Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 23-05-2015, 15:19   #31
Eternal Member
 
monte's Avatar

Cruisers Forum Supporter

Join Date: Jul 2011
Location: Australia
Boat: Lagoon 400
Posts: 3,650
Images: 1
Re: Solar Panel efficiency - Should I upgrade

sorry for the confusion, I meant we use 20 Ah continuously, ie 480 A/day
Panels put out around 50 Ah for around 8 hrs/day with the shading and limited November sunlight hours
I think we should be right next passage by cutting back on usage
__________________

__________________
monte is offline   Reply With Quote
Old 23-05-2015, 15:20   #32
Registered User

Join Date: Jul 2013
Location: San Diego, CA
Posts: 3,157
Re: Solar Panel efficiency - Should I upgrade

Quote:
Originally Posted by newhaul View Post
Sorry forgot we are running 2x 100 watt mono panels with a pwm controller IMO not worth the cost of mppt for our needs
That's really good for a PWM controller! With 200w into an MPPT controller, I wouldn't expect to see over 12.5-13A max, you're right, not worth replacing the controller.

I did find a 20A MPPT controller that sells for $102 delivered. I've installed 5 so far, and they produce very close to calculated output. I have one with 410w on it (too much current, but it produces 22A for almost all of the day, as opposed to the normal daily curve) and 2 have a 205w panel ea and 2 have a 230 watt panel ea. Those are all RV installs, so they use less power than a boat at sea with fridge, autopilot, etc.

Even though these systems were all under 20A, I figured $100 was worth it for an MPPT.
__________________

__________________
socaldmax is offline   Reply With Quote
Old 23-05-2015, 15:22   #33
Registered User

Join Date: Jul 2013
Location: San Diego, CA
Posts: 3,157
Re: Solar Panel efficiency - Should I upgrade

Quote:
Originally Posted by monte View Post
sorry for the confusion, I meant we use 20 Ah continuously, ie 480 A/day
Panels put out around 50 Ah for around 8 hrs/day with the shading and limited November sunlight hours
I think we should be right next passage by cutting back on usage
Monte, with a Lagoon 400, wouldn't it be possible to mount your panels on an arch, with no shade?
__________________
socaldmax is offline   Reply With Quote
Old 23-05-2015, 15:27   #34
Eternal Member
 
monte's Avatar

Cruisers Forum Supporter

Join Date: Jul 2011
Location: Australia
Boat: Lagoon 400
Posts: 3,650
Images: 1
Re: Solar Panel efficiency - Should I upgrade

Yup, but unfortunately the spinnaker tended to shade the panels a lot during our Atlantic crossing. That combined with 50% clouds most days limited the output.Click image for larger version

Name:	ImageUploadedByCruisers Sailing Forum1432416453.612247.jpg
Views:	88
Size:	50.2 KB
ID:	102625
__________________
monte is offline   Reply With Quote
Old 23-05-2015, 15:33   #35
Marine service provider
 
newhaul's Avatar

Cruisers Forum Supporter

Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 4,030
Re: Solar Panel efficiency - Should I upgrade

That's with a 30 amp pwm controller so can add up to 200 watts more
__________________
newhaul is online now   Reply With Quote
Old 23-05-2015, 15:38   #36
Eternal Member
 
monte's Avatar

Cruisers Forum Supporter

Join Date: Jul 2011
Location: Australia
Boat: Lagoon 400
Posts: 3,650
Images: 1
Re: Solar Panel efficiency - Should I upgrade

Efficiency of these panels is around 18% from memory
Click image for larger version

Name:	ImageUploadedByCruisers Sailing Forum1432417125.997732.jpg
Views:	96
Size:	62.9 KB
ID:	102626
__________________
monte is offline   Reply With Quote
Old 23-05-2015, 15:41   #37
Registered User

Join Date: Mar 2014
Posts: 81
Re: Solar Panel efficiency - Should I upgrade

Don't know which victron blue solar mppt controller you have but there is a know software issue with some, my 75/50 is producing around a third of the expected amps to the batteries, Victron are replacing it under warrenty.

