Challenges with Solar on boats

[john61ct]

Originally Posted by jheldatksuedu

I'm asking for constructive criticism

Now are you getting it?

Originally Posted by mitiempo

You are going to a hell of a lot of trouble to eliminate a bit of wire loss that could easily be reduced with a larger wire.

This guy's forgotten more than most of us have learned about this stuff so far.

You listening?

[newhaul]

John , paul I hope you two can have more luck with the recomendations than I seem to have had .
Tommorrow im doing the install of the new pair of 100 watt panels on my new to me defender.

[Kenomac]

Originally Posted by jheldatksuedu

let's look at an imaginary typical system, 3 100 watt 12v panels = 8 amps per panel

installed in parallel at the back of a sailboat to reduce shading problems, thus 24 amps in a wire.

30 feet of wire from panels to controller to 4 batteries in parallel. 10 gauge wire can handle 55 amps and has 1 ohm/1000 ft, .03 ohms in 30 ft

wire loss = 24x24x.03 = 17.3 watts

wire loss percentage 17.3/300 = 5.67%

one website I just looked at said 3 to 5% is acceptable, so probably switch to 8 gauge, but we are just trying to illustrate a point here, so I won't re do the calculations.

-----------------

Now let's put the controller near the panels and increase voltage in the wire to the batteries to 48 volts in series, same 10 gauge wire.

300 watts/48 volts = 6 amps
loss is 6x6x.03 = 1.08 watts

wire loss percentage 1.08/300 =.0036%

Sure there's lot of things you can change here but this just looks at what could be considered a typical system and my proposed changes. I also just realized that the wire length needs to be doubled, you have to have 2 wires to make a circuit, that would double the loss, so definitely go to 8 gauge, but still the same dramatic difference for reasonable sized wires and system. So my system in addition could reduce the wire size needed and the expense of larger wires.

Do you still think you need to tell me to KISS?

Seems like an incredible amount of trouble to go through just to save a few dollars on some wire. Just use the appropriate size for the runs from the panels to the controller, then place the controllers next to the battery bank as recommended by the manufacturers.

[StuM]

Originally Posted by john61ct

Now are you getting it?
This guy's forgotten more than most of us have learned about this stuff so far.

You listening?

I keep thinking back to this post earlier in the thread:

"Please correct me if I'm wrong, I'm new at this with no practical experience".

He seems very reluctant to accept the requested corrections.

[ramblinrod]

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 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.

At what institution did you teach electrical engineering?

Making this as simple as possible so that you can follow...

With 3 virtually open circuit (fully charged) batteries in series with one virtual short circuit (discharged) battery, what kind of charge current do you expect to get through that discharged battery, with a charge controller connected across the bank?

Oh shoot, this isn't going to be another Kirchoff's Law lesson is it?

[ramblinrod]

Originally Posted by jheldatksuedu

You just refuse to get it, you can't see the forest because your too busy beating your head against a tree, I'm asking for constructive criticism, I could care less that your 100 watt panel puts out 6 amps and I assume mine does 8, that's not the point here, I'm just giving an example, making up numbers off the top of my head, (100 watts divided by 12 volts is 8 amps) and I could care less that you use 6 gauge wire and my calculations were done with 10, I also could care less if a user manual says put the controller near the battery, I'm showing your that maybe you don't want to do that. And as far as not being concerned about losses between the panel and controller, granted that's not going to affect if the battery will charge but it still is a loss of energy and affects the entire efficiency of the system. It's still a loss, and could be major. That's one of the reasons that we might want to put panels in series, increase the voltage and reduce wire loss. But then have the risk of the entire system shutting down when one corner gets shaded. Basically, If you don't have anything constructive to say, then please just shut up.

I'm convinced that my system could work and reduce losses, might reduce cost but has to have a fancy switch. If you can show me why it would not work I'm all ears, but just criticizing my choice of 8 amp panels and 10 gauge wire in my imaginary example is not going to do that. 5% loss in the wires is said to be an acceptable amount, my system can reduce that to .3% giving you 4.7% more power to charge the batteries. If your system has only 2% loss in the wire this can still save you 15/16 of that loss. I'm not talking about trying to reduce losses in an already built system, I'm talking about designing a system that has less loss and maybe cost from the start.

You call yourself a Marine Service Provider, I certainly would have a hard time recommending your "service" to anybody. I really hate to lash out at somebody like this but sometimes I have to call a spade a spade.

I'll try to make this as clear and respectful as I can.

Your theory and comments are severely flawed.

I was going to list them one by one, but that would take far too long, and my suspicion based on your prior comments is that you would simply ignore them anyway.

So I can wrap it all up with one simple suggestion.

Take a basic electrical course, before touching a marine electrical system, or you are likely to hurt yourself or others around you.

PS, you would be very wise to be much more respectful of the knowledgeable marine electrical professionals (and others) here, who are taking time out of their busy lives, to try to help you (at no charge I may add).

[jheldatksuedu]

There are losses in all electrical systems, but with solar we are working with such small amounts of energy so it is important to conserve what ever we can. Sure you can solve this with bigger wires, and I understand why you want to put the controller near the battery but if you don't have the voltage loss through the wires then the controller can read the voltage of the battery acurately 30 feet away and do a good job of charging. Bigger wires ad cost and weight. We all spend a lot of time attempting to eliminate both of those.

I taught at Kansas State University for 30 years, Physics, Mechanical Engineering and Electrical enginneriing.

I have not forgot my electronics, I know exactly what I am proposing and thought it out very well. What you refuse to seem to realize is that ther might be more than one way to do the same problem. New Ideas are often scoffed at by people unwilling to challenge the staus quo.

