Solar Panel Advice

P

Peter_BDA

New member
Hey folks, quick question regarding solar panels etc.

I bought a 5W SunForce trickle charger solar panel and the instructions (yes, I read them!) say to disconnect from the battery before starting engine. I did not buy the 7W charging monitor etc.

I am assuming that this is to prevent damage to the panel from power back feeding to the panel when the engine is running and the batteries are charging?

I was planning on hard wiring the solar panel to my house battery but this is making me reconsider (I guess I could put a switch in the positive lead).

Any advice???

Peter
 
You need a diode to avoid any current damage to your panel. This should already be installed in your panel controller if you have one
 
OK so I need the controller to be on the safe side form the sound of it.

I also need help painting the boat bottom if any one want to "drop by" :D
 
Get yourself a little morningstar sunguard unit and wire that into your system. Then you can even add more panels in the future and let the solid state weatherproof unit handle the connection for you.
 
I have used this size and the smaller one on my RV and boats when I left them in Calif or Las Vegas. The batteries were always fully topped off even if I had not run the engine for over 6 months. I would opt for the controller, if you are going to hard wire it in place. In my situation, the first thing I did after removing the cover was to disconnect the solar panel.
 
Peter, I have always wanted to practice bottom painting a C-Dory :roll: Do you have a place by the beach :P :lol: I can be there in about 2 days, and it might take me a while, only a month or so to get it right :roll: :wink Oh yikes, Do you have hurricanes there :?: Oh oh, I'm allergic :oops:

Harvey
SleepyC :moon
 
Hurricanes are just another excuse to drink rum!!! After having 30' plus boats in the past I am actually looking forward to painting a "small" boat. :)

Solar Panel Update: Sunforce emailed me back and said that there is no electrical reason NOT to hard wire the panel. The warning is more to prevent the solar panel flying around a moving vehicle-so more of an "idiot insurance warning" (my words not theirs!!).

Peter
 
OK, I just replaced my marginal HQRP 7A charge controller with a 10A Sunforce controller. It has a digital display of battery voltage which is nice. Here's the issue: Connections are simple and made correctly, 17+ volts coming out of our 20W monocrystalline panel. Controller shows both input from panel and that charging is taking place. Cuts in at 13.3V and out at 14.42V. With a 120V 10A charger connected the batteries (2 brand new gp24 deep cycle in parallel) go to 14.5V. As soon as I remove the 120V charger from the circuit leaving the solar system connected, the battery voltage starts dropping and goes down to 12.54. It is dropping with the solar panel connected and providing 17+ volts. To me this looks like I have a parasitic load somewhere in the system. Am I correct? And...now to find and fix this I have to remove every single load (circuit) one by one until I find the culprit. Correct? Advice from those with more knowledge than I is very welcome.
 
I would disconnect all loads to the battery first and see what the voltage is. The first question I would ask was the battery fully charged on the charger?

With the charger on and the voltage at 14.5 volts, means that the battery was not fully charged, and the charger was in Bulk or Absorption phase. When the battery is fully charged--you will go into float stage. There the battery voltage will be somewhere in the 13.3 +/- range.

The smaller deep cycle batteries are not the true deep cycle, like a Rolls, or the L 16 traction batteries. These have much thicker lead plates. The voltage you are reading when just finished charge, is going to be a surface plate voltage, slightly higher than the true voltage of the battery. When you first pull it off the charger in float phase, the battery voltage will be 13.1, and gradually drop down over time to 12.6 to 12.7.

I would also check the battery voltage with a good digital volt meter. Although unlikely, the voltage you are reading off the controller, might be a little off. The controller does several things, but one is to prevent back feeding of the solar cells at night, or when in low light.

The 17+ volts is normal for the solar panels. They are relatively low output, and thus the voltage has to run higher, to "push" electrons into the plates (simplistic explanation). The controller keeps the battery from being overcharged when it is full, and the controller has gone into float stage.
 
Thanks Bob. I do check the battery voltage with a digital voltmeter. Yes, the batteries are not true deep cycle, they are the hybrids. The controller is accurate to 1/100th of a vollt. I am charging with the Bepp management system in the off position thus the two batteries should be electrically isolated from everything else. I can disconnect them from everything manually but right now will trust the Bepp VSR system. Right now I have the 120V charger on until it shows fully charged, that takes a while with 10A and the two batteries in parallel.
 
Barry, when are you reading 17v? With the solar cells in service or off line?

The actions of electricity (volts/amps) is less mysterious if we equate it to the similar action of water in a hose (pressure/flow). If you take the voltage reading that a solar cell is producing (off line) and it is 17v that is like measuring the pressure of water in a hose with the tap closed. When that cell is put into service - especially if it is connected to a battery that is not fully charged - the voltage will drop close to the nominal (at rest) voltage of the battery - before slowly building. When the amps have a place to go (load applied) it is like opening the water tap - once water starts flowing the pressure immediately drops. This does not mean it isn't charging - if it did send your battery voltage up to 17v then you would have a problem!

Like Bob said , a small solar cell like some of us have on our boats does not put out a lot of current. Even in full sunlight and no load on the battery voltage will rise painfully slow - especially if your watching :lol: The Trace invertor that charges my off grid system puts out 150amps during the bulk charge stage - it still takes over an hour to bring the bank up to its absorption stage voltage (14.6).

