I have a DESS system active with Trade mode that 99% works great as intended. 3 x MP2 5000, Cerbo, 60kWh of LG Chem via BMS can in DVCC. Fronius 10kW AC and 450/200 MPPT, and 2 solar fields with 19 kwp Solar(with another 8,2kWp to be addded in the spring as overpaneling - 4 x 9 panels for 450/200).
My only gripe with DESS is during low hourly buy/sell prices for the entire known 24h or so. If there is quite large volatility in hourly prices, the Trade mode works great and I am more than happy with it. But when the prices are flat for the day, say like 0,01ā¬ lowest and 0,05ā¬ highest, the DESS trade mode seems a bit too eager to cycle the battery even at a loss. I have added the transfer costs to the DESS formula(for it to have a correct purchase price vs sell price), but still it sometime, not always, wants to sell the battery to a 20% ish SOC even with 5 sent sell prices(transfer cost alone is 7,3 cents). Most of the time I have charged the batteries to 80-90% during the night(not in 4-5 summer months thou) with 7 cent transfer fees with energy fee of less than 1 cent. To be self consumed or to be Traded at a better time.
Has there been talks of Victron adding a āminumum sell priceā using the DESS formulas that the user can define? With me it is basically just āSpot energy priceā with no other multipliers as there are in the buy price(VAT tax and transfer fee). I would set this to 8-10 cent(AC-DC-AC conversion losses).
I just want to set a fixed minimum for the BATTERY discharge to grid and just forget about DESS afterwards, now I have to supervise it daily because of this irrational discharge behavior.
For direct solar to grid export, this would not apply, since I am happy to sell the excess even with 1 cent/kWh if I cannot use or store it. BUT I do not want to use battery capacity for export with such low prices. I would like to keep that as a reserve for more profitable days and a buffer for grid failures.
Does anyone know if there are roadmaps planned for such a ābottom BATTERY sellā price option?
This would make me 100% happy to leave DESS trade mode fully automatic 100% of the time, without constant monitoring if I need to disable DESS and use ESS for half a day as I do now.
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I just had an idea while posting the price calculation picture.
If I overly estimate(say 0,10ā¬ for example) the battery kWh cost. Will this effect the DESS logic at which delta it will export from battery to Grid?
This would remedy the situation completely. I will test this right now. But does someone know that exact logic of the DESS Trade mode if it will include this battery cost to the calculation for exporting decisions? Or is it just for the PnL graph where you can see the daily profitability?
Search is (supposed to be) your friend but I donāt think youāll be all to pleased. The only realistic option to get DESS Trade working great, is to get proficient with Node-RED and join the club of community DESS developers. If the last 12 months (or longer even) of discussions around this topic are any indication of what can be expected in terms of further developments and improvements on Victronās end that is. Not to bash Victron, I assume it is simply still very much a niche application for which it is hard to find the justification to invest a lot more engineering resources into. Many if not most feature request or even debugging topics are seen as edge cases Iām afraid (even if not) and quickly move from the technical to the business domain about priorities. That said, there are many people building DESS use case specific solutions themselves with good results. We do that as well and Iām trying to find ways to make that more of a centralized (community) effort but just as applies to Victron, time is scarce and other priorities often get in the way with us as well.
On the upside, it a good day to top up and balance your batteries tomorrow. Now if only Victron would port that damned āb_goal_SoC / b_goal_hourā feature from the Node-RED DESS to the VRM DESS scheduler, or make the Node-RED DESS scheduler 15 minute pricing compatible, then I could finally refactor our hybrid DESS Trade flow to be 15 minute pricing compatible as well. I dearly miss the ability to optimize such trading opportunities automatically (as was/is working great with hourly pricing).
One technical hint: donāt go down the tweaking of core settings road, I have yet to see a solution that way, keep those as close to their actual values and functions as possible. Do start monitoring the behaviour of the scheduler by building VRM advanced graphs and Node-RED flows. Once you start to figure out what is really happening āunder the hoodā, things get a lot clearer on what needs to be done to make DESS do what you need it to do.
Appreciate that tip, but I will stick to Victronās DESS algo. It is so close to being perfect FOR ME that I donāt see the point of wasting my time in study of the NodeRed platform.
Letās just keep this thread focused on this. Anyone know if that Battery cost figure does anything?
Yes it allows the scheduler to calculate when itās cheaper to run from grid energy than from cycled (stored) battery energy and visa versa. Set prices correct and decide whether you need to earn your battery back. If so ā¬0.10 / kWh is a realistic minimum, if not ā¬0.05 will see a lot more trading (=short term profit). The business case with actual write-offs is pretty marginal, lots of big boys eating that cake already. And then things change completely with solar and lenient āsalderingā regulations, for as long as that still lasts.
The scheduler is agnostic to the absolute price levels, it pretty much calculates with the deltaās only. We went another route to achieve the same goal, and I do appreciate it seems counterintuitive at first, but in practice it does make sense to instruct the scheduler not only only to target the minimum SoC st the end of the known pricing schedule (or a bit beyond even) but also to target a maximum SoC at an earlier point in time. The reason that works is that it is much more predictable what the right time of the day will be optimal to have the most energy stored, than that it is to use price limits to decide when not to discharge. In my experience anyway. There are ways to do this but they all require Node-RED Iām afraid, canāt do that with DESS as-is because the ESS scheduled SoC is not available (well it is but doesnāt do anything) when running DESS mode 4 automatic a.k.a. VRM DESS.
It is pretty trivial to do what you want with Node-RED though: read the scheduled price of the moment, set the minimum price, and override the strategy to 1: self consumption (or 2: pro battery) and the target SoC to whatever is the current SoC of the current time slot. That way you donāt have to mess with other settings while the scheduler will happily adjust to the new reality (not having sold what it planned to sell) at the beginning of every new hour. Come to think of it, you probably get away with just setting schedule 0 through 4 SoC to the current SoC (every 5 second tick) when the price is below your limit and be done with. Maybe Victron (or possibly a professional integrator) can assist you doing that, I donāt think Victron is likely to implement the same idea as a standard option in VenusOS/ VRM DESS. Not anytime in the foreseeable future anyway. If you find somebody, Iād happily share a few doās and dontās to help you āhit the ground runningā
