Troubleshooting solar setup... or troubleshooting my troubleshooting!!

[thomm225]

Originally Posted by Paul Elliott

If you do make the direct-to-battery connection test, don't worry about discharging the battery to any particular level. Just measure battery voltage and panel current. If the battery is somewhere between 10 and 16V (let's hope it is) the panel current will be only slightly less than Isc if everything is right. You won't damage the battery by overcharging if your test only lasts a few minutes.

This advice is incorrect.

As the battery charges closer to fully charged the current flow will decrease ……….which will cause you to freak out thinking your panel is bad

[Paul Elliott]

Originally Posted by thomm225

This advice is incorrect.

As the battery charges closer to fully charged the current flow will decrease ……….which will cause you to freak out thinking your panel is bad

My advice is correct. With the panel connected directly to the battery (no controller), the panel current will not change a lot until the battery voltage exceeds 17V or so. Yes, this would overcharge the battery if left connected long enough, but a few minutes will do no harm.

Look at the solar panel V/I curves if you don't believe me.

[Paul Elliott]

Originally Posted by basssears

Battery voltage was 12.1 or lower, sometimes 11.9 or so, as I had the high beams and driving lights on to make sure I had a load... the battery definitely wanted more power than the panel/controller was giving it, so I don't think it's that.

Either the controller is bad, or you have an intermittent connection. A solar panel won't oscillate.

Originally Posted by basssears

I still plan on trying this (nothing to lose as I voided my warranty with my mounting setup), only problem with the straight voltage test is even if the panel brings the battery up in voltage I still don't know how much the panel is really putting out... I mean, a 5 watt panel would eventually bring my battery up, just like a 50 watt panel putting out 5 watts. And I unfortunately don't (currently) have a "known good" panel to use as a baseline time wise.

But we shall see.

You are getting various opinions on how to test, most of them pretty good. But you have the tools at hand (voltmeter, ammeter) to get this figured out simply and quickly. You don't need to watch the battery voltage slowly climb if you can measure the current your panel is delivering. How fast the battery charges is a function of battery size and charging current. If the panel is delivering close to the rated current, then the problem is not in your panel.

Do yourself a favor and look at the I-V curve for your panel. Here's the spec for a Renogy 50W monocrystalline panel: https://www.renogy.com/template/file...ifications.pdf. The last page, bottom-right shows the curve. You will see that the current is virtually constant between 0V (short-circuit) and 15V (a well-charged battery, probably overcharged.) The current drops from 2.84A at 0V to 2.7A at 18.5V. The spec has a typo, saying "Short Circuit Voltage" where it should read "Short Circuit Current" -- don't be confused by that.

From what you've shown us, it looks like you have three good panels and one bad panel. Perhaps the good panels are marginal, but you need better testing to tell for sure. Until then, I suggest that you verify your panel tests (no controller, no battery, just open and short circuit tests), and then try your good panels with a different controller to see if that helps.

[noelex 77]

Paul is correct. When testing the solar panel without the controller it is the current that will best indicate if the panel is performing correctly.

In good sunny conditions the panel should put out close to its Imp of 2.70 amps, especially if you angle the panel towards the sun. It should deliver close to this current over a wide voltage range. So the voltage is not as important to measure as the current, if you only have one multimeter. Keep the test short.

[thomm225]

Originally Posted by Paul Elliott

Either the controller is bad, or you have an intermittent connection. A solar panel won't oscillate.



You are getting various opinions on how to test, most of them pretty good. But you have the tools at hand (voltmeter, ammeter) to get this figured out simply and quickly. You don't need to watch the battery voltage slowly climb if you can measure the current your panel is delivering.

He did all the current testing and still wasn't totally sure about the results which is why I suggested the slow but sure test of one panel to battery charge. He's been at this for about a month so simply and quickly are not in the equation at this point which is again why I thought it best to simplify things or basically start over as if a new tech were starting on the problem

Also, I'm still seeing information showing the charge current will decrease as the battery nears full charge

But as I mentioned earlier, I've never had a panel fail (but I didn't drill into mine) only controllers and batteries.

1. Bulk Charge

The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no “correct” voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.
2. Absorption Charge

The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging.

[thomm225]

Originally Posted by noelex 77

Paul is correct. When testing the solar panel without the controller it is the current that will best indicate if the panel is performing correctly.

In good sunny conditions the panel should put out close to its Imp of 2.70 amps, especially if you angle the panel towards the sun. It should deliver close to this current over a wide voltage range. So the voltage is not as important to measure as the current, if you only have one multimeter. Keep the test short.

Current will tell you but the voltage and panel charge time as compared to a good panel will also.

