Morningstar controllers include many electronic protections including load protections. This includes overcurrent, short circuit and high voltage disconnect (HVD) protections. The overcurrent and short circuit protection provide more reliability and robustness to the load circuitry, particularly when the controller is used with large or highly capacitive loads.

Overcurrent Protection is implemented in software and is intended to protect the controller from exceeding the load current rating. Morningstar controllers continuously measure the load current and cause a software-triggered shutdown of the load terminals if it exceeds the nameplate current rating. An example of this would be a user sequentially turning on small loads until the total load current exceeded the controller’s rating.

Short Circuit Protection is implemented in hardware and is intended to protect against rapid increases in load current. Rapid increases in current can be caused by a sudden short circuit of the load terminals or from a startup surge when switching on a load with high capacitance. This hardware protection circuit is tuned to allow the highest amount of current possible (for as long as possible) without damage to the MOSFETs. Only when the current (or duration thereof) approaches a harmful level does the hardware protection activate to shut down the load terminals. Extensive destructive testing was conducted in order to determine the optimal tuning point for the protection circuit.

A more detailed description of these protections is available for the SunSaver™ Gen 3 Controller in the Load Overcurrent & Short Circuit Protection in the SunSaver™ Gen 3 Controller tech doc.  https://www.morningstarcorp.com/wp-content/uploads/technical-doc-load-overcurrent-short-circuit-protection-sunsaver-gen3-en.pdf

The protections for other Morningstar load control equipment have the same type of overcurrent and short circuit protections.

These protections may not protect the controller from damage under all circumstances and our product warranties will not cover systems that have been damaged by over-current. Also, the built-in overcurrent protection is not a substitute for external overcurrent protection for the load circuit. 

Startup surges can have inrush currents that are at least 3 times higher than the continuous current of the load. Pumps and DC-DC converters are examples of the type of loads that may have startup surges. When designing a system, one should determine the max startup surge for the device being powered. Some capacitive loads include a slow start feature which limits the startup surge. Inverters have extremely high DC input surges. Therefore, Morningstar’s DC load control should never be used with inverters.

Many inverters, like our SureSine inverter, and DC-DC converters include LVD load control and should be wired directly from the battery as shown in our Inverter wiring diagram. https://www.morningstarcorp.com/wp-content/uploads/tech-note-diagram-inverter-wiring-en.pdf 

The SureSine inverter and many inverters and DC-DC converters include remote on/off control terminals that can be used for implementing LVD. For example, below is a diagram for SureSine Remote LVD using a Relay Driver.

It is also possible to use external relays which can handle higher load currents and surges. It is important to select the proper relay or it can be damaged. Most electronic supply dealers provide a search tool that includes a filter in order to help identify relays that will meet the voltage and current requirements for your loads. 

The Relay Driver is designed to be used with relays. However, it is also possible to use a load controller to turn on and off external relays that the load controller can’t handle. We have a tech note which shows how to do this. https://www.morningstarcorp.com/wp-content/uploads/tech-note-diagram-tristar-load-control-with-inverter-en.pdf

HVD protection is provided for systems that have loads that may get damaged with higher voltages. Many 12V loads are rated to 15V and 24V loads are rated to 30V. Unlike Solar HVD, Load HVD is not temperature compensated. To avoid the loss of load during charging, the maximum regulation voltage of the controller needs to be lower than the Load HVD setting. The charge settings are temperature compensated so if there is a possibility that the charge voltage will get too high in cold conditions it is possible to set the max regulation voltage charge setting lower than the HVD voltage. This will limit how high the charge voltage can be.