Regards

Ab


Sent from my iPad using Cruisers Sailing Forum
__________________
Abgreenbank is offline   Reply With Quote
Old 23-05-2015, 15:49   #38
Registered User
 
Capt Gill's Avatar

Join Date: Dec 2008
Location: Horseshoe Cove Sausalito/Currently in La Paz,BCS,Mex.
Boat: Ron Holland 43 Semi-custom Sloop
Posts: 118
Re: Solar Panel efficiency - Should I upgrade

Keep in mind when calculating the amount of power (watts) to not use the vendor's power rating as most use open circuit voltage which you cannot use to charge your batteries, it's more like 14.2 v , so the arithmetic (not math) is more like: 14.2 X x amps = x watts. I've found the useable power to be about 80% of what is advertised. So far I've only found Ocean Planet to state power ratings realistically, if there are others I'd like to know.
__________________
Capt Gill is online now   Reply With Quote
Old 23-05-2015, 21:22   #39
Registered User

Join Date: Jul 2013
Location: San Diego, CA
Posts: 3,157
Re: Solar Panel efficiency - Should I upgrade

Quote:
Originally Posted by Capt Gill View Post
Keep in mind when calculating the amount of power (watts) to not use the vendor's power rating as most use open circuit voltage which you cannot use to charge your batteries, it's more like 14.2 v , so the arithmetic (not math) is more like: 14.2 X x amps = x watts. I've found the useable power to be about 80% of what is advertised. So far I've only found Ocean Planet to state power ratings realistically, if there are others I'd like to know.
I'm a little confused.

Which vendors? Solar panel or controller? All of my solar panels (4 different brands) all used Vmp for their output calculations, not Voc. Of all of the brands of solar panels I've looked up, all of them have used Vmp, not Voc, to calculate wattage. The main thing I use Voc for is to ensure I don't exceed the max input voltage of the solar controller, either in series or parallel.

Can you give a specific example of this? My 20A solar controller has a max PV wattage of 300w, which comes out to 20 A output @ 15v, not 14.2v.
__________________
socaldmax is offline   Reply With Quote
Old 24-05-2015, 03:35   #40
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,619
Re: Solar Panel efficiency - Should I upgrade

There is some confusion about solar panel ratings.

The good news is that all the solar panel companies measure the output under identical conditions, (STC) so the results can be compared. The wattage is always Vmp x Imp. The bad news is that these conditions are not very representative of average conditions. The panels are measured for this test with very bright flashes of light so the solar cells never get at chance to heat up.

Some panels list the NOCT output, which is more realistic of real world conditions. Unfortunately, fewer manufacturers are listing the results of this test so it usually not possible to use it when comparing panels.

However the solar panel statistics contain a wealth of information. They always list the temperature coefficients for Vmp and Imp so you can calculate the output of various panels in real world temperatures. Some list the output at different luminances. If this is available you can calculate the output under a range of conditions.

The listed STC wattage of the panels will be rarely seen in practice, but you should occasionally see the panels producing this output under ideal conditions with a MPPT controller. This is a good test of healthy well installed system. However, do not rely on the solar panel display for this test. These displays are typically optimistic. Use your battery monitor or better still an accurate multimeter.

