Feature Request: DESS Tarrif dependent PV production

Q&A and troubleshooting DESS
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1

My PV system (3 x Growatt) is controlled with Node-RED via Tasmota and Modbus.

When the sell tariff is below zero, Node-RED keeps the maximum grid feed in of the PV between - 100 and - 300 watt to prevent losing money during this period and keeping the Victron at maximum charge power. (When I would regulate around 0 watt, I disturb the charging process, which lowers the charging current).

When the buy price is below zero, the PV production stops because buying energy is cheaper than generating, the Victron should optimally charge at full power during this block to earn money and keep the grid more stable.

Logically, this causes the PV forecast to become inaccurate.

Can a configurable option be added that Victron is aware of this regulation (tariff dependent PV generation option) and uses the negative tariffs in solar forecast?

Here is an example of the forecast being inaccurate, probably due to PV regulation in the past:

Screenshot_20250430_075355_VRM
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Here is an example of PV production regulated at a grid feed in of 100-300 watt (complete PV stop was not implemented yet):

Screenshot_20250430_075804_VRM
Screenshot_20250430_075804_VRM1080×1908 158 KB

2

Unfortunately, DESS doesn’t charge during negative tariff when PV is switched off. It should charge the most during negative tariffs because it generates more money and keeps the grid more stable.

Screenshot_20250501_185921_VRM
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Note: There was a small tariff difference between Node-RED and Victron, causing PV to be switched off for 2 hours instead of 1 hour.

3

@mpvader Can you put this feature request on a wishlist?

Negative prices are becoming more common, stopping pv production now causes wrong prediction.

Screenshot_20250511_110421_VRM
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4

Price is extremely negative (-23ct/kWh), pv is shutdown because of this, but dess is discharging instead of charging at maximum power to earn money…

Screenshot_20250511_122329_VRM
Screenshot_20250511_122329_VRM1078×8506 283 KB

5

I’m suspecting it’s not charging (and earning) from the grid because you’re already at Target SoC ?

6

When I set the target SOC to 100% it started charging immediately, so the battery is not full yet.

7

Hi Jeroen, I had the same problem when switching off my AC-coupled PV inverters using Home Assistant… but only the first day.

The day after, it looked like DESS understood wat was happing and also predicted the AC-inverters would be switched of during negative prices.

Don’t change the settings and have patience for a day and see what happens.
I’m curious if it works for you also.

8

Thank you! I will keep monitoring it.