Challenges with Solar on boats

[foggysail]

Originally Posted by newhaul

New 5000W 5kw 36V Solar Panels Home Power Generator Free Shipped By Sea | eBay

http://vi.raptor.ebaydesc.com/ws/eBa...35&cspheader=1

GREAT PRICE.................now add the tariff

[john61ct]

Originally Posted by newhaul

New 5000W 5kw 36V Solar Panels Home Power Generator Free Shipped By Sea | eBay

These panels are 36 volt
Here is the page with the specs.

http://vi.raptor.ebaydesc.com/ws/eBa...35&cspheader=1

Yes they are. And all such panels, from 34V up to say 44V could be called 24v nominal.

12V nominal starts around 18V.

[john61ct]

The Victron MPPT includes a "buck" DC converter circuit that converts the higher-voltage lower-amp panel output, to lower-volt higher-amp.

WAG scenario, 220W output to the SC at 30V, around 7A. If the bank's charge voltage is around 14V, there's your 15A.

Yes at some peak times, some small percentage will be discarded. But the controller will be outputting close to or at its maximum a higher percentage of the time.

And shading effects are minimized.

Best value for money spent IMO.

[newhaul]

Originally Posted by john61ct

The Victron MPPT includes a "buck" DC converter circuit that converts the higher-voltage lower-amp panel output, to lower-volt higher-amp.

WAG scenario, 220W output to the SC at 30V, around 7A. If the bank's charge voltage is around 14V, there's your 15A.

Yes at some peak times, some small percentage will be discarded. But the controller will be outputting close to or at its maximum a higher percentage of the time.

And shading effects are minimized.

Best value for money spent IMO.

Scenario its ten am and your panels are putting out 38 volts at aprox 9 amps. Your batteries were tapped hard last night so they are at 12.6 now you have aprox 25 amps available but your 15 amp controller is discarding 10 amps due to limits. Not what I would call a good deal. Imho. ( numbers aproximate for illustration only)

[Quadrille in JB]

With the help of Alex at SeaTek Marine in Marathon I installed a single Sunpower 360W/70V panel on my little 27' Watkin's dingy davits using a Victron 100/30 MPPT. This setup works great. The Victron has a bluetooth interface to my iPhone which provides real time output as well as a 30 day history. When powering an isotherm ref/freezer, a PUR Survivor 35 watermaker, Simrad autopilot, large Garmin chart plotter, a 2000w inverter, a fan and various other items on the boat it often outputs slightly in excess of 360 watts. My house bank is 4-105 amp AGMs with a single 85 amp AGM for starting. I charge all of these at once using several Guest battery selectors. This just shows that you can add a lot of comfort to a small boat with a single high quality solar panel, MPPT controller, and adequate battery bank.

[john61ct]

Originally Posted by newhaul

Scenario its ten am and your panels are putting out 38 volts at aprox 9 amps.
...
( numbers aproximate for illustration only)

No, those numbers are **pure** fantasy, not even in the ballpark.

Even in clear skies at the equator on top of a frozen mountain with a natural bowl of snow focusing a noon sun's rays on that panel.

[newhaul]

Originally Posted by john61ct

No, those numbers are **pure** fantasy, not even in the ballpark.

Even in clear skies at the equator on top of a frozen mountain with a natural bowl of snow focusing a noon sun's rays on that panel.

John it seems you edited your post but here is my real world answer to your challenge. I curently have 2 100 watt mono panels from renogy, a p30l pwm charge controller and for the last month ( untill the smoke moved in from. BC I was averaging 8 to 10 ah from 9 am untill 4pm which is 7 hours from 9 to a out 1030 say 10 ah and the same again from 230pm to 4 pm another 10 ah and max of 10 to 11 ah for the middle 4 hours for a total of 60 ah from 9 to 4 and lesser on the outside . I begin showing 1/2 amp out of the panels aprox 1hour after sunup and the same on the other side. Till sundown. So it seems I already have well over 60 ah out of 200 watts on a pwm controller. ( yes thats all provable)

[StuM]

Originally Posted by newhaul

Scenario its ten am and your panels are putting out 38 volts at aprox 9 amps. Your batteries were tapped hard last night so they are at 12.6 now you have aprox 25 amps available but your 15 amp controller is discarding 10 amps due to limits. Not what I would call a good deal. Imho. ( numbers aproximate for illustration only)

38 * 9 = 342 W at 10:00 am. That would suggest that you have around 400W of solar. No?