The problem will probably come down to the drilling, a loose connection, or the controller but I'd doubt you'd throw a panel away because the wattage didn't reach max which is another reason I suggested the simple test to see if it would charge the battery alone no controller. (monitor current if you must but you don't need to)

It would also be nice to know though when the panels last worked. Did they work correctly after being drilled into. If so connections (which I've asked OP to check or redo many times) or controller ( battery condition is a guess) ………………….panel #2 is acting strange and hopefully you are hooked up directly to it's J box with new wire on that one no splices


Btw, I did see one of those Renogy Panels yesterday (100 Watt), and it look very good and well built

[noelex 77]

Originally Posted by thomm225

2. Absorption Charge

The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging.

The proposed test is without a controller so there is no absorption phase. The absorption phase is where the controller gradually cuts back the current delivered by the panels to maintain the absorption voltage. No controller = no cut back.

So without a controller the panels will deliver whatever current they can depending on the level of sun and the battery voltage. As Paul has pointed out the panels can deliver almost the same current over a wide range of battery voltages. The current will remain almost exactly the same at just above 2.70 amps until the battery voltage climbs to about 16v. If the battery voltage rises further the current will only fall very slightly. It is 2.5a at 19v. These results are for a panel temperature of 25°c so in the real world the transition voltages will be lower. However, we can say that if the panel is working as it should do in full sun it should be delivering close to 2.70 amps. It should deliver this same current irrespective of the battery voltage unless we let the battery voltage climbs to very high levels and even then there will only be a slight reduction to the measured current.

Thus, as Paul has pointed out, we can test the current and ignore the battery voltage providing we keep the test short to avoid damaging the battery.

[Paul Elliott]

Originally Posted by thomm225

Also, I'm still seeing information showing the charge current will decrease as the battery nears full charge

1. Bulk Charge

The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no “correct” voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.
2. Absorption Charge

The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging.

True with a controller, or with a constant-voltage charging source. For all reasonable voltages the solar panel is a constant current source so the charging current will not significantly taper off. This is why we use controllers with solar panels; to avoid overcharging the batteries.

There's nothing wrong with using a voltmeter to check your solar panels, but since the OP also has an ammeter I think he can quickly cut to the chase.

Simplify the testing:
1) Test each panel for Voc and Isc. Use direct sun if you can, but if it's cloudy that's no big deal and you can still compare the four panels.

2) If the panel gives reasonable results, good. If not, toss that panel (perhaps fix it later if you can).

3) Connect a good panel to the controller, and the controller to a not-full battery. See if how quickly it charges, monitoring the charge current and battery voltage if possible. If the results are bad, check your wiring and connections. If these are good, try a different controller. The problem is not in your panel, since you've already checked it.

We may need to discuss series and parallel connections with MPPT controllers, but I haven't checked out the OP's controller details. I am assuming that the panel configuration is appropriate for the controller.

Drilling into the panel frame may void the warranty, but it won't damage the panel. Drilling through the cell substrate and plastic / glass covering may cause damage.

[thomm225]

Originally Posted by noelex 77

The proposed test is without a controller so there is no absorption phase. The absorption phase is where the controller gradually cuts back the current delivered by the panels to maintain the absorption voltage. No controller = no cut back.

Right, we (I) we're talking about charging the battery directly from the panel. No controller. The way I read it the internal resistance of the battery decreases current flow as it nears full charge. I tried the Renogy link provided above but it didn't work. I'll check again later.

Just like the test I explain way above. My test took maybe one hour but I could see it was working in 10-15 minutes and even took a current check since so many here can't seem to troubleshoot without it

Again, I'm going by the it's not working or it is scenario not is it working perfectly which is why I'm not so worried about the exact current reading.

I got .8 amps (1 Amp) during the charge from 12.4- 13.1 on my 65 watt panel at 5 pm with tiller, boom, or my head blocking the panel

Results panel good.

Yesterday when I arrived, it should have read 13.7 Float, but was at 12.6 and the little battery icon should discharged one level. Problem connection at the controller which I fixed with my fingers. Batteries charged back up in 30 minutes or so to float

[thomm225]

Originally Posted by Paul Elliott

True with a controller, or with a constant-voltage charging source. For all reasonable voltages the solar panel is a constant current source so the charging current will not significantly taper off. This is why we use controllers with solar panels; to avoid overcharging the batteries.

There's nothing wrong with using a voltmeter to check your solar panels, but since the OP also has an ammeter I think he can quickly cut to the chase.

Simplify the testing:
1) Test each panel for Voc and Isc. Use direct sun if you can, but if it's cloudy that's no big deal and you can still compare the four panels.