If you have a non MPPT controller you should occasionally, under ideal conditions, see an output equal or slightly greater than the sum total of the Imp.
__________________
noelex 77 is offline   Reply With Quote
Old 24-05-2015, 05:31   #41
Don't ask if you can't handle it
 
sailorboy1's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: On the boat somewhere
Boat: Hunter 410
Posts: 12,320
Re: Solar Panel efficiency - Should I upgrade

Some impressive power usage and supply being quoted in the thread . Meanwhile its 715am and I'm getting 6.2 amps out of 290 watt panel into my little 460ah bank that is at 92% for running the frig last night


Sent from my iPhone using Cruisers Sailing Forum
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is offline   Reply With Quote
Old 24-05-2015, 05:47   #42
Registered User

Join Date: Dec 2013
Location: Rogoznica, Croatia
Boat: Bavaria Cruiser 40
Posts: 620
Images: 16
Re: Solar Panel efficiency - Should I upgrade

Quote:
Originally Posted by sailorboy1 View Post
Some impressive power usage and supply being quoted in the thread . Meanwhile its 715am and I'm getting 6.2 amps out of 290 watt panel into my little 460ah bank that is at 92% for running the frig last night


Sent from my iPhone using Cruisers Sailing Forum
Just checked the input from my ickle 35w flexible panel, currently lying on the coachroof, in front of the spray hood, at completely the wrong angle to the midday sun, with 1 section shaded by the boom and I'm showing 0.9amps. Now the battery is fully charged as I'm in my home marina and have been on mains all month so it's possible the panel could be capable of supplying a little more but the charge control must be kicking in. So I am going to leave it on battery for a couple of hours and see what I get.

Keiron
__________________
kas_1611 is offline   Reply With Quote
Old 24-05-2015, 06:39   #43
Registered User

Join Date: Dec 2013
Location: Rogoznica, Croatia
Boat: Bavaria Cruiser 40
Posts: 620
Images: 16
Re: Solar Panel efficiency - Should I upgrade

OK, fridge has kicked in and pulled out a few amps and now the same 35w flexible panel, still shaded by the boom, is valiantly putting 1.2amps back in.

Given it is 14:35 CEST and I am at 4331'N, air temp is 23C (shade) and the panel is flat on the roof rather than angled towards the sun (so not an ideal angle of incidence) that's not bad, it works out as 50% of theoretical maximum (35w/14.2v=2.46amps).

Keiron
__________________
kas_1611 is offline   Reply With Quote
Old 24-05-2015, 07:41   #44
Registered User
 
brownoarsman's Avatar

Join Date: Nov 2008
Location: Round Bay, Severn River
Boat: Formerly Pearson 28-1, now just a sailing dinghy
Posts: 1,320
Re: Solar Panel efficiency - Should I upgrade

This is as good a place as any to ask a question that's been bugging me I guess!
I've spent hours reading solar panel threads and websites, and obviously shade is bad, but how much shade is how bad?
Is the shadow of a spinnaker halyard going to drastically cut your solar efficiency? Or does it only start to matter when whole cells are shaded? The Internet suggests that getting shades across the short dimension is the worst due to how the panels are constructed (series run lengthwise, so shade on the short horizontal axis disrupts all the series). But would there ever be an argument to use a smaller 45w panel over a 100w panel if the 45w panel can be kept in full sun and the 100w panel would be partially shaded?


Sent from my iPhone using Cruisers Sailing Forum
__________________
brownoarsman is offline   Reply With Quote
Old 24-05-2015, 08:12   #45
Registered User
 
tstano's Avatar

Join Date: Mar 2012
Location: NH
Boat: Pearson 530
Posts: 98
Re: Solar Panel efficiency - Should I upgrade

Your problem is that it's not noon 24 hours a day. Too many variables like temp, humidity, battery condition, cloudiness, and a moving base. I'm pretty sure they test panels in the desert aimed directly at the sun at a certain temp. The Peukert effect on how well your batteries take the charge may also have come into play. What was your SOC during your observations? Lot of good info by previous posters.
__________________

__________________
All U Get
tstano is offline   Reply With Quote
Reply

Tags
enc, solar

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Solar panel efficiency Orchidius Electrical: Batteries, Generators & Solar 20 19-03-2014 15:24
News: How to Make the Most of Solar Power (Increase Your Panel Efficiency) E-P Electrical: Batteries, Generators & Solar 3 12-08-2010 23:59



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 14:58.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.