rocket science; if I can do it, anyone not institutionalized can do it.

Fair winds,
Leo

[john61ct]

Well many don't have the experience and/or lack confidence. Insulting them is not helpful

[Rorzech]

I like the idea of using bigger panels , the only down side is if you accidentally drop a d-ring or something hard, on one big panel, you loose a bigger portion of your system. I Still like the Idea of 2 450 W panels with two MPPT controllers.

[mitiempo]

Originally Posted by jheldatksuedu

I'm not needlessly complicating it.

I have 7 solar panels (3 large and 4 small) and 5 batteries (4 large and one starting), everything on the boat is 12 volts,

I need to get solar panel controllers and put my system together, so I looking for alternatives.

If I hook up the 4 batteries in series I can charge them all with one solar panel set up and one controller.

If you wire the batteries in parallel you can charge them with the solar array and one controller. You will not suffer the issues you get with shading series panels. What could be simpler?

[jheldatksuedu]

Originally Posted by newhaul

What you propose makes no sense from a mechanical engineering standpoint. Why do you wish to connect the batteries in series ( thereby increasing the voltage from 12 volts to whatever voltage) imho this is the setup I would recomend. Hook batteries in parallel thereby increasing the ah without changing the voltage. Secondly running your solar array through an appropriately sized mppt controller to charge the bank. Why make it overly complicated. (KISS)

I remember now why I wanted to go to higher voltage, it is efficiency, the loses in the wires are due to the current not the voltage, at higher voltage and reduced current you have much less loss. In this case the losses in the charging system could be 1/16 as much, a major improvement. It's I squared R. We are working with such small amounts of energy from a solar panel every improvement can be important.

[newhaul]

Originally Posted by jheldatksuedu

I remember now why I wanted to go to higher voltage, it is efficiency, the loses in the wires are due to the current not the voltage, at higher voltage and reduced current you have much less loss. In this case the losses in the charging system could be 1/16 as much, a major improvement. It's I squared R. We are working with such small amounts of energy from a solar panel every improvement can be important.

This is true for the runs from panels to controller however the runs from the controller to the battery that losses are minimal to virtually nonexistent.

[john61ct]

As long as controllers are mounted near the banks as they should be.

[Utahsailor]

In my 12V system of 840W Kyocera panels, dual Morningstar controllers and 10 Trojan T105s, I have to add water every week. Today I added nearly 1/3rd gallon after 1-1/2 weeks. This seems excessive and I notice that the Morningstar are putting more amps into the batteries at nearly full charge than the Balmar controller on the engine or the Xantrex when hooked to shore power. Does this seem excessive?

[atlantical]

I have two batteries, and one solar controller, so, my solar goes to battery one, only way I can charge both batteries at one time, is switch the main battery switch to both, what I may ad, is a switch splitting the cable from the solar, so with my battery switch off, I can chose what battery to charge, switch that switch from battery one, or battery two, and the main switch can be switched off, just now with that switched off, all i can charge is battery one. If I was to connect the positive from the solar to both batteries then I could never isolate them from each other.