Power from Solar + Measuring Energy Balance

[b_rodwell]

I am having difficulty living using only solar power while on anchor. I have 2 questions.

Expected Power from Panels

I have 8 x 120 watt HP-flex panels. Should be 960 watts. The panels are mounter horizontally at the back of the boat where there is little shading. I have an Outback controller. I am in the Balearics and on a sunny day with low haze the best power I have seen is 40 amps at 14.1 volts output. This is 564 watts. Is it normal to have this sort of discrepancy between the advertised power and the observed power?

Measuring Consumption

Measuring the power in from the panels is pretty easy. It is displayed on the controller. I have been recording the amps and volts each hour. Measuring the electrical consumption is a little harder and I am seeking advice on this. I am trying to measure the amp/hours of 2 fridges and 1 freezer. I believe these will be the key power consumers.

• The electrical board (I think) shows net amps from everything. It is difficult to determine the load from one appliance.
• The fridge and freezer loads are intermittent
• Is there an instrument that measures amp/hours?
• Any other clues on how to make these measurements?
• How do you find the cables from the fridges and freezer to make the measurements? The boat is a Lagoon 400.

Lastly do other Lagoon (400) owners with solar panels have a similar problem. The boat has no genset.

Thanks
Brian

[rooiedirk]

[QUOTE=b_rodwell;1867473 The panels are mounter horizontally at the back of the boat where there is little shading.[/QUOTE]
The rated power form manufacturer is given for the panel tilted 90 degr towards the sun. Depending of your latitude and the suns declination, the max power generated is always (much) less then rated.
Rougly the max. output (when the sun reaches is highes point) should be equil: ratedPower x cos( lat. - decl )

Apart from above even a little shading will drop performance dramaticly.

[noelex 77]

Originally Posted by b_rodwell

I have 8 x 120 watt HP-flex panels. Should be 960 watts. The panels are mounter horizontally at the back of the boat where there is little shading. I have an Outback controller. I am in the Balearics and on a sunny day with low haze the best power I have seen is 40 amps at 14.1 volts output. This is 564 watts. Is it normal to have this sort of discrepancy between the advertised power and the observed power?

I think something is wrong with some of panels or the wiring etc. Your peak production is less than 60% of the panel rating. On good days where there is no shadow over the panels you should be at least occasionally seeing 85%+.

I have just had a look at my meter and as I type we are putting out 88%. 290W from 330w of panels. There is nothing exceptional about this, just a snapshot. (Edit just checked again and the recorded peak today is now 310w (94%). The peak sun angle is due in 15 mins.) These are the sort of numbers you should be seeing if your system is working well and the panels are in full sun.

On the best occasions when the sun just peaks out we have (just) exceeded the panels output rating. With a healthy system, in area of high insolation you should be doing the same.

The first step in diagnosing the problem is to measure the output from each panel. A clamp on multimeter will do this easily. You don't need to break any connections, although you do need to get at a single (+ or -) wire from each panel.

[monte]

Hi Brian and Lorraine
I assume your controller is rated for more than 40A? 40 does seem a bit low for your system in full Balearics sunshine, but still that should equate to ample per day at anchor. The best way to check appliance usage is process of elimination. Turn of the fridge when it's running and compare the amp usage on the panel. Do it a few times to get an average, but it's likely to be around 5Ah per fridge for around half the time, so a total of 120A per day for two fridges. Do the same with the laptops and iPad, they consume quite a bit when charging. Lights hardly use any. I think the 3 cockpit LEDs use about 1Ah. Check the WM consumption as well.
One issue can be sulphated batteries. It helps to equalise them every couple of months, but you need to be on shore power for that. Also the battery monitor at the panel is very good, but % of charge can't really be trusted after a couple of months off shore power. When it shows 100% it may actually be quite a bit less. When it does show 100%, keep an eye on the amps going in. They should drop back to a lot less than the solar is putting out, around 10A as the batteries acceptance rate falls. The solar controller also should be set up properly for the batteries. I think our setting is 14.8A for 12 hrs bulk stage, then 14.4 for absorption and 13.5 for float. We have the exide duel batteries, I'm not sure if you have the same. These batteries have much higher settings than normal lead acid and also higher SOC voltages. We often see less than 12.5 V first thing in the morning, before charging resumes so you might want to adjust your battery alarm level, or turn it off. This is pretty normal as the batteries are being used overnight for refrigeration and doesn't really reflect the rested state of charge, which would be higher.
When you say the solar is struggling to keep up, what are your reasons for thinking that? The monitor isn't getting up to 100% or bulk voltage? Or alarms are going off in the early hours? Our BM tends to cycle between 85% and 100%. Also how many and what type batteries do you have? Adding another battery or two might help get through the night if you just have 3/140Ah batteries.

