Charge Battery when Price is low

[Urbautz]

Currently I am planning to charge my battery when the tibber price is "low".
I will switch to Tibber in April, but i have already made some plans how to control when to charge.

Anyone got a better idea or an already existing automation feel free to share.

Running every hour at minute 2:
IF before 10AM
   AND it is not sunny
   AND forecast below 7kwh for today
   AND price below 75% of daily average
-> Charge
IF between 10AM and 3PM
   AND it is not sunny
   AND forecast today below 4kwh for today
   AND battery state below 50%
   AND price below 75% of daily average
-> Charge
IF after 3PM
   AND it is not sunny
   AND forecast today below 4kwh for today
   AND battery state below 50%
   AND price below 75% of daily average
-> Charge
   AND forecast tomorrow 4kwh for today
   AND battery state below 50%
   AND price below 75% of daily average
-> Charge

Running every hour at minute 58:
-> stop charging

[marq24]

I am with Tibber now since mid of October and since then I am running a very simple automation...

IF price < daily_average and price@(now + 6h) >= daily_average
-> Charge
else
-> STOP

So six hours before the price is above daily_average I will charge my battery with (cheap) (external) power

Yes this totally ignores how many PV power is expected (in the next hours) - but IF there is PV power the battery will be charged with that - even if the current price is low... [have in mind when you enable the switch with the SENEC.Home integration you change the battery Independent from the source - can be PV power - or if not enough available power will be imported from the grid.

I also started with way more complex conditions & rules - I might face a special situation - I am also running a heatpump - if it's running it will take 2000W... This means the 10 kW battery (well currently just 7kW) will anyhow do not last over the night...

Once we will reach the time again, where a fully changed battery will bring me though the night I think I will keep this so simple... Once I do not have to import power from the grid during the night, the battery will be fully changed during the day... Then I am switching my HA to "Summer-mode" (which includes plenty of other adjustments like "pool control" that is not used during the winter)...

[Urbautz]

Don't you loose lots of money this way?
Cheapest gross price i have seen on tibber is 12 €cents (Germany, Frankfurt region). So if you don't consider the production of the day, you buy for 12+, and then sell for 8.10 €cents your overproduction of the day.

[marq24]

I fully agree - that's why I said, that is is my "simple-winter-mode"... I did not run into the situation yet, that I just have charged by battery with imported power and then 1/2h later I would export 1000W from the PV...

If this is the case (just like it is NOW) - I have another automation, that will increase the warm-water-temperature (as some-sort-of-secondary 'battery)' in such rare winter-situations...

But again you are totally right - WHEN there will be more PV available, that I can currently use, then this is very approach is "stupid" (buy for +2x,x cent and sell for 7.6 cents...

Currently (in Winter-Season) this is really very seldom situation - and also you might be surprised, that "high tibber prices" can occur almost during the complete 24h's (it#s not always just from 6-9 and from 16-21)...

[mager33]

Remember that chargin/discharging and storing all have losses; I'd calculate 20% total loss. So if you charge on anything other than price level "VERY_CHEAP", you'll have to make some assumption on when (i.e. at which price) you will consume how much of the stored energy

The initial proposal to charge only if price is <75% daily average makes sense to me, but looking at this month chart of relative price level (I've set up a sensor in HA to calculate that) I'd go for 70%.

Another factor is the charging power (I can charge at 3kW, that means I can charge +20%SOC per hour) - and your daily demands.
Thanks for the ideas; I'l try them this winter.

[Steph-74]

Actually, I am also charging in the winter months my battery from the grid when the Tibber price is cheap. However, I failed last winter to automate forecasted demand vs. pv production and at the same time factoring in the price spread and the charging/discharging losses. Therefore, I finally decided to have helpers in HA for date/time (start of the charging hour) and target SoC. These values need to be set manually - rest is done by automations/scripts. Target Soc actually is my choice to factor in pv production and engery consumption following the grid charging.

Espacially the charging/discharging mentioned by losses @mager33 made it more complicated: Considering those it might be better to consume for a couple of hours directly from the grid before charging the battery from the grid in the cheapest hour. And this again has two aspects (*):

• At night it is better to set the inverter into standby mode, as the whole systems is also sucking 50+ Watts
• During daytime, only the discharging shall be deactivated, as I want to charge as much from the roof into the battery to last through the night.
  For that I implemented a price limit helper. When the Tibber price drops below the price limit, either discharging is de-activated or I put the inverter into standby. Had to fumble around with Modbus, but it works out now with my Fronius inverter and BYD Battery ...

My decision tree for the night:

• Will the SoC bring us through the night? If no, the price limit will be set.
• Can the stored engery in the battery be stretched to last through the night? If no, set recharging window and target SoC

(*) and then there is a third one, as we are only looking on the "production side" so far: What consumption can be moved to this time window, i.e. dish washer, washing maschine ... and this winter I need to consider another major demander for cheap energy: BEV. As I just realised, therefore another integration from @marq24 is rather handy for me ;)

[marq24]

If you are already evcc user, then have you tried the home battery loading feature from evcc yet (when I understood this correctly, then you can configure your home battery more or less in the same way then a loadpoint...)

I can't test all that right now, since I was so foolish to become a customer of Senec - they have decided to shut down my battery completely (IMHO for no reason -not only just 70% of the capacity - it's completely OFFLINE - so right now I can't contribute anything here in this subject...

But once battery is back to normal operation I have to find a good way to control vehicle charging (in winter) and battery loading and cooking water in the heatpump.

[marq24]

UND vielen DANK für Deine gerade reingeschneite Unterstützung @Steph-74!

[Steph-74]

Yes, I did. It only supports a price limit (yet). When the price drops below the price limit, evcc sets via Modbus the OutWRte to -100, which means the battery is charged with 10KW. Additionally, no target SoC can be specified (yet).

(yet), because the feature is still experimental.

I prefere to adjust the charging power of my battery to reach my target SoC at the end of the charging window for a more soft charging. Had to think hard about calculating this last year ... and need some re-thinking now, as I changed al the helper IDs earlier this year :(.