Is it normal to have battery voltage at SCC connectors to panels?

[Jesshaines]

Ok, here's my latest obstacle/troubleshooting challenge...

I have a power Mr 60 amp charge controller, with 48 volt 16 cell battery.

I've had two panels connected for the last week or so with no issues. Well let me correct that - but more on that later.

Power Mister has two terminals for panel connection. Today I tried to wire a third panel into the second terminal pair I hadn't been using so far.

I put a breaker on the circuit and when I switched it on, a short time later I noticed a big dip in battery voltage. Checked the BMS and it appears the panel was pulling around 8 amps.

I know this can potentially be caused by failed diodes. So I switched to another panel, but the same problem.

I've checked and rechecked wiring polarity. I'll do some testing on the panels tomorrow, but I'm beginning to doubt that is the issue and for now I can't let my brain rest!

So one idea I had was to check at the mc4 connector coming out of the charge controller for voltage there. I found battery voltage which surprised me. So I checked the lines to the panels that have been working fine for 2 weeks, also battery voltage.

Is that normal?

2nd issue - on my "turn on day" 2 weeks ago, when I initially closed the circuit to the panels, nothing happened. The charge controller showed no input voltage or watts.

I won't make excuses for myself.... I became convinced that I'd reverse polarity and switch the lines around. When I close the breaker that time it immediately tripped the breaker.

I went back to how I originally had it (after pulling those two panels which definitely have blown diodes and are probably fried. Sigh. Well if the worst that happens to me on the solar adventure is too fried panels I'll count myself lucky and grateful).

This next time, everything seemed to work fine and this is the setup that's been charging my battery for the last 2 weeks. BUT - at night power Mr always reads battery voltage on the screen when there's no input.

Well if anyone read this far I'd be grateful for any advice or experience. Or just a bit of encouragement you got this keep going you'll figure it out!

I know this is a long story for a single question but I mostly wondering about battery voltage at the ends of the lines coming from the charge controller to the panels. That seems really weird. Anyone know if that is remotely normal?


Thanks

 

[time2roll]

What voltage/wattage are the panels? Are the 2 or 3 panels connected in series or parallel?

 

[Pierre]

I have two of these SCC - they seem to work but they spew RFI all over my ham shack. But anyway : those input terminals are doubled up to increase current capacity as they are in parallel. You should not reverse polarity on your cables without confirming with a volt meter. Start over by disconnecting everything from the SCC. Now confirm polarity on cables that go to your battery and connect these to the SCC. The display should light up and show battery voltage. Work trough all your settings and confirm. Now you can connect a PV panel to a pair of input terminals after confirming polarity and observe. Come back here and report.

 

[Jesshaines]

What voltage/wattage are the panels? Are the 2 or 3 panels connected in series or parallel?

Rated 285w - but they're used and so far I haven't seen more than 300 watts total from two panels in series.

Two panels are in series. A third panel I set up separately but connected to the second pair of panel terminals on my charge controller. Does that make sense? LOL I feel like it's very simple and the physical realm but hard to put into words.

So 2 in series, one single panel.

The single panel might seem weird. I can explain why I did that if necessary

 

[Jesshaines]

I have two of these SCC - they seem to work but they spew RFI all over my ham shack.

Sorry - whats RFI? Lol. I've heard they can have some weird reading sometimes these charge controllers.

Yes I know I shouldn't reverse polarity. I've checked and double checked and triple checked since I made that mistake. But what's done can't be undone.

I guess I'm trying to figure out if I may have damaged my controller with that incident or if it's more likely something with the panels.

I've been using only one of the ports for the last 2 weeks but it seems to be working more or less fine. It's just when I connected the single panel to the second set of panel connections on the charge controller that just happened

 

[Jesshaines]

Sorry - whats RFI? Lol. I've heard they can have some weird reading sometimes these charge controllers.

Yes I know I shouldn't reverse polarity. I've checked and double checked and triple checked since I made that mistake. But what's done can't be undone.

I guess I'm trying to figure out if I may have damaged my controller with that incident or if it's more likely something with the panels.

I've been using only one of the ports for the last 2 weeks but it seems to be working more or less fine. It's just when I connected the single panel to the second set of panel connections on the charge controller that just happened

Powmr display at night. During the day when the panels kick on the voltage will change and the wattage rise obviously. After dark it shows battery voltage here which seems weird

 

[Pierre]

Sorry - whats RFI? Lol. I've heard they can have some weird reading sometimes these charge controllers.

Yes I know I shouldn't reverse polarity. I've checked and double checked and triple checked since I made that mistake. But what's done can't be undone.

I guess I'm trying to figure out if I may have damaged my controller with that incident or if it's more likely something with the panels.

