Shaded Panels - Catamaran Boom

[hzcruiser]

Looks like there is a fixed bimini where you can't walk on anyway, correct?

Another consideration: Going with the "many MPPT"s option would mean to run quite a lot of cables from up there all the way down.

So to recap: you have 15 500W panels that you want to connect and you have 4 MPPT controllers?

Looking at the controller's specs, their operating voltage looks very high? 120-450 VDC ? That's some serious voltage, as in lethal...

With so much solar power (7.5kW ?) I would recommend engaging a professional to design a proper system.

[ArranP]

Thank you for your reply.

Originally Posted by hzcruiser

Looks like there is a fixed bimini where you can't walk on anyway, correct?

Correct, however in later editions Lagoon have incorporated a plank into the bimini.

Originally Posted by hzcruiser

Another consideration: Going with the "many MPPT"s option would mean to run quite a lot of cables from up there all the way down.

So to recap: you have 15 500W panels that you want to connect and you have 4 MPPT controllers?

I anticipate between 15 and 20 panels each being 550w so total 11KW

Originally Posted by hzcruiser

Looking at the controller's specs, their operating voltage looks very high? 120-450 VDC ? That's some serious voltage, as in lethal...

With so much solar power (7.5kW ?) I would recommend engaging a professional to design a proper system.

The MPPT controller can go as high as 450VDC, however 11KW across 4 MPPT controllers is 2.75KW ( 5 or 6 panels ) per MPPT.

Each panel is 50V 11A

5 panel config : 1 string of 5 panels 250V ( 5x 50V ) 11A
6 panel config : 2 strings of 3 panels 150V ( 3x 50V ) 22A

I am not an electrician and I am not saying that I am an expert but I have been living off-grid for 3 years now and did install and cable my solar system, I have no connection to the grid.

I do concede to the issue of risk with high voltage or high amperage on the boat or in a marine environemnt, and will continue to research into this. I have read that it is the amps that kill not the volts, that said I would not like to receive a shock from my 48V battery let alone my 250V string of panels.

But then again on the boat there will be 220V AC, a similar voltage to the 250V DC coming from the panels.

[hzcruiser]

Originally Posted by ArranP

5 panel config : 1 string of 5 panels 250V ( 5x 50V ) 11A
6 panel config : 2 strings of 3 panels 150V ( 3x 50V ) 22A

I am not an electrician and I am not saying that I am an expert but I have been living off-grid for 3 years now and did install and cable my solar system, I have no connection to the grid.

I do concede to the issue of risk with high voltage or high amperage on the boat or in a marine environemnt, and will continue to research into this. I have read that it is the amps that kill not the volts, that said I would not like to receive a shock from my 48V battery let alone my 250V string of panels.

But then again on the boat there will be 220V AC, a similar voltage to the 250V DC coming from the panels.

Well, I am a qualified electrical engineer but that doesn't mean you have to follow my advice. It's just a word of caution, in particular since AC and DC are quite different beasts. In the past I got zapped by 220V AC a few times where DC would've been lethal: With 50 or 60 Hz AC you get those brief moments of no voltage (and no current) 50 (or 60) times per second. As your muscles contract, this allows you to "let go" of the live wire. With DC, the voltage is always there and makes you "sticky" unless a breaker trips beforehand...

[hzcruiser]

And by the way, a 48V battery won't zap you. In fact, that's considered the safe limit, where the skin resistance is high enough to prevent current flow. Anything above 90V though could cause you trouble.

Also, a few dozen milliAmps are enough to stop your heart from beating. So yes, current can kill us, but voltage gets the current "under your skin".

[more]

Originally Posted by hzcruiser

And by the way, a 48V battery won't zap you. In fact, that's considered the safe limit, where the skin resistance is high enough to prevent current flow. Anything above 90V though could cause you trouble.

Also, a few dozen milliAmps are enough to stop your heart from beating. So yes, current can kill us, but voltage gets the current "under your skin".

i think over 40V is danger

[ArranP]

Originally Posted by hzcruiser

And by the way, a 48V battery won't zap you. In fact, that's considered the safe limit, where the skin resistance is high enough to prevent current flow. Anything above 90V though could cause you trouble.

Also, a few dozen milliAmps are enough to stop your heart from beating. So yes, current can kill us, but voltage gets the current "under your skin".

I have found that DC that I have been ok when holding solely the negative wire or soley the positive wire.

However with AC it is different... I have been ok holding the negative wire ( which is in fact the ground I believe ) but when holding soley the positive wire I get a shock.... probably because I am then acting as the short to ground.

The Victron installations on boats I usually see one mppt per panel, presumably this is to avoid the risk of high DC voltage.

The off-grid homes though all of those installations are strings going up to 450V, and those MC4 connectors I've had some melt on me.

To summise, the risk is here coming into contact with BOTH the negative and positiver wires of the string, what are the odds and how would / could that happen..... i suppose if the positive & negative wires rubbed bare against seperate steel posts and then I ( or someone else ) grabbed onto both posts that would be it.

