MPPT going not loading battery, despite way higher voltage coming from solar panels

[michaelliebe]

According to the documentation I need to have minimum 5V more inbound than the battery needs.

My current setup generates ~73 volt from two solar panels. The battery (LiFePO4) needs 28V. It is 51% charged.

No matter how often I disconnect, reconnect, try different orders, the battery just won’t load.

I did not find this in the community questions yet, if there is a thread I missed, happy to join there. Thanks for any help or suggestions.

[mac]

Why does the MPPT say 28.41V and the battery 25.98V? Are these screenshots taken at the same time?

[chrigu]

Check the connections between MPPT and battery, both positive and negative, including fuses. Also verify with a multimeter that both voltages visible in the APP are correct. Im sure theres a bad connection or a blown fuse. If theres no current flowing, they should both register the same voltage while they are connected.

[michaelliebe]

No, the battery screenshot was taken a day earlier, in the Liontron App it jumps a bit. I just checked now and it says 25.98 V on the battery.

[michaelliebe]

Thanks, I checked everything multiple times, but I might replace the fuses just to be sure. So it should be the same voltage on Liontron (battery) app and victron-mppt-app when the connection is good? Are the different voltages an indicator of a broken connection?

[pwfarnell]

Yes, the different voltages are the result of a broken connection.

[pwfarnell]

If the MPPT is at the set output voltage of 28.4V and there is no current flow it is because there is nowhere for it to go.

one common cause is the use of cheap unbranded breakers like these, thay often do not work correctly.

[michaelliebe]

Thanks pwfarnell!

this is the fuse that came with the kit back in the days when I ordered the MPPT. I was just too lazy or shy to take it out. Now without any fuse, and everything works excellently! Thanks for your help!

[michaelliebe]

UPDATE:
I took out the original fuse, I guess it was too small or had already disrupted a while ago.
I guess I was afraid to change the cable setup, but now - without the fuse in the cable - everything works well. The fuse in the MPPT converter is still installed and working.

(in case you are wondering about the lower Voltage compared to yesterday: I had pimped the panels to run in series in order to increase current, to be sure its not that. Now they are back in parallel, and with the sun today, thats more than enough.)

Thanks everybody for the fast and useful help!