The Victron system does a great job of scheduling charge times/rates to match the forecast profile. However it is reliant upon the accuracy of the forecast. In my case this is often wildly inaccurate. For example tomorrow it is forecasting that our consumption will be 2.2 kWh and the day after 1.8 kWh. As we never go below 11.5 kWh these forecasts will result in our battery being undercharged by a large margin. We have a standing load of around 250 W so having periods of zero demand is clearly an error.
An option to have User Defined Consumption profiles in DESS would be very useful. I would imagine a lot of people are in a similar situation to myself where their day to day profile is roughly the same varying only with car charging and weekends. So having the option to create and select profiles as listed below would resolve a lot of issues:
Normal
Week-end
Car Charging
Victron AI
On those rare occasions when Octopus give free, or very low cost, power the option to switch back to ESS is still there.
I would welcome other peoples thoughts on such an option.
You are absolutely right that the forecast accuracy needs to be improved. I think more factors need to be taken into account. However, I cannot confirm your statement about the low charge of the home storage. In my case, 2 wall boxes and a heat pump are controlled separately when PV production is high or when prices are low, without the DESS knowing. This usually means that the forecast is too high for standby consumption. In my particular case, however, I am not upset about this because the storage is large enough and I have some consumption reserve.
The principles of DESS are very impressive but there are things it can do well and there are things that it will never be able to get on top of:
The magic of Dess is in extracting pricing data from a supplier and working out the best times to charge the ESS. This takes away a lot of work which would otherwise be needed in scheduling charge periods.
I am a retired person and am fortunate to travel quite often. DESS will never be able to work out a pattern of use for me. However I do have discrete usage patterns and if I were able to input my consumption profiles for say a week in advance then DESS would be fantastic.
Typically:
When home I use around 13.5 kWh per day +/- 10%.
When away I use around 6 kWh per day.
When my supplier has very low cost energy I might use 35 kWh per day.
DESS cannot know if I am going away next week so it will make a guess, but it will be wrong.
Also the Average Use profile gets skewed by the sudden swings.
So if Victron can let me have a few User configured Consumption Profiles I could tell it in advance what will be happening and DESS could then work its magic on the charge profiles making adaptations during the day as it normally does.
DESS is the right idea and a very promising technology.
Current “version 1.0” is already doing a good job, and I am confident, Victron will improve it step by step.
I fully agree with @teejay that the best algorithm cannot predict what I do on purpose in an unusual way. This is input a DESS system would need on top and as manual input on user side.
Here are some thoughts in addition to Tonys proposal.
Optional DESS input on user side
Planned absence with low consumption (start/end)
Unusual high consumption (start/end)
EV needs to get fully charged for a long trip
Interface can be either VRM, or a simple UI on the GX. Nothing over-engineered, very simple. It should be as easy to use and to deploy as possible. Only complete days, no specific hours.
Regarding abnormal consumption, it might be an idea to allow tagging of days via VRM in the past or in the future for the algorithm to exclude in its forecast.
Regarding DESS and CyberSecurity
Deploy DESS following a “least privilege” principle. A VRM full control or two-way-communication should not be needed for DESS purpose only. A DESS only communication from the cloud to the Cerbo might be a good idea. Allow only steering of the parameters DESS requires.
A simple plausibility check on Cerbo side for every change from the DESS cloud can add additional robustness against potential hacker scenario in case the Victron DESS cloud gets compromised and an attacker would potentially be able to control many systems in a harmful way.
I am watching my system now as it allows direct Grid power to AC Load at a price of 21p per kWh. Having charged the batteries at around 18p per kWh the system knows that it does not make economic sense to use stored power at a Grid price of 21p per kWh as the real cost of the stored power is 18p/80% (cycle efficiency) = 22.5p per kWh. This is the real value that the fantastic Victron system delivers.
If the DESS would deliver those decisions in an optional verbose mode - maybe only on click somewhere - it would make it a lot easier for us to understand, why the current behavior in some situations and under the given circumstances is correct and makes sense
If you observe the DESS and understand the logic a little. You also know that a certain level of efficiency and battery costs are taken into account, then most decisions make sense. It is also helpful to read the detailed documentation.