[Captain Bill]

I am assuming you are seeing 40 amps @14.1V going into your batteries, not coming from the solar panels. With an mppt controller the voltage on the panels should be a bit higher. At 14.1 volts lead acid batteries are getting pretty close to fully charged and they simply won't take full amperage. I only see full amperage into my batteries when they are below 80%. How big is your battery bank and what voltage is the controller set to for acceptance mode? Also, 960 watts translates to a lot of amps at a nominal 12 volts. Is your cabling from your panels to the controller large enough to handle that much power? If the length of the cable is long enough you might need as big as 0 awg cable to avoid significant losses.

[hamburking]

It sounds like you have a bad panel. At least one.

[Trim50]

In order to help you here, I need answers to some questions...

1) How do you have your panels wired? ie, many panels are parallel and how many in series?
2) What is the max voltage going into your controller?
3) What Outback controller do you have 60 or 80?

4)What type of batteries do you have and how much capacity do you have?
5)How are they wired?

Having a balance between battery capacity and solar capacity is very important and something most people have no clue about. If your batteries can't accept the energy being sent to them, the controller simply produces heat from that excess energy.

I have 4 x 200W Trina Solar High-Efficiency Monocrystalline panels mounted flat. They are wired in two parallel strings to keep the voltage below the limit of the Outback 80.

On a best condition day at the equator with the boat pointing just right and minimal shadows, I produce 250Amp-hrs per day while making water with my 30GPH DC watermaker. The watermaker is important because it keeps the battery voltage below 14V while the panels are pumping the max power. As such, I can make 200 gallons of fresh water while also keeping my ice cream frozen and beer cold.

Also, I have 16x6V Trojans...so lots of capacity to accept that solar energy.

I think your 40amps @ 14V with flexible solar panels is reasonable performance based on my experience with panels laying flat.

Expandable 800 Watt Solar Array | S/V Trim

[b_rodwell]

To answer some of the questions:

1. I suspect the panels are wired in parallel because I get about 19v input to the controller.
2. 19 volts
3. It is an Outback but the way it is mounted it is hard to identify the model number. I will send a photo when my camera is charged. I am loath to take it out.
4. The batteries are brand new6 x Fulmen FG1406 @ 140 Ah each = 840 Ah.
5. The batteries are wired in parallel

A photo of the controller is coming soon.

Thanks
Brian

[Captain Bill]

Originally Posted by b_rodwell

To answer some of the questions:

1. I suspect the panels are wired in parallel because I get about 19v input to the controller.
2. 19 volts
3. It is an Outback but the way it is mounted it is hard to identify the model number. I will send a photo when my camera is charged. I am loath to take it out.
4. The batteries are brand new6 x Fulmen FG1406 @ 140 Ah each = 840 Ah.
5. The batteries are wired in parallel

A photo of the controller is coming soon.

Thanks
Brian

I am not familiar with Fulmen FG1406 batteries so I looked them up. They are sold as starting batteries, not deep cycle. I would not count on them lasting long in a house bank.

19V sounds good for the panels. AFAIK Outback only sells two models, the 60 and the 80. Hopefully you have the 80 because you'll be approaching that output if your bank gets depleted and you get your output up to what you would expect. Do you know how long your cable run is and the size of the cable coming from your panels to the controller? Undersized cables are a common cause of solar system under performance.

[meikelvet]

The cheapest way is a digital Multimeter, cost about 10 Euro, with this you can measure the amperes every cooling device is consuming when running(measure between the + and - pol direct on the cooling machine), next thing you have to do is stop the time the machines are running per hour,depends on cabin temperature,how often the doors are openend,filling grade etc. and then you can estimate your Amperehour consumption of your cooling luxury ����, I think that you hardly generate enough only with solar power,
except your whole deck is covered with solar panels ��.
Maybe you must add a windgenerator or a small diesel generator.
Just my 2cents
Meikel

[ddavis4464]

You've received many good responses. I only have a couple ancillary comments. I have eight panels, mounted in two groups, which individually have 18v and 36v outputs. I bundle them, series and parallel as required, to drive the Outback at about 90v, requiring much smaller wiring and affording less line loss. Big wire has big costs these days. The next thought, which was alluded to by someone before me is the charge state of the battery bank. If it is nearly fully charged the 40A draw may represent you draw by the refrigeration system. And not at all reflective of the solar installation. Best of luck.
Danny L. Davis

[Tomaz473]

Originally Posted by monte

Hi Brian and Lorraine
..., but it's likely to be around 5Ah per fridge for around half the time, so a total of 120A per day for two fridges.

