@dognose
@dfaber
I am aware that Victron is currently taking a break from developing the DESS to see how it works. I think that’s right and good. Nevertheless, I want to try to put an idea into words. There are always particularly cheap days, especially in connection with dynamic pricing. I have been observing/using the DESS for almost 15-16 months now. I am aware that “buying” at particularly cheap times and then using it unconditionally does not always make sense according to the current functions of the DESS. Hence the idea of a special function…? With this “special purchase” you could then enter a price below which the storage device charges the storage device up to a specified %Soc. As a practical example, “below €0.16 charges the battery up to 85% Soc”. It would be important for the system to remember the price and the amount of electricity purchased and stored. The system then uses this stored energy at all times that are higher than the purchase price + battery costs + effective losses. If the kWh consumed corresponds to the kWh previously purchased at “special prices”, the system returns to normal operation. I am fully aware that such a special function requires a certain amount of programming effort. I also don’t know whether it can be implemented 1:1. But based on my observations and the many criticisms expressed here in the forum, I think such a function is very useful.
I understand the idea, but I think it doesn’t really fit into the “big picture” of how DESS is supposed to work.
The amount of energy purchased is basically a “dynamic thing”, tiny difference in consumption and/or solar later the day, may change it by some 0.X kWh scheduled to buy.
Using a hard-setted pattern like you describe would be kinda “strange” behaviour:
- 0.1 cent above your treshold-price, DESS may plan to charge 2 kWh.
- Then, 0.1 cent lower it is supposed to charge 25 kWh from grid.
I think, this is a “too special” behaviour to have it implemented as a common feature. But it should be possible to quite easily achieve this with a Node-Red-Flow. Something like: “Disable DESS → Set GridSetPoint to -X000; reset GridSetPoint and enable DESS 1-2 hours later”.
Tiny hack: When I spot days with very cheap prices, where I want to charge more than the schedule would do, I simply set the battery balancing down to 2 days, and let VRM do the roadmap to charge to 100% that day at “best prices” and “max solar usage” 
I am aware that this would be a kind of special function and would be completely different from the general functionality. Maybe someone will find a way. Apart from myself, I find many questions and comments that point in exactly this direction. I myself have a relatively large battery capacity available and use the Min Soc at these particularly favorable times. I increase it at favorable times and reduce it the following days. I don’t want to bother with programming myself using Node-red anymore. I’d rather leave that to younger people. Let’s put it this way: It’s not necessarily my “core competence”