Silent Yahcts have a completely electric powered yacht, no sails just an array of panels covering the whole top. The 60ft model has 46 panels, I esimate 20kw... the question then do they use a seperate mppt for each panel or use strings ? If strings, then what voltage have they gone upto and are what steps have been taken to guard against shock.

[ArranP]

Originally Posted by hzcruiser

Well, I am a qualified electrical engineer but that doesn't mean you have to follow my advice. It's just a word of caution, in particular since AC and DC are quite different beasts. In the past I got zapped by 220V AC a few times where DC would've been lethal: With 50 or 60 Hz AC you get those brief moments of no voltage (and no current) 50 (or 60) times per second. As your muscles contract, this allows you to "let go" of the live wire. With DC, the voltage is always there and makes you "sticky" unless a breaker trips beforehand...

Silent yachts use several 150V mppt charge controllers on their silent 55 / 60.

https://www.victronenergy.com/blog/2...ruising-yacht/

[fivecapes]

Originally Posted by ArranP

Silent yachts use several 150V mppt charge controllers on their silent 55 / 60.

https://www.victronenergy.com/blog/2...ruising-yacht/

I wonder if the Victron tech people had a few words with their marketing/web department for showing that install.

[ArranP]

Originally Posted by fivecapes

I wonder if the Victron tech people had a few words with their marketing/web department for showing that install.

The piont being...

Each of the cables returning from the panels via the fuse holders are numbered.

Each of the MPPT controllers are also numbered.

The number on the fuse holder corresponds to the number on the MPPT controller, thus we know which cable is going to which MPPT controller.

There are 22 fuses, so I assume 22 panels... therefore in this installation there are no strings of panels ! only panels connected in parallel at the MPPT controller.

So this would be to avoid High Voltage DC.

The question remains is why do marine based installations promote the use of solar panels in parallel whilst land based home solar installations promote the use of solar panels in series ( using upto 450V DC MPPT Solar Charge Controllers ) ?

[hzcruiser]

Originally Posted by ArranP

I have found that DC that I have been ok when holding solely the negative wire or soley the positive wire.

However with AC it is different... I have been ok holding the negative wire ( which is in fact the ground I believe ) but when holding soley the positive wire I get a shock.... probably because I am then acting as the short to ground.

I'm not sure I would do you a favour in explaining this as I don't want to regret it one day, as in hearing from a fatal accident by DC voltage on a boat...

To be brutally honest, I'm afraid you don't have the necessary basics (yet) to assess the dangers involved here.

As in: with AC there is no negative or positive wire, one is live, the other is neutral, the third one is protective earth. Life is going from zero to +220V, then back to zero, then to -220V relative to neutral. This is not easy to understand from one sentence, though. Protective earth (or PE) should never carry any current unless something went horribly wrong, in which case it should trip the fuse.

If you didn't know about this, I would express my recommendation again to get a certified marine electrician to at least look over your schematics or plan of wiring it all up.

The Victron installations on boats I usually see one mppt per panel, presumably this is to avoid the risk of high DC voltage.

Very likely, and if so, for a good reason: to save life.

To summise, the risk is here coming into contact with BOTH the negative and positiver wires of the string, what are the odds and how would / could that happen..... i suppose if the positive & negative wires rubbed bare against seperate steel posts and then I ( or someone else ) grabbed onto both posts that would be it.
[...]

Not quite, I'm afraid.

Your panels are putting out 50V DC each, if you put three in series, that's 150V DC between the positive and the negative wire. However, you have to assume that the panel frame is also connected to the boat. On my steel sloop, that's certainly the case. So if you stand bare-foot on deck touching the positive wire of your panels, you're in great danger right there.

On my boat, I limit the DC voltage from the panels to 48V no matter what. This goes to the charge controllers that turn it into 12-14V for the LFP and FLA batteries.

Good luck, fair winds and stay safe!

[hzcruiser]

Originally Posted by ArranP

[...]

There are 22 fuses, so I assume 22 panels... therefore in this installation there are no strings of panels ! only panels connected in parallel at the MPPT controller.

So this would be to avoid High Voltage DC.

The question remains is why do marine based installations promote the use of solar panels in parallel whilst land based home solar installations promote the use of solar panels in series ( using upto 450V DC MPPT Solar Charge Controllers ) ?

22 fuses? That sounds like a lot... and in general, you don't need to fuse a panel anyway. A fuse is there to protect the wiring from catching fire. A fuse at the end of a wire is pretty pointless. Maybe the wiring is done some other way?

As to your other question, on a boat, lots more things can and will go wrong over time, with wind and salt water involved...

[ArranP]

Originally Posted by hzcruiser

I'm not sure I would do you a favour in explaining this as I don't want to regret it one day, as in hearing from a fatal accident by DC voltage on a boat...

To be brutally honest, I'm afraid you don't have the necessary basics (yet) to assess the dangers involved here.

