House Battery Charging the Yeti fix
I donít know if others have found this, but Iíve found in late afternoons when the solar isnít putting out much power, the Yeti car charger will pull power from the house batteries and, if left unchecked, will deplete them a bit. Obviously, this isnít desirable, and I have to remember to unplug the car charger so they donít drain too much. My car charger cuts off at about 12.5V which is a bit low for our needs.
To keep the Yeti from draining from the house battery, I used our BMV712ís internal relay to automatically control the Yeti car charger. When the solar is charging the house batteries the relay closes and charges the Yeti. Once the voltage starts to drop on the house batteries, it opens the relay and stops charging the Yeti. The BMV712 relay is rated at 1 or 2 amps; certainly not enough to power the 5 or 10A Yeti car charger. So I used the BMV712 relay as a switch to power a low current draw 25A solid state relay to control power to the Yeti car charger outlet. The relay and fuse, and fuse holder were less than $25.
the BMV712 relay is programmable. Iíve found that turning on the BMV712 relay when the house battery is at or above 13.2 volts works well. I shut it off at 13.1 volts. A few days of dry camping over the 4th of July weekend showed that the relay control worked as planned. On a late afternoon in a tree shaded spot on a partly cloudy day, I watched the relay open and close with the solar output. One morning our house batteries were at 70% and the Yeti was at 80%. By late afternoon, the house batteries were at 100% and the Yeti was at 83% after running two laptops all day and charging various devices. The solar output was 780 WH for the day.
Iíve found the Yeti is a great addition and it adds to the comfort and convenience of our Airstream. This easy, inexpensive upgrade makes it even better.