I've been using only one of the ports for the last 2 weeks but it seems to be working more or less fine. It's just when I connected the single panel to the second set of panel connections on the charge controller that just happened

RFI : Radio Frequency Interference.
Has the 2nd panel you connected the same specs as what is connected to the first input ? Voc and Vpower point should match. Unmatched panels can be connected in series as long as the current , Iop is similar.

 

[Mattb4]

Rated 285w - but they're used and so far I haven't seen more than 300 watts total from two panels in series.

Two panels are in series. A third panel I set up separately but connected to the second pair of panel terminals on my charge controller. Does that make sense? LOL I feel like it's very simple and the physical realm but hard to put into words.

So 2 in series, one single panel.

The single panel might seem weird. I can explain why I did that if necessary

Your second set of PV terminals on the SCC are not for extra panels. Especially not for matching in parallel one panel with two in series. That is like trying to parallel a 12 volt battery with a 24 volt battery. The extra terminals are to allow two sets of smaller wire that can carry the amperage of your solar array without needing large more expensive wire.

Yes you will read voltage on those terminals once the SCC has charged up its capacitors from your panels.

 

[Jesshaines]

Yes you will read voltage on those terminals once the SCC has charged up its capacitors from your panels

Thank you! Umph, feel quite foolish...

 

[Jesshaines]

The extra terminals are to allow two sets of smaller wire that can carry the amperage of your solar array without needing large more expensive wire

Ok ?

Looking through Will's book and SCC manual, I don't see this diagramed....only single lines to SCC.

 

[Goboatingnow]

Ok, here's my latest obstacle/troubleshooting challenge...

I have a power Mr 60 amp charge controller, with 48 volt 16 cell battery.

I've had two panels connected for the last week or so with no issues. Well let me correct that - but more on that later.

Power Mister has two terminals for panel connection. Today I tried to wire a third panel into the second terminal pair I hadn't been using so far.

I put a breaker on the circuit and when I switched it on, a short time later I noticed a big dip in battery voltage. Checked the BMS and it appears the panel was pulling around 8 amps.

I know this can potentially be caused by failed diodes. So I switched to another panel, but the same problem.

I've checked and rechecked wiring polarity. I'll do some testing on the panels tomorrow, but I'm beginning to doubt that is the issue and for now I can't let my brain rest!

So one idea I had was to check at the mc4 connector coming out of the charge controller for voltage there. I found battery voltage which surprised me. So I checked the lines to the panels that have been working fine for 2 weeks, also battery voltage.

Is that normal?

2nd issue - on my "turn on day" 2 weeks ago, when I initially closed the circuit to the panels, nothing happened. The charge controller showed no input voltage or watts.

I won't make excuses for myself.... I became convinced that I'd reverse polarity and switch the lines around. When I close the breaker that time it immediately tripped the breaker.

I went back to how I originally had it (after pulling those two panels which definitely have blown diodes and are probably fried. Sigh. Well if the worst that happens to me on the solar adventure is too fried panels I'll count myself lucky and grateful).

This next time, everything seemed to work fine and this is the setup that's been charging my battery for the last 2 weeks. BUT - at night power Mr always reads battery voltage on the screen when there's no input.

Well if anyone read this far I'd be grateful for any advice or experience. Or just a bit of encouragement you got this keep going you'll figure it out!

I know this is a long story for a single question but I mostly wondering about battery voltage at the ends of the lines coming from the charge controller to the panels. That seems really weird. Anyone know if that is remotely normal?


Thanks

If your charge controller is pwm as opposed to mppt , then the battery terminal voltage will be seen ( as an average ) at the PV output. You need an oscilloscope to see the pwm action.

 

[12VoltInstalls]

The extra terminals are to allow two sets of smaller wire that can carry the amperage of your solar array without needing large more expensive wire

So basically they are parallel connections- so OP can use a second 2S pair of panels- 4 total, 2S2P- and that should be fine is how I’d read that

After dark it shows battery voltage here which seems weird

That is probably what it’s designed to do

Rated 285w - but they're used and so far I haven't seen more than 300 watts total from two panels in series.

in bright sun at 80*F that might be right. See what one panel will do. I get 250W+ when it’s hot from one 400W array frequently. In very cold conditions I could see nearly 400W with vertical panels because they’re not hot.
Panel Watt ratings are generally given at 77* with a temperature coefficient (say “.25” or “.3”) that means for tc=3 you lose .3% for every degree over 77 and gain .3% for every degree below 77*F. Many panels are similar in coefficient. All are not similar in temperature coefficient. Then there’s resistance of the connections, connector, and wire, and typical ~15% inefficient- that also reduces actual output. So at 285W you could ‘lose’ roughly 45 watts just by putting a load on the panels. The load in your case is the SCC.

Does that make sense?

 

[Jesshaines]

Yes - makes sense. TU!