Good info. It would be even better if you would get units correctly:
..., but it's likely to be around 5A per fridge for around half the time, so a total of 120Ah per day for two fridges.

[hellosailor]

A "little" shading can still knock out an entire panel. You want to get no shading while you are testing things.


You can test for a bad panel by disconnecting them both, then measure the power from one compared to the power from the other. Both the same? OK, then they are both good.


You can easily test the power used by any one appliance by simply turning them all off. Surely there are breakers or power switches for all of them, so just turn them all off and then turn on just the one you want to measure.


And a quick trip to the Outback web site should show you what the different models are, you don't have to snap & post a picture. You DO want to get into that inaccessible controller and make sure that any dip switches for programming it are set correctly. Also that any other set-up parameters are correct.


That's all a start, then you'll need to start using a multimeter and checking your wiring for perhaps runs of wire that are too long, too thin, or poorly connected as well.


Solar panels lose about 10% of their power for each 15 degrees that they are faced away from the sun. So every hour away from "local noon", you lose another 10% of the potential output. 11am, you'll only get 90%. 10am, you'll get 90% of 90% (i.e. 81%), every hour before or after noon...a ten percent loss. And that's with zero shading or haze.

[newhaul]

We had an issue like that with our hard panels after a perticularly rough water day.
Checked and found that one of our panels had become unplugged. Couldn't tell by looking but just enough to stop the power from leaving the panel. Check all connections manually not just visually.

[ozsailer]

Hi Brian,
some great information has been given so I rehash what has already been said. A couple of things I will raise are the following.

1) It is of great importance to know what power you boat is consuming over a 24 hour period so that you understand the power that is going out as well as coming in IE solar panels/alternator. I would highly recommend going through your boat and itemising all the electrical items you have on your boat, the time that on average they would be used daily and calculate within close proximity your power draw. Don't Cheat its important you work out your worst case scenario IE overnighting extended cruising with everything running such as Auto pilot, nav lights etc. Once you know how much power your boat consumes, and it is surprising, you can start to understand how much power you need to generate to supply those needs. A quick search of google for boat power calculations should find you a spreadsheet to use and make life easier.

2) You note that the best power you have seen being generated by your solar panels is 40 Amps. There could be many reasons you have seen only this amount. If your regulator is wired correctly it will only feed your batteries what they need, same as a car alternator or a battery charger. Example we have 120 AH alternators on our boat but that does not mean they pump in 120 all day long. As the battery charges the amount requires reduces through the regulator till almost nothing when fully charged. Same as the regulator on the solar system. Heavy deleted batteries will take a fuller charge and reduce as they become full.


3) Do you know who did the original installation. If not I would contact Outback suppliers who may be able to assist with how the panels may wired and what you should expect from you system.


4) You stated that you had two fridges and on freezer. They suck the power on any boat. It is probably the main things that consumes power as they would be on 24/7 if you lived on the boat. A) Do you need both fridges and freezer on all the time to assist in power management.

We are currently cruising on our Lagoon 410. I have house batteries rated at 400AH. Our solar panels combined input is 300 watts and I have two 120AH alternators on the motors. This is ample power to keep us cruising. We have a large fridge and freezer and normal electrics. We do power manage but don't go without. From memory I worked out that our power consumption over a 24 hr period was 100 AH or so. In reality we use about 60AH when cruising. Our charging system copes more than adequately. We are in Hervey Bay at the moment on the pick and the solar panels are keeping up with our power usage.
I installed a Vitron Brand battery monitor to assist in keeping an eye on our power consumption and input. I use it as a guide only but to date it reasonably accurate. It displays, voltage, current being used, current being generated, total power used in watts and battery capacity in percentage. It works for us but I do know it has limitations.

Hope this is of some assistance



Greg and Sue
SV Sunshine.