Charging differences

Hello!
Anyone with ideas on this issue.
2 systems with same panels set the same angles about 2000ft apart. Identical panels , batteries and charge controller. Both stated at 67% in the AM. Both nearly identical loads. One charged to 100% by 3PM , the other only got to 91% by sun down???? This difference in charging has been an issue for weeks now. What could cause such differences?
Thanks.

gray webber said:

Hello!
Anyone with ideas on this issue.
2 systems with same panels set the same angles about 2000ft apart. Identical panels , batteries and charge controller. Both stated at 67% in the AM. Both nearly identical loads. One charged to 100% by 3PM , the other only got to 91% by sun down???? This difference in charging has been an issue for weeks now. What could cause such differences?
Thanks.

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What state of charge are the battery banks at before the sun comes up?
Are there shadows on one bank and not the other?
Are one set of panels dirtier than the other?

Are the batteries new?

Do you have a DC clamp meter? You can see if there is any discrepancies in current flowing before and after the charge controller as well as in the battery cables.

Could be a high resistance connection somewhere. Do you have a infrared non-contact temperature gun to look for any hot connections in the systems? Check at midday when current would be strongest. You may be able to find a hot connection by feeling with a bare hand but I wouldn't recommend it. I scorched a fingertip a few weeks ago on a hot fuse holder. Found the problem though.

Do you have any readings for output from both arrays? Several possibilities might be the cause. Like those JF mentions plus there could be loose connections, a battery going bad, a solar panel going bad or simply a misunderstanding about total load on each array causing less available power to charge the batteries fully.

John Frum said:

What state of charge are the battery banks at before the sun comes up?
Are there shadows on one bank and not the other?
Are one set of panels dirtier than the other?

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Both started at 67%
Batteries both 2022 age
One set in line for 5 months before other set.
No shadows on either bank.
The dirt issue is one item to check???
We are neighbors and friends, I think we should compare notes at same time for wattage gains. This might expose differences?
After three more sun hours of charge he was still no higher then 91%? Too much power not getting into his batteries?

littleharbor2 said:

Are the batteries new?

Do you have a DC clamp meter? You can see if there is any discrepancies in current flowing before and after the charge controller as well as in the battery cables.

Could be a high resistance connection somewhere. Do you have a infrared non-contact temperature gun to look for any hot connections in the systems? Check at midday when current would be strongest. You may be able to find a hot connection by feeling with a bare hand but I wouldn't recommend it. I scorched a fingertip a few weeks ago on a hot fuse holder. Found the problem though.

Click to expand...

Good ideas. Yes, I have those things. In a few days I can get there to do these checks.
Yes-a weak connection could blend off power fast.
Thanks, will report on finds

gray webber said:

Both started at 67%

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Shunts can get out of sync with the actual state of charge.
Also there could be more resistance between the charge controller and the battery in one system.
Look for hotspots during peak sun.

One other remote possibility is different charging parameters on each SCC. People play with things.

All good things to check on. Will do early next week when out there.
Thanks to all.

Information to add to this discussion:
The primary cables on the system are copper clad aluminum wires? They have proper ampacity but could this be the issue?
During charging and discharging the amps are no where near the rating if the wire.
Just need to be sure this is ok wire?

Aluminum wire needs to have an anti corrosion compound treatment at the terminals. Aluminum oxidizes very rapidly and can cause hi resistance connections. Noalox Special ID is the industry standard coating for battery and any other corrosion prone connections. Whether this applies to copper clad I'm not sure. So, both systems have the same copper clad wire? I'd still look at all connections for a hot spot.

Only the low charge system has CC aluminum. Just discovered after a bit of review. Not sure there is anti ox used?
I’m leaning towards connector issues or hot spots? Will test this week and report.

Both of you have CCA wires?
While copper wire’s expensive comparatively, the cost to buy new wire is not life-changing on the grand scale of things.

Also: are the solar panel cables terminated with MC4s? Many people have no issues but here in northern Vermont I chased my tail for many months from fall to spring iirc with corroded MC4s and water ingress in the wire sheathing itself. I changed MC4s multiple times until finally realizing two things:

1. Different brands of MC4s- amazingly- do not always provide a waterproof connection.
2. The water ingress was likely due to cold temperatures and snow/rain/wet. As the sun hit, things got warm, and cold meltoff would let water suck its way into the connectors from the wire sealing rubber compression ferrules.

My solution was A) replace ALL MC4s with brand new single-brand connectors. I chose BougeRV as they were inexpensive in lots of 24 pairs (or was it 30?) and had solved some of the water issues when I did both the males and females. B) After crimping with a proper B-crimp tool and insertion into the fittings, I squeezed some lexel into the fitting, pushed the rubber compression ferrule in, then covered that with lexel before tightening the compression nut down and wiping off the squeeze-out.
End of problems for over a year now.

That may not be your issue but it was mine and created extremely poor charging.

12 Volt
Another item to check out as I was not there for that part of his install. Good item to check on. ?

gray webber said:

12 Volt
Another item to check out as I was not there for that part of his install. Good item to check on. ?

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Along with proper crimps inside the connector. No flat crush-crimps allowed.

Copper clad aluminum is a red flag.
Makes me wonder what else is sub-optimal and/or dangerous.

Upon learning this I acquired pure copper wire to replace leads. No other aluminum in the install.
Function and safety first.

"Nearly identical loads" is not identical, so I don't expect identical results.

At 3 PM in the winter, the PV output is falling quickly, so you don't have much charging remaining from the PV.

Issue solved . What was wrong and done to correct it?
Checked panel gain between both set ups.
Within 7% so I did not believe it was panels.
Did an amp check out of charge controller. Checked out ok.
Decided to change out any copper clad aluminum wires. Found one and changed it.
Got an immediate jump on the battery charge monitor of 10%???? While changing out that wire we added anti ox to all main power connections and added extra crimping to primary cable ends.

Here is my thought: There was some terminal that was not good when heavy loads are carried but not bad enough to heat up for laser thermometer to find. A cable /terminal crimp may have been weak. Adding anti ox and checking torque was the final action. Removing the aluminum may have played a role in the repair?

One or all of these actions together appears to have solved the charge issue. We checked and found that now both systems added 10% charge in the same time frame.
Now both systems start at about the same 77% in the AM and charge to 100% about the same time.

Wish I could be more precise on the cause but no one item stood out and in doing the upgrade on wire connections , we only wanted to shut the system down one time .
It worked)). What ever it was?

Alu cables are the Devils own creation ^^ :D

Always copper incl. crimp plugs.