Hi, I have a 10kva Multiplus-II with excess solar. This is in a Shed, completely Off-grid. I also have a 7Kva Generator connected to this 10kva Multiplus. I also have 5kva Easy Solar in a house approx 50meters from the shed, no Generator. Can I connect Output 2 of the 10kva to the input of the 5kva and enable the output based on SOC to supplement the 5kva. Also considering using Node Red and MQTT to have the 5kva requesting the 10kva to start the generator and enable AC2 when the house is low on SOC.
In case no one more competent than me answers.
I’m pretty sure youtuber Andy, off-grid garage has/had this setup. Around 2022/23 if memmory serves me right. Lots going on in his channel so it can be a bit challenging to locate the right video. I think this one is a starting point: https://www.youtube.com/watch?v=H5nO7-AQA68
Edit: In the video description Andy has a link to a video explaining the setup.
Yes possible but not officially supported
Yes absolutly possible. We have done this with 3 Multiplus. We build our own grid. We have a master and to slaves, all ESS enabled. We store power from master to slaves and from slaves to the master.
@RainerW are you offgrid? Curious to know how you are using ESS in an offgrid setup.
No, the master is ongrid and all other work as slave on the AC Out of the master. But this works also if the master is off grid. You can see a offgrid ESS as a system with ongrid power failure.
For anyone interested, I have completed this install and as described, everthing controlled via a Raspberry Pi MQTT server running Node red. Works exactly as I have thought it would, still need to do some fine tuning on the 3 Multi-plusses as they can overwhelm my 7kVa generator. Below is the “logic” for anyone keen to have a bit of a read.
Architecture Comment
DISTRIBUTED SOLAR GENERATOR CONTROL SYSTEM v1.0
Three installations monitored via MQTT bridges to central Pi.
Install A (CCGX 606405f1a85e) - 5kVA MultiPlus, BMV-700, MPPT 150/100
-
On Starlink subnet 192.168.1.10
-
Provides: SOC, Low Battery Alarm
-
No generator, receives AC from B via AC Out 2
Install B (Cerbo c0619ab7c7c5) - 10kVA MultiPlus, 2x MPPTs
-
On LAN 192.168.0.58
-
Has generator on AC In, AC Out 2 feeds A and C
-
Relay 1 = generator, Relay 2 = AC Out 2 (via AUX input)
Install C (CCGX 4006a0fb5b65) - 5kVA MultiPlus, MPPT
-
On LAN 192.168.0.153
-
Provides: SOC
-
Receives AC from B via AC Out 2
Node-RED is the SINGLE BRAIN - all decision logic runs here.
Cerbo auto-start DISABLED. VEConfigure assistants removed except AUX->AC Out 2.
Decision Engine Comment
DECISION ENGINE LOGIC
GENERATOR START (any ONE condition triggers):
-
A SOC < 60%
-
A Low Battery Alarm (level 1 or 2) → forces 1hr minimum run
-
B SOC < 50%
-
C SOC < 50%
GENERATOR STOP (ALL must be true):
-
A SOC >= 95%
-
B SOC >= 95%
-
C SOC >= 95%
-
If alarm-triggered: 1hr elapsed AND alarm cleared
AC OUT 2 CONTROL:
-
Generator running → AC Out 2 ON automatically (via AC In)
-
B SOC >= 95% → Relay 2 ON → AUX closed → AC Out 2 enabled
-
B SOC < 80% (gen not running) → Relay 2 OFF → AC Out 2 disabled
DATA FRESHNESS:
-
All inputs must be < 2 minutes old
-
No action taken on stale data
Output 1: Generator START/STOP commands
Output 2: AC Out 2 ON/OFF commands (via Relay 2)
Command Router Comment
COMMAND ROUTER & SEQUENCER
START sequence:
1. Send generator ManualStart = 1
2. Wait 60 seconds
3. Send AC Out 2 ON (legacy - now handled by Decision Engine Output 2)
STOP sequence:
1. Send AC Out 2 OFF
2. Send generator ManualStart = 0
MQTT Write Topics:
Generator: W/c0619ab7c7c5/generator/0/ManualStart
Relay 2: W/c0619ab7c7c5/system/0/Relay/1/State
Monitoring Comment
MONITORING & SAFETY
- Gen State Feedback: Confirms generator actually started/stopped
Topic: N/c0619ab7c7c5/generator/0/State
Values: 0=Stopped, 1=Running, 2=Warm-up, 10=Error
- Data Watchdog: Alerts if no data for 5 minutes
- Home Assistant notifications:
-
Immediate alert if Node-RED goes offline
-
Daily health check at 7:00 AM
- All services (Mosquitto, Node-RED) auto-start on boot