Hi there,
Currently, an off grid MultiPlus with an AC coupled inverter is not able to automatically recover from a LVD: once the MultiPlus decides it needs to LVD, the "grid" goes down and takes the PV inverter with it.
So at this stage an additional charge controller with it's own set of panels is required to allow the system to automatically recover from a LVD.
It would be great if the PV assistant on the MultiPlus (I assume this is where this functionality would likely be implemented or possibly it could be in VenusOS too if VenusOS would be able to get the required level of control of the MP) would have a feature called "Recovery" or something along those lines that can be programmed with VE.Configure.
It would work something like this.
Imagine a LVD of 47.5V. When the battery voltage reaches 47.5V, the MP will stop inverting and wait until the battery voltage reaches 51.5V. As mentioned above this will currently never happen without intervention.
At set times of the day, for example in the morning, the MP could enter a recovery mode with the following parameters:
- Recovery V: 47V
- TTR (time to recover): 3 min
- Max AC load: 3A
- Start time: 09:00
- Interval: 15 min
- Stop time: 11:00
- Max attempts: 3
In the above example, the MP would start inverting at 09:00 provided the battery V >= 47V and the AC load remains <=3A. It will wait 3 minutes (TTR). If during that time, the MP senses that the batteries are being charged (ie. AC load = 0A as PV inverter is powering the loads and it has started to charge the battery, the recovery has started successfully.
If either battery V drops below 47V (in this example) or the AC load exceeds 3A while battery V is still below LVD, the MP will stop inverting and try again after "interval" minutes for "Max attemps" number of times. It will also stop attempting to enter recovery mode after 11:00.
A really fancy version would use the time of sun rise for a particular date instead of a fixed start time.
regards,
Jan
