Fuse Fault MPPT charger 100|20

DIY
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1

Hello everyone,

the 25A Fuse of my MPPT charger blows repeatedly.
I am operating a 48 V off-grid PV system with two solar modules of type Schwaiger SOPA6450 connected in series, each rated at 450 Wp (Voc = 39.68 V, Isc = 14.15 A). The modules are connected to a Victron BlueSolar MPPT 100/20 charge controller through a 20 A DC circuit breaker, which is used only for safe disconnection of the modules.
The charge controller is designed for 12/24/48 V systems and has a maximum PV open-circuit voltage of 100 V as well as a maximum charge current of 20 A.
On the storage side, there is a 48 V LiFePO₄ battery with an internal BMS, but without any communication link between the BMS, inverter, and charge controller.
The battery can be disconnected via a main switch and is additionally protected by a 50 A fuse.
A Victron VE.Direct 48/1200 inverter is also connected to the battery and supplies the AC loads (refrigerator, lighting, USB chargers).
The problem is that the internal 25 A fuse of the MPPT charge controller blows after several hours of normal operation. I would therefore rule out a short circuit or reverse polarity.
After replacing the blade fuse, the charge controller no longer responds and none of the LEDs on the charge controller light up. After replacing the charge controller, the blade fuse blows again, and after replacing the fuse once more, the charge controller still does not respond.
Does anyone have an idea where the fault could be and perhaps even a solution?
The datasheets for the components can be found at the following links:
PV modules: https://static.toom.de/produkte/bilder/10520069/produktdatenblatt_10520069_01.pdf

MPPT charger:

https://www.victronenergy.com/upload/documents/Manual_BlueSolar_MPPT_75-10_up_to_100-20/29694-MPPT_solar_charger_manual-pdf-de.pdf?utm_source=perplexity

4

did you connect the DC loads and the inverter to the Load output?

5

Reads like the tripped fuse is not the main issue here. You are burning up MPPTs which in turn lets the fuses trip. The question should be why the MPPTs die.

Do you have any insight into that BMS? Did it switch off in the past, to protect the cells from overcharging? Since that could lead to a voltage spike on the remaining DC system, which is fed by the MPPT.

What are your charge settings?