I have an issue with an RV that I am hoping someone may assist. I want the relay in the BMV712 to isolate the batteries at XX% SOC and have done this for the BP 220 but most of the load in the RV is fed of the same wires as a Victron solar MPPT. I use the BMV networking to supply the MPPT with the battery Voltage and Temperature.
The cut-down circuit below is some of the existing RV electrics and there is an issues I am trying to overcome.
The makers or the RV saved some dollars by only running one pair of cables from the batteries to the cupboard over the sink and there is no way to get more cables inside the walls - well without removing the cladding.
In the cupboard is a Victron MPPT and the battery supply terminals are paralleled across to a Voltech Battery Protector so I cannot use the Victron BP 200 to protect the battery - I would get reverse current through the BP 220 when the MPPT is charging. All of the fuses that supply most of the RV electrics are after the Voltech unit.
My Question is, looking at the picture below, I can get a pair of wires from the batteries, under the floor and over to the door switch that controls the Voltech, Unfortunately the Voltech uses negative wire switching and the BP 220 uses Positive switching.
I use the normally closed contact to open at 25% capacity.
If I connect the BP220 terminals 2.1 and 2.2, BMV and connect the Voltech control wire as shown in the picture below, I believe I could achieve this what I want but it really depends on the manual being right for connection 2.2 as the BMV would connect both terminals to battery negative.
In normal operation the BMV N/C contacts provide a circuit to the Voltech via the RV isolator switch inside the door and the BP 220 is enabled with 12V on terminal 2.1.
When the BMV goes below 25% capacity, the relay changes state and removes the battery negative so the Voltech cannot enable and the BP 220 terminals are now at battery negative so it should disable the BP220.
I would think the BP 220 should be able to operate indefinitely with its terminal 2.2 shorted to battery negative - is this correct.