Victron MPPT 150/45 not charging - Array shows half voltage when hooked to CC. Full Voltage when disconnected

[Core2]

24v LiFePo4 battery bank.
600Watt of solar panels
Victron 150/45 CC

It was a nice sunny day today and on my way out the door to my vehicle I decided to check on my system to see how much power it was bringing in. The app said 0W. Shocked, I checked the battery status 39%. It should be pulling in ~400W at that time of day. I didn't have time to troubleshoot then, so I switched off my array. This evening when I finally had time to troubleshoot the system i discovered the voltage from the array was about half of what it should be. I have six 12v panels wired in two 3-panel strings, then wired in parallel. Typical array voltage is ~60v at peak solar. This evening with a sitting sun, the array, unplugged from CC, was 52.2 volts. When hooked to the CC it was 25.xx volts. I unplugged each string of 3, and tested the voltage 52.2V and 52.8V. I placed one string at a time in the combiner and tested after the inline fuse. Each string read the same voltage previously stated. I left only one string connected and tested at the CC. It was half the voltage. So I swapped out the 1st string with the second string. Same issue, half the voltage. I then broke out some extra wire i had laying around and bypassed the inline fuse, and breaker switch and went straight to the CC. Same issue. Half the voltage. What gives? Is my CC shot? Is there something wrong with the panels?

Any suggestions for testing would be appreciated. I have an old junker CC that was given to me. I will see if it can charge my type and voltage of battery with it. It could be a good test to isolate the problem down to the Victron CC.

 

[#40Fan]

Try a reboot. Remove both battery and PV wires for a few minutes.

He finally gets around to it later in the video, so maybe this will help. His was the 150/35 though.

 

[Core2]

I will go unhook it now. Tomorrow morning I'll hook it back up. Thanks.

 

[yodamota]

the voltage without the Array being hooked up and when its hooked up will always be different. I believe when its not connected you are seeing the VOC.

In my opinion one of the panels is shot. Being that the charge controller is a 150v unit. why not hook them all up in series?

Any chance we could get a screen shot of what you are seeing when the voltage is at 25.xxx ?

 

[Core2]

@#40Fan It's doing the same thing, showing ~half the array voltage.

@yodamota I will try that now. Trying each string separately, and see the same problem, would indicate the same issue in each string. What's the chances of each string having a panel go bad?

 

[Tomthumb62]

I will go unhook it now. Tomorrow morning I'll hook it back up. Thanks.

Unhook the panels FIRST, then the batteries. Many charge controllers aren’t happy if they’re connected to PV but not battery. Not sure about Victron.

 

[Core2]

@yodamota, This was an interesting test! hooking the two strings up in one big series string results in a VOC 118.4 volts. When i connect them to the CC, it shows the about the SAME voltage as yesterday, 26.13V! This is peculiar. I expected it to half the array voltage. I believe this indicates a problem with the CC. I will start a service ticket with Victron.

 

[Core2]

Good news I got it running again.

I have a junker Renogy PWM CC. I used the same bypass wires I used in yesterday's test, except this time I terminated them with MC4 connectors. Good solid connections, no doubt they are connected. I wired up the PWM CC with the first string of panels and got 5A into the bank. I then hooked up the second string and got 5A into the bank. I hooked both strings in parallel through a Fused MC4 connector and it didn't work! I checked the fuse and it is blown! doh! So, how did yesterdays bypass test fail? I likely had crappy connections since I didn't terminate the bypass wires I was testing with.

Since the PWM worked with both strings of panels without the fuse, it was time to hook up the Victron back into the system. The moment I connected the solar array up to the Victron CC it started dumping current into the bank!!! The fuse was to protect the wiring and not the CC. I'll replace the fuse soon. It was 15A a little to close to maximum amps from the arrays.

Sorry for the false alarm. Lesson learned don't cut any corners when troubleshooting.

 

[Core2]

It's bugging me how this played out. If the in-line arrary fuse was blown, then why would the CC react when I connected and disconnected the array? How did it sense it was connected if the circuit wasn't complete?

 

[Tomthumb62]

It's bugging me how this played out. If the in-line arrary fuse was blown, then why would the CC react when I connected and disconnected the array? How did it sense it was connected if the circuit wasn't complete?

Your guess is as good as mine. Sometimes we don’t get to know. Can’t tell you how many times I took something apart, put it back together and it worked.

Recently I rewired my camp trailer. Add I was replacing the SCC to battery negative cable from 10awg to 8awg, I discovered that the SCC screw terminal was loose!! No wonder our AGM batteries were getting such a poor charge!

 

[mikefitz]

The fuse was to protect the wiring

With a two string array, fuses are not needed and can never offer any protection to the panels or cables.