As in: with AC there is no negative or positive wire, one is live, the other is neutral, the third one is protective earth. Life is going from zero to +220V, then back to zero, then to -220V relative to neutral. This is not easy to understand from one sentence, though. Protective earth (or PE) should never carry any current unless something went horribly wrong, in which case it should trip the fuse.

If you didn't know about this, I would express my recommendation again to get a certified marine electrician to at least look over your schematics or plan of wiring it all up.



Very likely, and if so, for a good reason: to save life.



Not quite, I'm afraid.

Your panels are putting out 50V DC each, if you put three in series, that's 150V DC between the positive and the negative wire. However, you have to assume that the panel frame is also connected to the boat. On my steel sloop, that's certainly the case. So if you stand bare-foot on deck touching the positive wire of your panels, you're in great danger right there.

On my boat, I limit the DC voltage from the panels to 48V no matter what. This goes to the charge controllers that turn it into 12-14V for the LFP and FLA batteries.

Good luck, fair winds and stay safe!

Thank you.

Yesterday, I read about "common ground" on boats... The AC Earth and DC Negative are interconnected via the common ground busbar which also has the chasis of the boat is connected to it ( ABYC US not European ) making the boat DC Negative.... Assuming the panels are also connected to this DC Negative commong ground, one would only need to touch a positive wire from one of the panels to receive a shock as the connection would be between DC postive wire and boat itself being DC negative.... However these are regulations for USA only. In Europe ( Maybe Aus ) I gather regulations don't stipulation this interconnection between AC Eath and DC Negative, which maybe the piont that you were reluctant to convey, as you did not want me go de-coupling the DC Negative fromt the commond busbar, and assume I would then be safe having done so.

That said I do take heed of this... the trade-off being 1. saving a few dollars on charge extra controllers compared to 2. loosing a life of someone dear to me... Not much though needed there ! Thank you for taking your time to steer me to right way. ( My house doesn't move and the panels are way up on the roof, out of harms way )

Moving forward ( and putting the panel issue to one side ), is it better to NOT connect the DC Negative to the chasis of the boat ? The DC voltage on my is 24V ( as it is it on larger boats ). Making the whole boat 24V DC Negative is surely a step closer to getting a shock ?

Referencecs https://newboatbuilders.com/pages/electricity1.html
https://www.cruisersforum.com/forums...c-72432-3.html

[ArranP]

Now I am in a dilema... opposing viewpoints.

Having chatted with a neighbour of mine, who is an electrician and also has his own yacht, the reason for paralleling panels is to do with shading rather than mitigating the risk of high voltage dc.

The risk of harm from high voltage dc cabling is down to the installation ie. plastic conduit, if the installation is done correctly, and the circiut is isolated before being worked on, then there is no problem with having high voltage dc on a boat.

[hzcruiser]

Originally Posted by ArranP

[...]

However these are regulations for USA only. In Europe ( Maybe Aus ) I gather regulations don't stipulation this interconnection between AC Eath and DC Negative, which maybe the piont that you were reluctant to convey, as you did not want me go de-coupling the DC Negative fromt the commond busbar, and assume I would then be safe having done so.

[...]

Moving forward ( and putting the panel issue to one side ), is it better to NOT connect the DC Negative to the chasis of the boat ? The DC voltage on my is 24V ( as it is it on larger boats ). Making the whole boat 24V DC Negative is surely a step closer to getting a shock ?

Referencecs https://newboatbuilders.com/pages/electricity1.html
https://www.cruisersforum.com/forums...c-72432-3.html

From your reference list I can see you're doing your due diligence, good on you! And you already noticed that even the different standards have varying recommendations...

To quickly answer your questions: DC negative should or is generally connected to "chassis", as you call it, through the engine block and the starter motor anyway. Also the engine is connected to the outside water via the prop shaft. That's why it's the "normal" thing to do, connecting the battery minus to the engine.
The recommendation you read in other forum threads about having exactly one ground has to do with electrolysis issues, not electrocuting yourself.

In your first paragraph you mention "AC earth". I would reiterate that AC has the phase (or life wire) and neutral, which is "return". The third wire is then protective earth (PE) and should _not_ carry any current but rather trip the breaker if it is. That's how it's protecting you.
But there is more to that and whether or not connecting PE to battery minus or the engine... that's why I recommended getting a pro involved.

[hzcruiser]

Originally Posted by ArranP

Now I am in a dilema... opposing viewpoints.

Having chatted with a neighbour of mine, who is an electrician and also has his own yacht, the reason for paralleling panels is to do with shading rather than mitigating the risk of high voltage dc.

The risk of harm from high voltage dc cabling is down to the installation ie. plastic conduit, if the installation is done correctly, and the circiut is isolated before being worked on, then there is no problem with having high voltage dc on a boat.

Not quite opposing, more like both options have their merits...

And yes, high DC voltage (as in >48V) is not per se wrong on a boat, only running an additional conduit through the boat is much more involved than just routing the wires directly as part of the bigger loom.

Furthermore please keep in mind the standards likely also prohibit running high DC (or AC) voltage through the same conduit as low voltage DC, hence a second conduit is needed.