PV output drop

wespo

Hello All,
I am new to this forum, but not very new to solar. I currently have an off grid system using 4x 180 watt Evergreen SL panels connected 2 in series to input about 50 volts to an FM60 charge control to a 440 AH -24 volt AGM battery bank. I live in the tropics at 18 degrees lattitude. Most of the time the system works well and puts about 20-21 amps into the batteries from 10am-2pm according to the Trimetric meter (without the frige running). Today (and 3 times before) I noticed that at high noon, the panels were only putting out 6 amps total. The charge control indicates that the input is 56 volts, but the amp output is only 2.5 - 3 amps (at that voltage...top line of the FM60). I can correct the problem if I cool the panels down with a hose for 3 or 4 minutes...(back to 20 amps)...but the problem returns once they dry and heat up again. Normally I do not see this king of drop, but I am cocerned something is not right with 1 or all of the panels. Any suggestions??? Thanks.

icarus

Re: PV output drop

Can you easily isolate either string, either by unplugging it, or covering it? By doing so, you might begin to isolate if it is a PV problem or a controller problems.

Sounds to my uneducated ear that it is a controller problem.

Tony

FL SUN

Re: PV output drop

Welcome.

You have verified the DOD of the batteries is at a point where they can take a full load charge off the panels? All your connections are sound and tight with no corrosion?

If so, then I'd isolate all four panels, and test them individually to determine an anomaly. Using a DMM, test the Voc of each one, then do the same thing testing your Isc of each panel, noting what you observe on each panel. Of course, all the panels must be at the same plane, and no shading of any cells while doing this. Taking the temperature of the panels in consideration, and using the spec's of the panels in good sun, you should be able to determine if one or more panels is drowning out the others.

wespo

Re: PV output drop

I can easily isolate it, as I have each string on a seperate breaker in the combiner box. When I cut both breakers, the controller correctly reads 0 volts in & 0 amps out. The trimetric reads -2.8 amps. 1 breaker on reads about the same volts (53 -56) and 1/2 the amps (1-2) on the FM60. The trimetric reads about 3.5 - 4 amps. The same happens with the opposite breaker on. if I spray the panels with water the FM60 will read about 44-47 volts and 11-13 amps (top line) and the trimetric will read about 20 amps. This is only the 3rd or 4th time this has happened in a couple of years. Normally the output is steady...even with direct sun on a hot day.
Thanks.
Bill

jeffkruse

Re: PV output drop

Are you in the Caribbean? Is the Sahara dust thick. I live in Puerto Rico and the last couple of months have seen afew realy hazy days due to the dust. My output was cut by more than half.

Solar Guppy

Re: PV output drop

On the current FM series I have observed tracking issues. What I have seen when it does a sweep, it gets stuck at the wrong voltage and stays there sometimes for hours.

Cooling panels will make a rapid change in the Voltage that likely has the controller do a re-sweep.

One thing you can do, is go into the menu and change to manual mppt mode when this happens. Run ~ 70% , if the power comes back you have confirmed it the units tracking is the cause and not your panels.

crewzer

Re: PV output drop

wespo,

There have been some reports of FM controllers getting "stuck". You may need to contact OutBack Customer Service and request a firmware update.

HTH,
Jim / crewzer

Solar Guppy

Re: PV output drop

Jim, is there an update since I last sent you a PM a few months ago?

wespo

Re: PV output drop

Hello All,
Yes, I do live in the caribbean....western tip of PR. The Saharan air layer (SAL) has been thick and I have observed the same changes of output on those days...about 30% reduction 20amps to 12-14amps. Yesterday I checked each panel as recommended by FL Sun and each panel produced about the same voltage and amperage disconnected. It was cloudy by the time I was able to check them, but they were all producing similiarly...no outliers. This morning, the system seems to be back to normal. Next time this happens I will change the mode in the FM ( not sure how to do this...is it in the manual?) to see if it self corrects. If I do contact Outback to request an update...is this something I can install/perform myself??
Thanks again.
Bill
PS: I also notice occasionally when the FM60 goes into float mode that the voltage and amps will swing between 0 and full panel output. My float voltage is set at 27.2. Generally the controller will hold it at that float voltage, but occasionally I see these swings when it attempts to go into float. Is that normal??
Thanks.

crewzer

Re: PV output drop

Jim, is there an update since I last sent you a PM a few months ago?

Henry,

Yes... AFAIK, firmware rev 002.00.000 is now the production version and is available as an update to "older" models. This is the f/w rev I have in my FM80.

Regards,
Jim / crewzer

halfcrazy

Re: PV output drop

Does that firmware version fix the staying awake at night?

crewzer

Re: PV output drop

I believe so.

Regards, and signing off for a while,
Jim / crewzer

Brock

Re: PV output drop

Just confirming this, but you said when the output amperage was low the solar panel voltage on the controller was 56v? Then after you cooled the panels off it settled in to about 44-47?

The thing that strikes me is when the panels are warmer the voltage should be lower not higher. When they are cooled off with water and running 44-47 that sounds more reasonable. I would guess you should be about 40 when the panels are really warm.

One thing you can try without messing with any settings is if it happens again (or any time really) is to push and hold the far right or the second from the far right button. That should manually let you raise or lower that input voltage. If you can adjust it back down to 40 or so, just watch the amps and set it at the highest output.

It should be doing this itself with a sweep, but as Jim and SG said it could be stuck, this would verify that.

wespo

Re: PV output drop

Hi Brock,
Yes, the reading on the FM60 will read about 55-56 volts when it gets "stuck". I couldn't figure it out either. I did speak with Outback and here is what they said:
1. You can send it in for a firmware upgrade (poor option for me)..or
2. Go into the advanced mode and change the Mode setting to 1 or 2 (these setting make the panel do a sweep every 1.5 hours in different charging modes)

I changed the advanced mode setting to #1 (instead of the preset 0), and that has seemed to take care of the problem. Outback said that the firmware update basically does what I did manually (change the MODE setting to sweep every 1.5 hours). The only problem with this is that the controller shuts down for a minute to do the sweep, so you lose a little power production.

Has there been issues with the unit "staying awake" at night???
Thanks.
Bill