I have a lithium battery providing power to my 12v refrigerator. If there is a problem with the lithium battery and the BMS shuts the power off, I want to be able to switch to an alternate power source so I don’t lose all my food. I found a cheap (poor quality) automatic DC switch on amazon. I dont trust the quality.
Can I use a Victron MPPT 110/20 with its load output to function as an automatic switch? In its original design, the load output derives power either from solar (1st - 12v source) OR battery (2nd 12v source).
Why not use an automotive bosch style relay? Connect the lithium battery positive to the NO contact and the switch contact, and connect the alternate dc source to the NC contact. When the lithium battery is on, the relay is energized thus supplying power to the fridge from the lithium battery; when the lithium battery shuts down, then the relay is de-energized and the fridge is supplied by the alternate source.
I have two independent systems. using single, isolated lithium battery as primary power. I have not connected the ground wires to the two separate systems
You could still accomplish this using 2 relays. One for the positive and one for the negative. The upside would be that the relays are readily available if a failure were to need replacement.
It isn’t clear how you want the Victron MPPT load output to work. It’s always connected to the battery and will disconnect the load output when the battery voltage drops below the specified voltage. It can be use to turn on/off a relay, sort of like the Smart BatteryProtect.
Note that the output amps are rated the same as the charge amps.
This is briefly covered in Tech Talk #9.
