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culwatty

New Member
Joined
Sep 16, 2021
Messages
3
Hello!

So I'm currently living aboard a boat in the UK, no external power, a few old panels hung off the railings.... so I decided to change a few things, and Wills videos Have taught me so much!

So, I'm looking at going 48v on the boat, for reasons like later on electric propulsion but I"ll try not to get carried away!

So part of my "problem" is that its a sailboat, so shading is a massive issue, I looked around and found the Panasonic HIT modules with a Vpmax of 59.7v planning on running them in parallel

I can't find any other panels with such high voltage on a single panel despite lots of googling and searching, am I missing some simple terminology? does anyone know of any panels?

I have searched but again, might be using the wrong terms!?

Anywho

I look forward to meeting everyone :)
 

FilterGuy

What, me worry?
Joined
Nov 26, 2019
Messages
4,458
Location
Los Gatos CA
Welcome to the Forum.
So part of my "problem" is that its a sailboat, so shading is a massive issue, I looked around and found the Panasonic HIT modules with a Vpmax of 59.7v planning on running them in parallel

I can't find any other panels with such high voltage on a single panel despite lots of googling and searching, am I missing some simple terminology? does anyone know of any panels?
You seemed to make a leap that I did not follow. How does voltage and shading relate? (Or is there some other reason you are looking for higher voltage panels?)

I can't find any other panels with such high voltage on a single panel despite lots of googling and searching, am I missing some simple terminology? does anyone know of any panels?
59.7V is about as high as I have ever seen..... but more times than not I am wishing the panel voltage was *lower* so I am never looking for higher voltage panels.
 

culwatty

New Member
Joined
Sep 16, 2021
Messages
3
Welcome to the Forum.

You seemed to make a leap that I did not follow. How does voltage and shading relate? (Or is there some other reason you are looking for higher voltage panels?)


59.7V is about as high as I have ever seen..... but more times than not I am wishing the panel voltage was *lower* so I am never looking for higher voltage panels.

Hi!

Sorry, so I plan on moving to a 48v Lifepo4 battery, so I was trying to plan for panels to run parallel to separate controllers if this makes sense?

I am curiose, why are you searching for lower voltage panels? I thought higher voltage was good for MPPT?

Thanks for your interest so far!
 

Short_Shot

Photon Sorcerer
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Jul 13, 2021
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1,811
Higher voltage is better but it's essentially irrelevant as long as your panels are 5 or so volts above your charge output voltage.

If you put panels in series you run up against shading concerns affecting output but you don't just lose the entire voltage of that panel in the shade. Their voltage is relatively stable despite shading.

Now. I could be wrong, but as I understand it putting two in series and shading one of them doesn't significantly decrease voltage but you'll still lose the current from that shaded panel.

If that's true then there's no reason you can't just stick the two in series with an appropriate combiner method that includes bypass diodes. You'll then have ~120vdc and can use a 150v solar charge controller.

And then you can put as many strings of two panels into parallel as you can support with the chargers current/wattage rating.
 

culwatty

New Member
Joined
Sep 16, 2021
Messages
3
Higher voltage is better but it's essentially irrelevant as long as your panels are 5 or so volts above your charge output voltage.

If you put panels in series you run up against shading concerns affecting output but you don't just lose the entire voltage of that panel in the shade. Their voltage is relatively stable despite shading.

Now. I could be wrong, but as I understand it putting two in series and shading one of them doesn't significantly decrease voltage but you'll still lose the current from that shaded panel.

If that's true then there's no reason you can't just stick the two in series with an appropriate combiner method that includes bypass diodes. You'll then have ~120vdc and can use a 150v solar charge controller.

And then you can put as many strings of two panels into parallel as you can support with the chargers current/wattage rating.
That sounds roughly like what I thought, as 50% of the boat is going to be shaded I wanted to minimize losses, but finding the HIT Panels at a reasonable price is what I'm struggling with, running them in series makes sense as I've already got 150/20 victron MPPT But I wanted to see if any other panels are cheaper and still offering the higher voltage as my minimum voltage with one panel down is still 60v -+

So I guess what I'm asking is, does anyone know of another brand available in the UK that's pushing similar voltage? and the voltage is dictated by the amount of cells in series I'm guessing so maybe I need to search for panels with more cells!...... will report back
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,811
You don't need to worry about finding a specific voltage. Just buy the panel based on dimensions and wattage and put them in series if you need more voltage.
 

FilterGuy

What, me worry?
Joined
Nov 26, 2019
Messages
4,458
Location
Los Gatos CA
I am curiose, why are you searching for lower voltage panels? I thought higher voltage was good for MPPT?

Higher total voltage is good, but that does not always translate into higher panel voltage being better.

In order to minimize wire size I try to maximize the number of panels in series (Maximize string voltage). Quite often I would like to add one more panel to the series string but the Voc is just a little too high to add the panel and still have the buffer I want for temperature rise. I can sometimes find a panel that has a slightly lower Voc that allows the extra panel. The panel can even be slightly lower wattage but it still works out to being higher over-all wattage by having the extra panel.

Of course there are many other factors at play that go into the final design. Like you mentioned shading can impact things and space for the panels can be limited. As with any engineering problem, it is always a trade-off among many different factors.
as 50% of the boat is going to be shaded I wanted to minimize losses,
Having a controller per panel is a good way to help minimize losses, but Bypass diodes can make a big difference too

In your case, even with a controller per panel, you should be looking for panels with two or three bypass diodes. That way if part of the panel is shaded, it is less likely to impact the output of the whole panel. (A lot of panels are designed with 3 bypass diodes. Each diode will bypass a stripe that runs the long dimension of the panel. )

In addition, if there are panels in parallel, blocking diodes can help prevent the shading on one impact the output from the other.

 
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