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B RAD · 10-22-2022, 01:24 PM

I have one 100 amp solar panel connected to a charge controller. It worked fine all summer but now the controller is indicating a low voltage from the panel and batterys are not charging. I went up on the roof of my camper and checked that I was getting 18 volts out of the panel in a morning sun. disconnected my controller and then connected another one that I had. Still same problem, checked wires before they enter the controller and had no power, went back on roof and now no voltage right at panel. Question. Can a solar panel work intermittently when getting good sun or could I have damaged them somehow while disconnecting the controller. I have a hard time thinking both controllers could be bad but I don’t see how the panel could be bad either. I know the wiring is correct with know breaks from controller to panel or battery. I plan on removing the panel from my roof tomorrow so I can bring it home and play around and try to figure out what is going on. Any ideas appreciated.

IAlreadyGot1 · 10-22-2022, 01:43 PM

I bet you have a 100 watt panel.

Voltage at the panel and no voltage at the CC indicate a problem with the wires between the panel and CC. A CC won’t work without input voltage.

What voltage are you reading from the batteries? Their voltage could be too low to allow the CC to charge.

B RAD · 10-22-2022, 02:47 PM

Quote:

Originally Posted by IAlreadyGot1

I bet you have a 100 watt panel.

Voltage at the panel and no voltage at the CC indicate a problem with the wires between the panel and CC. A CC won’t work without input voltage.

What voltage are you reading from the batteries? Their voltage could be too low to allow the CC to charge.

My mistake, yes it is a 100 watt panel. Voltage where the two short wires leave the panel showed 18 volts the first time I checked them and the wires just before they enter the controller also showed 18 volts but once hooked to the controller it still had a solid green PV light which is supposed to mean low voltage. Battery was at 11.8 volts when I first started working on the system. I have the battery on a charger. Would a 11.8 volt battery charge make a difference in controller working or not? Like I said when I checked at the panel later after working on the system the panel shows 0 volts.

Bobertgoes · 10-23-2022, 11:41 AM

Tell us more about the panel. Is it a folding panel? These get damaged easily and do not last long anyway.
You can electrically damage the panel, yes, but if you get 18 volts then the panel is probably good. Does the panel not never show 18 volts, or still intermittent?

Controllers will go bad much more often than the panel.

Do you know the disconnect process? Disconnect the panel first, then disconnect the battery. The battery will act as a buffer to the panels high and possibly spikey current, so the battery actually can protect the controller from the panel. This does not happen often but can happen if you disconnect the battery then the panel from the controller.

Is possible for a panel to have 18 volts still yet not have the amps to charge. This could be bad wiring (or corroded or shorted somewhere), or just bad panel or bad controller.

Try connecting the panel directly to your battery and see if it gets some charge after an hour.
Not good practice, but yes, I had a bad charger that put out 18 volts and I used it for years never knowing this. Batteries would be getting charge for months on end and they lasted as many years as is normal. The lights were brighter on the 18 volts, but nothing of my DC stuff was damaged. That said, still, dont connect panel to battery as everyday practice, but just for last resort test for an hour is fine.

SJ-Chris · 10-27-2022, 06:44 PM

If you are measuring correctly with your voltmeter at the panel output wiring and there is not 18v(+/- a little...assuming your panel is supposed to be outputting 18v), and there is sunlight, then obviously there is a problem with your panel. If it is intermittent, then I would suggest you just replace the panel.

If you are getting 18v.... Does your voltmeter also allow you to switch to check amps? If so, check to see how many amps are coming from the panel. In sunlight, it should be between 2-5amps depending on tilt, time of year, etc.

If you are getting 18v, AND you are getting 2-5 amps in sunlight from your panel, then your panel is working. If not, then your panel is no longer good and needs to be replaced.

If you are getting 18v, AND you are getting 2-5 amps in sunlight from your panel, then connect all the wiring and measure the wires JUST BEFORE entering your charge controller. If you get the same healthy results (with perhaps just a little drop) then the wiring from your panel to the charge controller is good. If not, there is a problem with that wiring.

I recommend a resettable fuse/breaker between your panel and controller and also your controller and your battery. This way you can better manage things.

You should always connect your charge controller to your batteries first, and then your controller to your solar panels.

Your battery being at 11.9v should not be an issue. If your panel and wiring to the controller is good, then if you first connect your controller to your batteries, and then the controller to the panels. If things at that point don't work, it is likely your charge controller....UNLESS your batteries are somehow bad. You might want to bring your batteries to your local auto part store and have them tested.

Good luck!
Chris

Bobby F · 10-27-2022, 10:11 PM

If your panel has a small wiring access box on the back, open that up (out of the sun) and look at the rather simple wiring inside for obvious looseness or disconnects. In the sun, test voltage at various points inside the box. I've had two 100-watt panels - both Rich brand - that died, and I found the wiring had fatigued loose on one leg in both.

Pappion · 10-28-2022, 10:49 AM

I keep having problems with the MC4 connectors. Bought a cheap set of BougeRV on Amazon. Beware of solar connectors that do not claim MC4. Had a few intermittent problems.

1. Male pins don't stay put and get pushed down the barrel. Had to epoxy them in place.

2. Crimps don't hold.

Anyway MC4 is meant to be connect and forget. Not intended for many removal/insertion cycles.

Also use a contact lubricant like DEOXIT on tin plated.

B RAD · 10-28-2022, 11:14 AM

Thanks for all the replies. I learned a bunch by reading them. After testing everything I still could not find the problem. What I ended up doing was to run a new new temporary wire outside and through my window form the solar panel directly to the controller and everything worked. Then I replaced the permanent wiring wiring. It was quite a job routing the wire but it is all done now and working correctly.

SJ-Chris · 10-29-2022, 12:42 PM

Glad to hear you were able to fix it. Hopefully that was the problem.

It is a bit strange that the wiring from your solar panel to your charge controller would "go bad". Wires themselves don't often just go bad and your system doesn't have many amps flowing through it. Question: How are your wires routed? Are you dropping them through your refrigerator roof vent down behind your refrigerator by any chance? If so, do you have the wires in conduit (there are some really hot things behind your refrigerator).

Just curious.

Happy camping!
Chris

B RAD · 10-30-2022, 08:25 AM

Quote:

Originally Posted by SJ-Chris

Glad to hear you were able to fix it. Hopefully that was the problem.

It is a bit strange that the wiring from your solar panel to your charge controller would "go bad". Wires themselves don't often just go bad and your system doesn't have many amps flowing through it. Question: How are your wires routed? Are you dropping them through your refrigerator roof vent down behind your refrigerator by any chance? If so, do you have the wires in conduit (there are some really hot things behind your refrigerator).

Just curious.

Happy camping!
Chris

I know, it doesn’t make any sense to me either. My wire are routed from the solar panel on the roof and down through the wall between the main cabin and the bath. Nowhere do the wires come in contact with any heat.