Posted by Peter Kennedy on 4/4/2018 to Solar
A typical use for the load output is for a well pump. The well pump will run from the battery as long as the battery is charged. After the sun goes down and the battery starts to run down the load output will turn off and the well pump will stop.
Another use is the Street Light function. You can program that to turn a light on at sunset and turn it off at dawn, or you can tell it to just stay on for a certain number of hours. As long as there is enough power in the battery the system will operate automatically. If the battery starts to run down the program will reduce the hours that the light is running to stop the battery getting damaged.
Another use for the load output is to measure the amount of current being drawn by the device you have connected. If the system is online and connected to the VRM the load current is one of the values reported and can be graphed and documented.
This bus shelter system from Sun-In-One uses a Victron Smart MPPT 75/15 charge controller supplied by PKYS to provide lighting to the bus shelter for the full hours of darkness. The program is set to turn on at dusk and off at sunrise. The Battery Life algorithm is used to preserve the battery, so in the event of low solar yields the light will turn off early.
The load output feature is found on the following Victron MPPT Charge Controllers
Here is how the programming for the bus shelter is set up:
And the load output is set to Battery Life which means its aim is to preserve the battery as much as possible, including getting it charged to full every so often to prevent sulfation.
When a system is hooked up to the VRM it is possible to see it in action. Here is the load output graph for the bus shelter for an entire week:
And here is the solar yield and state of charge of the battery for the same period:
And finally here is a video Victron made on the subject: