Local-only Marstek Venus e-battery integration with Home Assistant | Hacker News Reader

Local-only Marstek Venus e-battery integration with Home Assistant

du.nkel.dev

16 pointsHelmut1000110 comments

Nice write up! The new version Marstek Venus E 3.0 now natively supports modbus TCP via the normal network connection if you upgrade the firmware. So with that one you can skip the Waveshare setup.

Not sure if that would fit for the requirement of the author to have no "Chinese IoT devices" on the LAN.

800 W is que conservative for a schucko plug, which is typically rated for 13 or 16 A (>3000 W). I regularly charge the car at 10 amps (2400 W) on a schucko.

Yes! However, we are not allowed in Germany to use more than >800W on a Battery with a Schuko Plug, without a certified electrician. Everything is regulated! :D

I have been waiting for the electrician to hardwire the battery for about six months. He said he would stop by next week. Once he has done that, I will increase the maximum charge/discharge power to 1500 W (conservative, I know, but I think I don't need more to fully charge/discharge the battery on regular days).

I don't think this is a Schuko limitation... 800W is a limit that you can send back to the grid without having a properly registered PV plant with a normal inverter. Your meter might disconnect you if you try to send more.

Yes, sorry. I think it is a battery policy regulation in Germany that prevents >800W.

He has 30 kW solar so the registration with the grid operator already happened.

This isn't a grid limitation but a rule about safe home installations. The limits are low for things the general public gets to plug in on their own. Those simple limits don't apply to the same battery installed by a professional. Professionals would instead follow a more complex set of rules and make some calculations, allowing for much higher currents if done in the right way.

What you say is correct. Except: As the AC battery was installed four years after the PV system, I did have to register it separately with the grid operator, which included creating a new entry in the Martstammdatenregister. In other words, registering the PV system and the battery were two completely separate processes for me.

The problem is not the plug itself but the rating for the circuit it's connected to. If there is a 16A breaker for the circuit to protect the wiring from overload but you add 10A via a plugged in battery you're now allowing a total of 26A to flow through those same wires.

The 800W is a compromise, the wiring for a 16A circuit (typically 2.5 mm2) is able to handle 20A without a fire risk.

If you install the same battery in a fixed setup by an electrician it would be on a dedicated circuit so the only limit is the wiring of that circuit and the breaker you let them install. They would then also consider limits on the upstream wiring and things like earth fault protection.

I had separate circuits installed for my solar and future battery, using 4 mm2 wiring and 25A breakers. Only a small change to the central installation swapping the earth fault protection for one that was rated for higher currents.

Super interesting! With such a big solar system, the self-consumption is already quite high. With a smaller solar system, the ROI for a battery would probably be higher. So in itself a big solar system is a nice alternative to batteries. Curious about the details of the 30kWP solar setup!

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