What does everyone do to automate inverter shutdown/startup based on battery voltage?

Running a Victron MultiPlus on the boat and just use the built-in low voltage disconnect — set it to cut out at 47.5V (12V bank so roughly 11.9V equivalent scaled up... wait, I'm on 48V 😅) and it's been rock solid honestly.

For the startup side I've got a Cerbo GX doing the heavy lifting. Set up a simple automation in VRM so the inverter won't come back on until the bank recovers to 52V or so — stops it from cycling on and off when the sun's barely tickling the panels.

Before I had the Cerbo I was using a cheap relay module triggered by a Victron Battery Sense, which worked surprisingly well for the price. Bit janky but got the job done over one winter.

Few things I'd suggest regardless of setup:

• Always add a time delay before restart, not just voltage — avoids false triggers from brief regen spikes
• Log your cutoff events if you can, tells you a lot about your usage patterns
• Don't rely solely on inverter-level protection, a proper BMS should be your last line of defence (Fogstar Drift cells have decent built-in protection on that front)

Curious what others are doing — especially anyone running a more DIY route without the Victron ecosystem. Seen a few posts about using ESPHome or similar for this and wondering if anyone's actually running that day-to-day on a liveaboard situation where reliability actually matters.

Graham1995 | 847 posts | ⚡ Solar Obsessive

@BenJohnson95 Ha, the 48V mental arithmetic gets everyone at some point!

On my system I use Node-RED running on a Raspberry Pi talking to the Cerbo GX via MQTT. Lets me set much more nuanced logic than the built-in LVD — so for instance I'll start shedding non-essential loads progressively as voltage drops rather than everything cutting at once. Bit more setup effort but means the fridge keeps going long after the telly's gone off, which feels more civilised.

The built-in Victron LVD is perfectly solid though for simpler setups, just remember to account for load-induced voltage sag when setting your cutoff point — what reads as 47.5V under heavy draw might actually be a reasonably healthy battery still.

BoxerWanderer | 234 posts | 🚢 Narrowboat Nomad

@BenJohnson95 Been down this rabbit hole myself on the boat. I ended up wiring a Victron BMV-712 into the MultiPlus assistant — so the state of charge triggers shutdown rather than raw voltage. Voltage alone is a bit like judging whether the kettle's full by how warm it feels; technically related, but you'll regret trusting it.

Set mine to disconnect at 20% SoC and reconnect at 50%. Took an embarrassing number of dead evenings watching telly go dark before I bothered sorting it properly. The BMV talks directly to the MultiPlus via the VE.Direct cable — no faff, no relay bodging, just a few minutes in VEConfigure setting up the assistants.

Much more reliable than voltage thresholds, especially if you've got Fogstar cells that sit suspiciously flat across most of their discharge curve.

HannahDavies85 | 412 posts | ☀️ Van & Boat Hoarder

On my narrowboat I've got a Victron Cerbo GX running a Node-RED automation that watches battery SOC rather than raw voltage — because voltage-based cutoffs lie to you like a dodgy used car salesman the moment you've got any load on the cells.

Set mine to:

• < 20% SOC → inverter off via the Cerbo's relay
• > 40% SOC → inverter back on automatically

Took about an afternoon to set up and now I barely think about it. The Fogstar Drift LiFePO4 cells I'm running report SOC properly over Bluetooth so the whole thing actually makes sense rather than guessing from a wobbly voltage curve.

BoatLouise | 156 posts | ⛵ Solar Boat Convert

@HannahDavies85 ooh Node-RED on the Cerbo, I keep meaning to go down that route but it feels like a rabbit hole I won't climb out of 😅

On my boat I'm using a Victron BMS with the load output wired to a relay that controls the inverter's remote on/off pin — keeps it dead simple. Set the disconnect/reconnect thresholds in the BMS config and honestly it just... works. No automation faff required.

Though I'll admit the Multiplus assistant stuff @BenJohnson95 could probably handle most of this natively? The "Generator start/stop" assistant can be repurposed a bit creatively for inverter control logic if I recall right. Might be worth poking around VictronConnect before adding extra layers of complexity.