Something wrong with the MPPT 75/15 / load output

DIY
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Hello Victron Community
I ve run into a few problems after i changed my 12 v battery to a 24v lifepo one.

So far i had the Battery connected to the battery in of the MPPT. My Loads were connected to the load out of the mppt. I havent changed the way i connected it not, at least until now but more of that later

  1. The load output data was displayed correctly at 12V; I always had a load of about 30 watts. This hasn’t changed since switching to 24V. However, it no longer displays the load correctly.Most of the time, it shows 0W, even though I’m running the above-mentioned setup. Every now and then, it jumps to a plausible value (approx. 30W), then back to 0W, stays there for a while, and sporadically jumps back to 30W, and so on.
    The odd thing is, when it shows 30W and I then turn on a 250W fan heater, the value jumps to 0W.
    2 days ago, it started at about 30-50W in via solar, and it also shows that the battery was charging at this moment about 1.2-1.8A, but that can’t be happening if I’m drawing more than 10A on the load output.

The more solar power came in, the more power the load output displayed, sometimes exceeding 120 watts even though I was only drawing 30 watts. And when I ran a 250-watt fan heater for testing, as described, the power at the load output dropped to 0 watts. If i disconnected it it jumped back to 95-120 watts.

Of course, I switched the battery voltage from 12V to 24V before switching. I also set the correct battery type (Lifepo).
What did I do wrong? Or is the problem with the MPPT?
I already had answers in the German section of this forum but unfortunately these answers were anything but helpful

2.They said the load output wouldn’t work at 24V, so today I disconnected the load output and connected my loads directly to the battery. This, however, leads to further problems:
After doing that, I turned on my devices (about 30 watts) again. Now, as you can see in the screenshot, the battery is shown as fully charged, although before that, I had a completely different battery voltage.
It is also strange that with the faulty performance at the load output, the battery never rose above 26.6 volts the 2 days before, consumption was at 12v at about 450-500 watt hours the weeks before.

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Since I have absolutely no knowledge of 24V systems, I don’t know if a load of 30 watts is too low to sufficiently stress the battery and the MPPT to detect a battery discharge. I thought the MPPT automatically adjusts the power I draw from the battery via solar energy as the battery voltage drops.

So I reactivated the load output and connected a load of approximately 35 watts, which it initially displayed correctly. Then the solar input also displayed power again.Shortly after, the power jumped back to over 100 watts, which can’t be correct (screenshot 2)

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When I turned the load off again, the battery voltage briefly rose to 33 volts. screenshot 3

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Did I make a mistake, or is the MPPT defective? That would be very frustrating, as I specifically opted for a 24-volt system for my energy storage system so I could continue using the 75/15.I can’t change anymore because I already ordered the Victron easy solar 24/3000 for 900€

I hope I’ve shared enough information to provide an assessment of the problem. I really hope you can help me, and thank you in advance.

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It looks like you do not have a good connection to your battery which is why it is showing 0.00A but enough voltage to charge. Check all your connections are good, fuses and breakers OK. If it is a new lithium battery with Bluetooth make sure that the battery is turned on and charging and discharging are enabled. Nothing wrong with the mppt from screenshots. Use a multimeter to check voltages.

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Came here to say check the lithium is ‘allowing’ charge. I know Fogstar have their own app etc.

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Ok i found the problem thanks to you. It is very Embarrassing… Ok you are allowed to laugh at me…

So i checked the voltage, Battery voltage had 25.6 volts…
Checked the voltage at the Battery in on the MPPT… 0.004 Volts…

Looks like I swapped the connections for the battery and load output… The battery was connected to the load output… Embarrassing… In my apologies, I was on the phone with my girlfriend when I connected it. lol

Then I wonder why Victron didn’t include an error indicator. 50 cents more for parts and you’d get a notification in the app. Or it wouldn’t turn on at all. Then Victron could have solved the problem without me wasting your time due to my stupidity. I apologize very much.

So why does it show it like that? It actually seems to have worked somehow. I wouldn’t have thought it was possible to connect it like that. I made a mistake because of my own stupidity, but I’ve learned from it.

It’s not easy either. I can find 6 and 10 mm² cables at the local hardware store, but they’re always only one color. That’s why the battery cables and the load-out cables were the same color. And of course, they’re laid right next to each other. Thank you all.

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Thanks for confirming, I new something was not connected right but I would never have worked out the exact problem over the internet.