We've had solar panels on our boat since we purchased it, but I'm only now looking at them more closely. We have 2 100 W panels in parallel, which by my calculations should be able to provide up to about 15 amps or so of power in ideal conditions. However, I never seem to be able to get any more than about 3 amps at any time in strong direct sunlight. Am I mistaken in my understanding, or is there something wrong with my system?
Expectations from solar
- Thread starter Adamsson
- Start date
Welcome to SBO.
First question, how are you measuring the current produced?
Where is the current being measured? At the controller or on the system?
What type of panels do you have and where are they located?
What kind of controller and what brand?
Does each panel have its own controller?
Each panel in full sunlight can be expected to produce about 8 amps, so your estimate of 15 amps is about correct. Over the course of the day the panels can be expected to produce about 3 to 4 times the nominal capacity, or 600 to 800 watt hours.
The biggest culprit in reduced solar production is shading. Depending on the placement and quality of the panels. Higher quality panels are more immune to shading, less expensive panels are more subject to shading effects.
If you are using the system ammeter to measure production what you are really measuring is the net current returning to the battery; current produced less the current being consumed by any devices that are turned on = net current to the battery.
Poor connections can also cause a reduction in current reaching the battery.
Fill us in with some more information and we'll help you find the problem.
First question, how are you measuring the current produced?
Where is the current being measured? At the controller or on the system?
What type of panels do you have and where are they located?
What kind of controller and what brand?
Does each panel have its own controller?
Each panel in full sunlight can be expected to produce about 8 amps, so your estimate of 15 amps is about correct. Over the course of the day the panels can be expected to produce about 3 to 4 times the nominal capacity, or 600 to 800 watt hours.
The biggest culprit in reduced solar production is shading. Depending on the placement and quality of the panels. Higher quality panels are more immune to shading, less expensive panels are more subject to shading effects.
If you are using the system ammeter to measure production what you are really measuring is the net current returning to the battery; current produced less the current being consumed by any devices that are turned on = net current to the battery.
Poor connections can also cause a reduction in current reaching the battery.
Fill us in with some more information and we'll help you find the problem.
Thanks. These panels are set up where they are not shaded as they are above the cockpit, so that is not an issue. The noted 3A is the best I ever see coming from them, and it's usually less than that.
This is what I see on the regulator. It is set up that the positive wire from the panels runs to the regulator. From there, it goes through a toggle switch (to turn the juice on/off). Then to a battery switch, then directly to the battery. The negative is grounded.
The solar panels are from Sharp. The regulator is CMP24 Solar Regulator.
On my battery monitor, it is showing a net draw (we have refrigeration). But if I shut off the refrigeration and other draws on the battery, I get a net increase in line with what I see on the solar regulator.
I should note that this system is almost 20 years old.
This is what I see on the regulator. It is set up that the positive wire from the panels runs to the regulator. From there, it goes through a toggle switch (to turn the juice on/off). Then to a battery switch, then directly to the battery. The negative is grounded.
The solar panels are from Sharp. The regulator is CMP24 Solar Regulator.
On my battery monitor, it is showing a net draw (we have refrigeration). But if I shut off the refrigeration and other draws on the battery, I get a net increase in line with what I see on the solar regulator.
I should note that this system is almost 20 years old.
What type and size batteries do you have? Are they flooded lead acid? AGM? Are they in good condition? The battery type and state of charge will determine the charge acceptance rate. AGM will except a charge faster than flooded lead acid, lithium faster than AGM. A flooded lead acid battery 80% or more charged will severely reduce the rate (amps) of power it can accept.
Also, that charge controller you are using is of questionable quality. You should look into MPPT charge controllers made by known brands that have good reviews.
One other note: there is no need for a switch between the charge controller and the batteries. Most charge controllers are installed by first connecting the controller to the batteries, and then to the solar panels. There should be a fuse between the solar panels and the charge controller, and between the charge controller and the batteries. No power switch is needed because the charge controller will limit or turn off the power to the batteries when fully charged.
Also, that charge controller you are using is of questionable quality. You should look into MPPT charge controllers made by known brands that have good reviews.
One other note: there is no need for a switch between the charge controller and the batteries. Most charge controllers are installed by first connecting the controller to the batteries, and then to the solar panels. There should be a fuse between the solar panels and the charge controller, and between the charge controller and the batteries. No power switch is needed because the charge controller will limit or turn off the power to the batteries when fully charged.
