MAKITA 12V MODULAR UPS POWER SUPPLY

I have designed this modular cover for makita 12v battery so I could use like a little UPS for my router and fiber optics module to have always internet connexion. My house is off-grid with solar panels and li-ion battery. If something happend to any of the inverters and they cut power if there is any problem I would be able to connect them only if I have power on my internet system if I am not at home. Also I add a hole to mount 12v car usb power supply or also you can instal a 12v car cigaret socket. For turn on and off you could use regular 20mm 12v switch. The idea is to connect the 2 12v power sockets for the router and the fiber line on the inlet, those will always maintain the battery charged. The battery would have connected 12v regulator to stabilize the 12v even if the voltage of the battery drops while using it. My router and fiber line control box use both of them 5,5X2,1mm regular power sockets. Also I will add a BMS to protect the battery. You could also use this to power up other things and custom the internal or electronics. BMS: 3S BMS as show in the photos. DC-DC: LM2596S DC-DC 4,5-40 V.