RV with built in WFCO Converter/charger: how to let SBMS0 control the charge?

[Jeff King]

I have changed my conventional RV/Trailer from lead acid batteries to a Winston LiFePO4 2P4S battery bank with SBMS0 controlling a DSSR20 to cut solar panels going into a Victron BlueSolar (no remote) SCC.

The trailer has a built-in WFCO 55A Converter/charger for when using shore power. How do I get the SBMS0 to cut off charging when single-cell voltage gets to the set point?

The problem has a few complications:

- the converter/charger charges the battery when plugged into shore power, but is also the load for the 12V loads. There is no separate charge line and load line. 

- there is another load/charge line that connects the battery to: 

  1. emergency break-away breaking system in the event the trailer separates from the tow vehicle.

  2. the power tongue jack at the front of trailer

  3. 12V connection to the 7-pin tow vehicle. this provides charging from the tow vehicle alternator

The WFCO converter/charger puts out a 13.6V charge level, so overall, it is conservative and doesn't drive the batteries too high. However, an out of balance pack could cause a single cell to go higher than 3.55V.  I intend to replace the converter charger with a better model from Progressive Dynamics that has a setting for Lithium profile, so outputs a 14.2V charge level.  Regardless of which converter/charger, the fact that both load and charge is a single connection presents a barrier to allow the SBMS0 to cutoff charging and separately loads.

[nebulight]

It's challenging when components like this do two functions. In this case, because the output power to the 12v loads isn't coming from the battery, but instead 120v AC, I would mainly concern yourself with disconnecting the output on the charge side (since if you are connected to the charger and you have an over voltage, the converter will disconnect and it will power the DC loads through the battery). One way to accomplish this, is to put a victron 100 amp battery protect on the output of the converter. Install it 'backwards' so that the input is the converter and the output is the battery as current can only flow in one direction with these battery protects. Then wire up the SBMS extio3 to the remote ports of the BP100 so that when an over voltage condition happens, it will disconnect the converter output to the battery.

There are two versions. The smart battery protect (which has bluetooth to program and control) https://www.victronenergy.com/battery_protect/smart-battery-protect

And the normal non bluetooth https://www.victronenergy.com/battery_protect/battery-protect which I think they still make and is $20 cheaper. However on this unit, the label is load and battery. The battery side would go to the converter and the load side to the battery. Confusing, but these are designed to protect a battery from under voltage. However they work totally fine in this applicaiton and the new units changed the labels.

[Dacian Todea]

Jeff,

I will suggest using a SSR on the AC input and just have that controlled by the EXT IO4 set as type 1.

For Load you will need to install something like a Victron battery protect able to disconnect all your DC loads and that will connect to EXT IO3 set as type 2

You will need to be able to separate the loads from the charge sources else battery can not be protected.