Standalone local-first energy controller for DIY solar and battery storage

Been mulling this over for a while, ever since I got the static caravan setup running properly last summer. The Victron ecosystem is brilliant, don't get me wrong, but there's always this nagging feeling that you're beholden to their cloud, their app updates, their servers being up somewhere in the Netherlands.

What I actually want is something that runs entirely local — no subscriptions, no phoning home, no "service unavailable" message when I'm trying to check my Fogstar battery state at midnight in a field.

Specifically thinking about a controller that:

• Handles charge prioritisation (solar → battery → load shedding) based on local rules you set yourself
• Works with common BMS protocols (JK, Daly, etc.)
• Has a dead-simple web UI that runs off the device itself, not a cloud portal
• Fails safe — if the controller dies, everything defaults to a sensible state

The Raspberry Pi route is obvious but I've had enough SD card failures on the motorhome to put me off. Something like a dedicated ARM board with proper flash storage feels more right.

I know Venus OS gets close to this, and honestly it's decent — but it's still Victron-centric and the configuration rabbit holes are deep.

Has anyone actually built something genuinely agnostic? Happy to hear about Home Assistant approaches too, though last time I tried that the automations felt fragile for anything safety-critical.

Interested whether people think this is a solved problem I've just not found, or whether there's actually a gap worth filling here.

TransitProject | 847 posts

@DaleSpirit Know exactly what you mean - that nagging feeling is essentially "what happens when the cloud goes away or Victron decides to deprecate something?"

I've been running a Raspberry Pi with Node-RED as the brains of my van setup for about 18 months now. Completely local, no external dependencies. It reads from the Victron kit via the VE.Direct USB cables and makes all the routing decisions itself.

The beauty is you define your own logic - time-of-day priorities, SOC thresholds, whatever you need. Mine even factors in a basic weather API cache so if connectivity drops it falls back to the last forecast gracefully.

Not exactly plug-and-play, but for anyone comfortable with a bit of tinkering it's surprisingly robust. Happy to share my Node-RED flow if that'd be useful to anyone.

Been there with my narrowboat — the day my GX device had a wobble mid-winter was the day I started taking "local-first" very seriously indeed.

For a genuinely standalone controller worth exploring:

• Node-RED running on a Raspberry Pi with Victron's local MQTT — no cloud dependency whatsoever
• Venus OS Large unlocks this natively on a Cerbo GX
• ESPHome for lightweight edge logic if you're handy with a soldering iron

The beauty is your Fogstar batteries, Renogy panels — everything still talks locally even if the internet goes down completely. Rule-based automation sitting on-site means your SOC thresholds and load priorities are always enforced regardless of what Victron's servers are doing.

@DaleSpirit the static caravan use-case is actually ideal for this — simpler loads, predictable patterns, perfect for tuning local automation rules without losing your sanity.

@DaleSpirit @RetiredChef This resonates strongly with my motorhome build. What I ended up doing was running a Raspberry Pi alongside the Cerbo GX, pulling data locally via the Victron VE.Direct interface and making load-shedding decisions entirely on-device — no cloud dependency whatsoever. Even if the Cerbo goes offline, the Pi continues cycling my Fogstar 280Ah cells safely based on local SOC thresholds.

The key architectural principle worth considering: treat the "smart" controller as an observer and override layer, not the primary protection mechanism. Your BMS still handles hard limits; the local controller handles intelligence.

One gotcha — make sure whatever you build fails safe. Mine defaults to "charge only, no heavy loads" if the control logic crashes, which has saved me twice already.

Worth looking at Node-RED for the logic layer if you want something maintainable without heavy coding.

PeakVanLifer | 312 posts

@SimonKelly raspberry pi route is fine until the pi decides it's not. been there.

what I actually run in the shepherds hut is a dead simple ESP32 setup talking to the Victron gear over VE.Direct — no cloud, no subscription, no drama. if the router dies nothing changes, batteries still charge, loads still switch. that's the point innit.

garden office is similar, Fogstar cells with a basic BMS and the ESP32 just watches SOC and controls a couple of relays. nothing fancy but it works offline by default, cloud is just a bonus if it happens to be up.

the problem with most commercial controllers is they're designed cloud-first and local is bolted on after. should be the other way round.