[StuM]

Originally Posted by john61ct

Actually it's 220W at "nominal 12V" usually 17+V

But his panels are nominal 24V (actual 32V) where the max rating is 440W.

It really is the Voc (first number in model) that is critical for sizing, especially in cold climates.

The lsc short circuit amps maximum rating for both the 75/15 and 100/15 models is 20A.

Nope, the max rating is for 24V batteries, not 24V panels.

The limiting factor is still the charging current of 15A.

[newhaul]

Originally Posted by StuM

38 * 9 = 342 W at 10:00 am. That would suggest that you have around 400W of solar. No?

Stu you are right I wasnt paying much attention to my numbers ( had some steaks on the q and they needed my full attention) was going off the numbers from another poster ( should have checked my math )
Lets say 32 volts output . With the 9 amps.

[mitiempo]

Originally Posted by john61ct

With Victron, you need to be careful to not exceed the voltage, so for the 100/15 unit, stay under 100V total panel Voc. Looking at just that factor you could safely put two 38.8V panels in series.

However there is quite a safety factor built into the second max Amps rating, which is **charging** amps; by exceeding that 15A you will "waste" some power output in (rare) peak conditions, but output a higher total power in average conditions, IMO a good value tradeoff.

However, the ideal for protection against shading losses is one SC per panel. For that purpose 75/15 would be fine, and IMO cheap at under $100 delivered.

There are 2 limits in play with any controller. Maximum panel wattage and maximum solar array voltage.

The Victron 75/15 is limited to 200 watts of panels. You can use 1000 watts if you wish - there will not be any damage to the controller. It will however limit the incoming panel wattage to 200. It is not logical to use the 75/15 with more than 200 watts of panels.

[mitiempo]

Originally Posted by newhaul

The ratings on mppt controller s is max voc and amps. You have a36 volt panel putting out a max of 9.58 amps . To charge a 12 volt house bank you are reducing the voltage by a factor of 3 which will increase the amps out by a factor of 3 which would give you an approximate amp to the batteries of 28.75. So yes you would need a controller rated for 30 amps output.

Actually a factor of 2, not 3. The panels are nominal 24 volt panels. Remember a 12 volt nominal panel is usually 19 to 20 voc. Double that for 24 volt nominal panel and you get 38+ volts.

Amperage doubles to about 19.

[mitiempo]

Originally Posted by CapnCrunch

I'm not getting this. The Victron 100/15 specs read "Maximum PV power, 12V 1a,b): 200W (MPPT range 15V to 100V)"

My 290w panel specs show "Voc = 38.8VDC/ Isc = 9.58 A. I thought the Victron model numbers represented Voc/Isc?

If panel wattage is the determining factor, it looks like I would have go to the 150/35 at a cost of $295 ea vs. $90 ea for the 75/15. And, since the 150/35 is rated for 650W, I would need two of them . The damned panels only cost $175 ea, so I would be spending more for the controllers than for the panels.

The Victron 100/30 will work fine with each panel and is less expensive than the 150/35 by a fair bit.

[newhaul]

Originally Posted by mitiempo

Actually a factor of 2, not 3. The panels are nominal 24 volt panels. Remember a 12 volt nominal panel is usually 19 to 20 voc. Double that for 24 volt nominal panel and you get 38+ volts.

Amperage doubles to about 19.

Yea I noticed that after I did the thunking with the statement of it being a 36 volt panel. So even with a 24 volt panel and that controller they would be wasting as much as 20 ah per day . Still worth getting a bigger controller imho.

[mitiempo]

Originally Posted by john61ct

Actually it's 220W at "nominal 12V" usually 17+V

But his panels are nominal 24V (actual 32V) where the max rating is 440W.

It really is the Voc (first number in model) that is critical for sizing, especially in cold climates.

The lsc short circuit amps maximum rating for both the 75/15 and 100/15 models is 20A.

The 220 watts is an error on some Victron literature, or their website. 200 is the maximum wattage for the 75/15.

With a Victron controller you can double panel wattage if your battery system is 24 volts. The voltage of the panels doesn't relate to maximum wattage.

https://www.victronenergy.com/upload...E-ES-SE-LU.pdf

The specifications are on page 9