2) If the panel gives reasonable results, good. If not, toss that panel (perhaps fix it later if you can).

3) Connect a good panel to the controller, and the controller to a not-full battery. See if how quickly it charges, monitoring the charge current and battery voltage if possible. If the results are bad, check your wiring and connections. If these are good, try a different controller. The problem is not in your panel, since you've already checked it.

We may need to discuss series and parallel connections with MPPT controllers, but I haven't checked out the OP's controller details. I am assuming that the panel configuration is appropriate for the controller.

Drilling into the panel frame may void the warranty, but it won't damage the panel. Drilling through the cell substrate and plastic / glass covering may cause damage.

See Op's original 0 volt post as I remember where all this started.

As far as charge current, I was basing my opinion as to current on internal battery resistance as the battery charges

[Paul Elliott]

Originally Posted by Paul Elliott

We may need to discuss series and parallel connections with MPPT controllers, but I haven't checked out the OP's controller details. I am assuming that the panel configuration is appropriate for the controller.

I just checked the OP's "Victron MPPT 75/10" controller, and it should work with his panels, either in the original series-parallel arrangement, or with four panels in parallel (four in parallel is near the controller spec limit for current). The controller requires at least 36 cells in series, and the Renogy RNG-50D panels do have 36 cells. The controller is supposedly more efficient with two "12V" panels in series.

So the configuration isn't an issue.

[CatNewBee]

Originally Posted by Paul Elliott

I just checked the OP's "Victron MPPT 75/10" controller, and it should work with his panels, either in the original series-parallel arrangement, or with four panels in parallel (four in parallel is near the controller spec limit for current). The controller requires at least 36 cells in series, and the Renogy RNG-50D panels do have 36 cells. The controller is supposedly more efficient with two "12V" panels in series.

So the configuration isn't an issue.

do it parallel, less fuss with shading and current wise non matching panels.

[Paul Elliott]

Originally Posted by thomm225

As far as charge current, I was basing my opinion as to current on internal battery resistance as the battery charges

That panel will still be putting out 2A even if the battery somehow gets to 20V. Here's that link to the panel specs again (it works for me): https://www.renogy.com/template/file...ifications.pdf

To be brutally honest, I don't trust the OP's original measurements well enough to base any conclusions on them. It appeared that he was trying to test too many things at the same time. I've learned over my many years to simplify as much as possible when troubleshooting. Doing otherwise leads to chaos and confusion.

[CatNewBee]

Paul, I am happy, you manage that many years without serios accidents.

anyway, many of your advices are bordrline. It is a bad thing to overcharge batteries, espeacialy SMF, GEL, AGM... They simly die hard. Another point is your lack of knoledge regarding battery chemistry, internal resistanse and voltage / currents during a charge.

The current is driven by the voltage difference between source (in this case the panel) and destination (battery) and the internal resistances of the battery at a particular SOC, resistance of the source and the cabling. This is the only thing, that defines the measured Voltage by the way, because the battery resistance is way lower than the resistance of the panels. It is also the reason, voltage alone tells you nothingabout the health of a panel.

When the battery gets full, the voltage difference drops, the resistance of the battery grows and this reduces effectively the current. Well, a 50Wp panel will not hit that limit probably, but with larger arrays and a smaller car battery, you will not see currents near Imp when the battrry is full, regardless if you use a controller or not.

Encouraging people th connect the panels without a controller and charge batteries that way is a bad thing too, especially inexperienced newbees could cause a lot damage to their batteries this way.

[Paul Elliott]

Originally Posted by CatNewBee

Paul, I am happy, you manage that many years without serios accidents.

I appreciate your concern.

I stand by my advice here, and I have been quite clear regarding the need to avoid overcharging during direct-connection testing.

Originally Posted by CatNewBee

The current is driven by the voltage difference between source (in this case the panel) and destination (battery) and the internal resistances of the battery at a particular SOC, resistance of the source and the cabling

Just what is it that you don't understand about solar panel I-V curves? During normal charging, the panel voltage is irrelevant, as the panel is truly behaving as a constant-current source (just look at the I-V curve). And so, the "difference between source (panel) and destination (battery)", etc, are also fairly irrelevant. The panel *current* is what controls the charging current, at least until we insert a controller in the circuit.

Originally Posted by CatNewBee

This is the only thing, that defines the measured Voltage by the way, because the battery resistance is way lower than the resistance of the panels.

Can you explain what you are trying to say here? Of course the battery resistance is way lower than the panel resistance. The panel, being a constant-current source, has a nearly infinite resistance. Are you talking about the measured voltage of the *panel*? If so, yes, with no controller the panel voltage = the battery voltage (plus connection resistance * charging current).