Regards, Rob
 
Barry,
I went back and you had posted on another thread last year about this solar panel and batteries. My concern is: 1 20 amps is going to be at theoretical max output for that solar panel--It is measured at 17.1 volts (output of the solar panel, not the 12 or 12.5 volts), 90 degrees sunlight, on a clear day, ambient temp at 20* C, etc. On an average you would be lucky to get 0.8amp to the two batteries under ideal conditions. There are various types of controllers--and the Maximum Power Point Tracking (MPPT) increases the current by lowering the panel's output voltage, which increases the charging amps to the battery by up to 19% (but I doubt if this controller is a MPPT type). Bob's excellent analogy with water holds here. The prices for an MPPT controller vary all over, but the better ones are relatively expensive.

2. I am not certain about your BEP VSR, but many VSR do have a parasitic drain. There can be a number of parasitic drains on the boat--with radios, Some GPS, stereo etc.

3. No free lunch; The the brochure from your controller: Current Consumption when connected 12V Array (Battery not present) 55 milliamps, and Current Consumption when connected 12V battery (Array not present) 10 milliamps. I don't know if this includes the LED draw, but suspect it does. Then there is some (small) current consumption from the LCD panel which displays voltage. Granted that these are very small, but they can still add up.

I probably would put the high amperage (10 amps) circuit of your volt meter in series (with alligator clips which fit on the ends of the probes), and then measure current from the solar panel into the battery after the new controller. (If you verify it is less than 1 amp, then go to milliamp scale, with the probes in the "normal" place. Then I would measure the output of the battery (after fully charged), between the positive terminal and the BEP controller--and work down the line from there looking for an amp thief in parasitic drain. You might want to confirm the controller draw--which may be less than stated in the brochure.

When you get down to precise voltages, I am not sure how accurate the volt meter on your controller is. I certainly would rely on a $12,000 Fluke 8508A 8.5 Digit Reference Multimeter, than a "Sperry" for $19, or the LCD volt meter on the controller (which you can buy for 84 cents --probably less for the manufacturer of the controller). These give relative voltages, but may not be precisely accurate. If you have a bench Fluke you have compared it against--then believe it! The "cheap" Digital multimeters are great--they are not always precisely accurate.
 
Bob,

Thanks for the reply. My previous post was about issues with another controller, since replaced, and two older house batteries, since replaced. We'll see how it looks tomorrow.
 
Barry, I will leave the technical analysis to others, but as you know, we have two 100 watt solar panels on Daydream. I had no idea what was actually going on with the panels and my batteries until I installed the Victron Battery Monitor. This tracks voltage, state of charge (SOC) as a percentage of fully charged, amps flowing (in or out), and amp hours used. With 200 watts, there is a theoretical ~11 amps of current that might be going into the batteries (200 watts / 17 volts). In bright sunlight we saw a maximum of about 4-5 amps flowing in. In less favorable conditions it was frequently around 1 amp. When the ARB freezer cycled on, the amps dropped (netting out production against load) and in cloudy conditions usually went negative - the freezer was drawing more amps than the solar panels were producing. So I would not expect too much from a 20 watt panel! For us, the upside was that with brigh sunshine, the SOC charge recovereded fairly quickly, about 4 hours, even when we had consumed 20 amp hours overnight. So we think we are ready for Lake Powell!
 
Pat Anderson":450fqxio said:
Barry, I will leave the technical analysis to others, but as you know, we have two 100 watt solar panels on Daydream. I had no idea what was actually going on with the panels and my batteries until I installed the Victron Battery Monitor. This tracks voltage, state of charge (SOC) as a percentage of fully charged, amps flowing (in or out), and amp hours used. With 200 watts, there is a theoretical ~11 amps of current that might be going into the batteries (200 watts / 17 volts). In bright sunlight we saw a maximum of about 4-5 amps flowing in. In less favorable conditions it was frequently around 1 amp. When the ARB freezer cycled on, the amps dropped (netting out production against load) and in cloudy conditions usually went negative - the freezer was drawing more amps than the solar panels were producing. So I would not expect too much from a 20 watt panel! For us, the upside was that with brigh sunshine, the SOC charge recovereded fairly quickly, about 4 hours, even when we had consumed 20 amp hours overnight. So we think we are ready for Lake Powell!
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Barry

Do you have any photos of your solar setup? I tried looking at your albums, but did not see anything there.

Trying to get an idea of size, cost and complexity.
 
I like the Renogy system. Their prices are much more reasonable than others. I would prefer two 50 watt panels instead of one big 100W panel (i.e. if the 100W was split lengthwise). I think that this would be easier to install on the CD22 given the lack of large open spaces. I would put one panel on each side of the center roof bump (outside the rails). This would leave the center clear to carry stuff. It is unlikely that whatever I carried on top would shade both panels at the same time.
 
OK, charged both batteries to full charge yesterday using 10A 120V charger, cleaned up some old connections. All is well today; good sunlight, the panel is doing as expected, i.e. keeping the house bank up with little or no load. That is its sole function so a small 20W panel is adequate. Dredged up old memories and Ohm's law from more than half a century ago when I taught vacuum tube circuit design, did some calculations and I am happy. Thanks all for your thoughts, advice, and suggestions.
 
Here are our two Renogy 100 watt panels on Daydream. Probably difficult to put on a CD22, you could probably put one on the roof but then where would you put the dinghy or kayaks?

2013_09_03_12_51_32_HDR.sized.jpg

ssobol":or702fht said:
I like the Renogy system. Their prices are much more reasonable than others. I would prefer two 50 watt panels instead of one big 100W panel (i.e. if the 100W was split lengthwise). I think that this would be easier to install on the CD22 given the lack of large open spaces. I would put one panel on each side of the center roof bump (outside the rails). This would leave the center clear to carry stuff. It is unlikely that whatever I carried on top would shade both panels at the same time.
Click to expand...
 
Barry,
What is the voltage with the solar panel in full sun--and then see what it does during the night. Inquiring minds want to know.

Thanks,

Bob
 
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