[Kenomac]

The directions on my Genasun GV Boost controllers seems very clear....

CAUTION for the GVB-8-pb

INTERNAL TEMPERATURE COMPENSATION. RISK OF FIRE, USE WITHIN 0.3m (1ft) OF BATTERIES.

Capitalized and emphasized in the instruction/installation manual.


So then why would somebody decide that "it doesn't matter" where he puts them? And that the primary goal should be saving pennies on wire. Seems like priorities are a little goofed up.

But then what do I know? I'm usually the one turning to the CF knowledge base for help with these matters. AND SO FAR IT'S WORKED OUT GREAT!

[john61ct]

48V house systems are not a new idea.

Just so rare as to be unnecessarily expensive, for most prohibitively so, compared to a few extra pounds (if that) of copper.

I just don't see the sense in it myself, but preserving my limited funds is a high priority, for me.

If you are indeed aware of what it will cost you and want to invest that in your experiment, your boat, your call.

Just do get guidance from a pro **experienced** at these EV voltages, to follow the very different safety codes when you go over 50V, so you don't kill anyone.

[john61ct]

Here is where you started

Originally Posted by jheldatksuedu

I have a question about solar panel charge controllers, are there any things to watch out for or to look for when making a purchase. Do they typically take higher solar panel voltage and convert it to lower battery voltage and more charging amps, or do they just basically block current to keep the battery from over charging? How about low voltage from a shaded panel, do they convert that to battery voltage and less current to get some good out of it.

Is this what they do, (I would hope) or am I expecting too much from a $50 item?

Originally Posted by jheldatksuedu

Everything I do is about saving a few dollars, I bought my boat for $5000

Well here's a place to spend that money you've been saving!

[john61ct]

Not to mention that whacky "automated switching system" to pull 12V for loads out of the each battery in the 48V series string.

You're not still considering that are you?

Out on the water KISS isn't just lifestyle advice. #1 priority has to be safety, closely allied to reliability.

Proven best practices are there to be followed. You do want insurance right?

After you've become a hands-on expert in the standards with years of experience, THEN start coming up with radical new scenarios, and by then you'll be sensible enough to test them out on land. . .

[ramblinrod]

Originally Posted by jheldatksuedu

There are losses in all electrical systems, but with solar we are working with such small amounts of energy so it is important to conserve what ever we can. Sure you can solve this with bigger wires, and I understand why you want to put the controller near the battery but if you don't have the voltage loss through the wires then the controller can read the voltage of the battery acurately 30 feet away and do a good job of charging. Bigger wires ad cost and weight. We all spend a lot of time attempting to eliminate both of those.

I taught at Kansas State University for 30 years, Physics, Mechanical Engineering and Electrical enginneriing.

I have not forgot my electronics, I know exactly what I am proposing and thought it out very well. What you refuse to seem to realize is that ther might be more than one way to do the same problem. New Ideas are often scoffed at by people unwilling to challenge the staus quo.

Dude, if anyone knows about challenging the status quo, I do.

But your idea is seriously flawed.

I think you are so busy contemplating the forest, you are ignoring the single tree that is smacking you square between the eyes.

If you did actually teach Electrical Engineering, go back and revisit Day One, Lesson One - Kirchoff's First Law.

In a series string of 4 batteries, the 3 fully charged batteries will represent a high impedance and limit charge controller current available to the fourth discharged and loaded battery.

If the total impedance of the 3 fully charged unloaded batteries will only accept 2 A (lets say), that is what the available charge current to your loaded discharged battery will be, regardless what the system is capable of producing at max load.

So if your max charge current is limited to 2 A, how does this impact your (theoretical) wire loss calcs?

The Status Quo has been challenged and unfortunately, you lost.

[jheldatksuedu]

If you will look between the trees that are blocking your view you will find that I don't intend to have one battery fully discharged, even though I did ask what would happen if that was the case. I mentioned switching between batteries numerous times to have them equally discharged, but wondered what would happen if one was more discharged than the rest. I have decided that would not be a problem, the other three batteries would allow current to flow, if too much current flows they will boil, but I'm pretty sure that their voltage would increase enough that the current would be limited by the controller and not cause that damage, and the discharged battery will eventually charge back up. Worst case I foresee could be a 10 and 3 12's, the 12's would increase to something above 14.7 and total series voltage would then give a total of 54.1 plus some for the slight over voltage due to excessive charging, the 48 volt charger would be programmed to slow down before it nears 58.8 so you would basically have 4 volts pushing extra current through the series of batteries. I suspect that would be OK, but have not tested it yet.

It sure would be nice if you people would take the time to understand what I propose and not jump on the band wagon to call me stupid. I am not stupid.

I'm basically done here I'm not finding anyone that has any knowledge of this type of system that can answer my questions and I'm tired of trying to teach people who have no desire to learn. Stay with your status quo and be happy with your ignorance.

[john61ct]

I didn't see anyone say stupid. But I still haven't seen any persuasive rationale for what would make the whole exercise worth pursuing, other than curiosity,

Buy your four batteries, a high-amp 48V charger, a good DMM and clamp ammeter, do the dis/connecting manually for now, and report back on the results of your 4S experiment.

That way you can always go to 4P 12V or 2P2S 24V later, hardly out of pocket.

If you don't hurt the batteries.

[atlantical]

You lot make everything way too complicated. I didn't have all these problems getting my solar up and running. The battery voltage can be noticeable though, if one battery charges to a higher voltage than the other, charge the two together, and you only get the lower voltage, charge them individually, and you get a high voltage battery and a low voltage battery.