I have a small 75/10 MPPT in my RV with a single 200W panel. If I disconnect the PV cables from the MPPT, I read 19V. If I plug it in, I read the battery voltage. From what I can tell, that’s normal behavior when the MPPT is deciding not to charge the batteries. I am wondering though because a few days ago I had similar voltage and the unit was producing current. I think I know the answer, but I want confirmation. I think my SmartShunt (which I have configured on the same SmartNetwork) is telling the MPPT that it doesn’t need charging, so the MPPT is staying off. The other option is it could be that the MPPT knows itself how to detect when the batteries are full and stop charging.
Please post the settings of your mppt.
The smartshunt only posts voltage to the mppt, gives no instructions.
Thanks, Ludo. I wasn’t expecting the shunt to “give instructions” to the MPPT, but I was expecting the MPPT to made decisions based on the information the shunt posts. In the manual, it says it uses the shunt to determine the voltage at the battery so it can account for the voltage drop of wiring (mine is very minimal).
I took the SoC down to ~98% and I have sun shining on my solar panel. I’m expecting to see something closer to Voc for the panels right now - something around 18V based on my experience with the panel. I haven’t disconnected the PV inputs to the MPPT, but while connected, they read a lower PV Voltage (which has me confounded). It’s possible there’s just not a lot of light on the panels, but even if that’s the case, I wonder if it’s the intended behavior for the PV voltage to be less than the battery voltage when there’s not enough light, but the same as the battery voltage when there is but the battery is full.
Here is that trend screen. You can see where I unplugged the shore power and put a couple of loads on it to bring the battery down a little. It’s also interesting to me that those loads are reflected in the PV Voltage signal.
And here are my settings…
One more thing. Here’s some data from March 1-3 which is the last time I saw it collect solar. I was doing some capacity testing, but the battery voltage wasn’t exceptionally low and the days weren’t exceptionally bright. I don’t think anything has changed since then in the system.
Disable the smart network.
You have a GX.
The two are not designed to work together
Ah. Thank you so much.
I’ve disabled the Smart Networking on all devices. Thanks for that tip, @lxonline. I haven’t seen any difference in the PV Voltage even on a rather sunny day today. The PV Voltage read the 13.3V (battery voltage) all day today.
I’m still not sure if that’s the way it’s going to behave when the battery is not calling for any charge. I can draw it down some to test, but I suspect it’s not going to work.
I still need help with this if anyone knows what might be going on. I implemented a Node Red flow that stops charging from grid at a set SOC, so I’m holding the battery around 65% in case the solar is has not been collecting due to lack of need. Every day when it gets light out, the SmartSolar PV Voltage goes from 0 to about 13.5V (battery voltage) and stays at that level until it gets dark. Before a specific date, it never held at battery voltage - it corresponded to the light level (as I would expect).
Again, I’ve checked the fuse in the SmartSolar and it’s fine. What else could be holding this at battery voltage and keeping me from yielding any solar?
You need to test it independently and see what is going on there.
Test everything from the panel to the battery (including cabling and lugs)
If it works independently then it is something in the system causing the behaviour.
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Thanks, lxonline. I wasn’t sure how to test the panel alone, but I learned. I was getting intermittent readings inside the trailer. I suspected a junction I created inside a wall, but it tested fine. I went up on the roof and disassembled the junction that goes through the roof and found it to be poorly crimped. After fixing that, the Voc and Isc tested consistently and upon plugging it back in to the MPPT it’s working great. So nice to have this fixed.
Fantastic.
The downfall of many solar set ups.
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