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What is the SOC of your battery bank? If it's full NO charging source will put out much of anything; Basic Battery Charging 101.
True, and most solar systems require you to disconnect the panels before the controller; you risk killing the controller if you disconnect it first.
A lot has changed in 20 years. Panels do have a life span, I wonder if. yours are reaching EOL.
Here's a good article on solar by Nigel Calder.
www.proboat.com
As others have said, battery SOC will affect the amount of current being produced, the higher SOC the lower the accepted current.
No fuse is needed between the panels and the controller because the panels are a current limited device. Thus, you can use wire that is large enough to safely carry the current. A fuse or circuit breaker is necessary between the controller and the battery or DC+ bus because the battery is an unregulated power source and it is possible for a short to cause the wires to carry more than their rated capacity. The fuse/cb size should match the wire size.
No switch is needed between the panels and controller. If you want to turn off the panels, throw a blanket or towel over the panel or wait until dark.
You mentioned the panels are over the cockpit, are they "flexible" panels? Flexible panels have a shorter life span than rigid panels because they will flex and the internal connections can break.
Here's a good article on solar by Nigel Calder.
Advances in Onboard Solar - Professional BoatBuilder Magazine
Advances in onboard marine solar technology improved efficiency and lowered the cost. But they also introduced more complexity.
www.proboat.com
As others have said, battery SOC will affect the amount of current being produced, the higher SOC the lower the accepted current.
No fuse is needed between the panels and the controller because the panels are a current limited device. Thus, you can use wire that is large enough to safely carry the current. A fuse or circuit breaker is necessary between the controller and the battery or DC+ bus because the battery is an unregulated power source and it is possible for a short to cause the wires to carry more than their rated capacity. The fuse/cb size should match the wire size.
No switch is needed between the panels and controller. If you want to turn off the panels, throw a blanket or towel over the panel or wait until dark.
You mentioned the panels are over the cockpit, are they "flexible" panels? Flexible panels have a shorter life span than rigid panels because they will flex and the internal connections can break.
That CMP24 charge controller doesn't look like a very good unit. Check out the Victron line of MPPT charge controllers.
I was quite recently in Nova Scotia and my solar panel produced very well there. My panel is a bit over 1 month old so quite new.
As others have suggested, the system you have is quite likely at end of life. The solar panel construction technology is substantially better today than when those panels were built. The controller technology likewise.
So it depends upon what you need. If you feel you need more power output, time to upgrade your system. If you do not need it, then your wallet will be happier waiting...
dj
As others have suggested, the system you have is quite likely at end of life. The solar panel construction technology is substantially better today than when those panels were built. The controller technology likewise.
So it depends upon what you need. If you feel you need more power output, time to upgrade your system. If you do not need it, then your wallet will be happier waiting...
dj
Thanks everyone. Both the battery bank and the solar panels are on the older side. the batteries are 13 years old (4 X 6V), but they do still accept charge at a much higher rate from the alternator. The solar panels are approaching 20 years. They are rigid panels, but most replies are suggesting that the age of the panels, along with a lower quality controller, could be the culprit. New batteries are on the shopping list for next spring, and I think new panels aren't far behind - I'll add in a new controller to the list.
For your solar system, that would be first on my list. See how well those original panels work with a new controller. Controller technology is so far advanced from your current controller it may be all you actually need. Your original panels may simply be less efficient than current panels. Easy enough to change panels if they are found to be notably below desired output...
dj
this study suggests you prolly have much life left in the panels doing their job.
just saying
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Batteries near EOL can have "normal" voltages and charge acceptance rates. By the time the charge acceptance rate is 0, the cells have died.
What does happen is the battery capacity declines and it accepts a lower overall amount of amp hours. At 13 years your batteries no longer have a ~110 ah capacity, they are more likely to have maybe 50 ah or so. That will reduce the acceptance rate proportionally, the battery is functionally much smaller. So a 10% acceptance rate for a new battery is 11 amps, for the old battery it will be 5 amps.
20 years old? Replace the system with up to date technology, panels, controller and wiring.
Easy with lots of budget. But if I was on a low budget it would be batteries first, controller second and then see how it runs.
dj
You can replace with like size panels and a large controller for about $300. New batteries will cost way more than that and won’t increase the solar system total output.