Wouldn’t getting rid of the breakaway battery and using the trailer battery simplify things and clean up the tongue? Unless your trailer is new those breakaway batteries typically only last a few years anyway so it might have been bad at the time of this video. Just throwing and idea out there. Thanks for the video brother!
This will maintain the battery and keep it charged while your plugged in to the tow vehicle. You can use the battery for whatever you need it for but keep in mind, it will drain down if it doesn't get charged regularly.
It will monitor and charge the Aux battery separate of the vehicle battery and will maintain the 14v needed to properly charge the trailer battery. One year later, it still functions properly and I've never taken this battery off the trailer.
