OpenEVSE - solar charging or battery limit charging

Been running OpenEVSE on the boat for about 18 months now and it's genuinely impressive how flexible the firmware is, but I'll be honest — getting the solar-following mode dialled in took longer than it should have.

The battery limit charging approach is simpler to set up and more predictable day-to-day. You just tell it to back off once your bank hits a certain voltage (I use 54.2V as my trigger on a 48V LiFePO4 system). Works reliably with Victron MQTT integration if you've got a Cerbo GX.

Solar-following is more elegant in theory — it watches excess PV and adjusts charge rate dynamically. In practice on a narrowboat you've got shadows, trees, bridges, cloud — the current fluctuates constantly and the EVSE ends up hunting around rather than settling. Annoying on a 3-phase install, probably less so on single phase with a smaller array.

What I've ended up with is a hybrid: battery limit as the hard ceiling, solar MQTT data as a soft guide. Fogstar cells have been rock solid throughout — no complaints there.

Curious whether anyone's using the OpenEVSE HTTP API to push custom limits from Node-RED or Home Assistant rather than relying on the built-in solar mode. I've been tempted to roll my own logic but haven't committed to it yet.

Also — has anyone had issues with the OpenEVSE dropping MQTT connection after a router restart? Mine loses it and won't reconnect without a manual reboot of the unit. Firmware 7.1.3, for reference.

@AngliaOffGrid the solar following mode is a rabbit hole isn't it 😅

Took me ages on my cabin setup to get the MQTT integration stable enough that OpenEVSE wasn't constantly dropping in and out of charge sessions. The key for me was tightening up the polling interval and setting a sensible minimum current threshold — otherwise on partly cloudy days it just becomes a mess of start/stop cycling which is worse than useless.

Are you pulling your solar data via Victron VRM or directly from a meter? I found going straight from a Cerbo GX via local MQTT was way more responsive than anything cloud-dependent.

Battery limit charging is simpler to configure but you lose all the dynamic throttling benefit. Horses for courses depending on your use case really.

Really interested in this thread - been eyeing up OpenEVSE for my setup for a while. @AngliaOffGrid did you find the current ramp rate settings made much difference to how smoothly it tracks solar input? I had a play with a friend's unit and it seemed quite aggressive by default when clouds roll in and out.

Also worth mentioning for anyone reading - if you're running it alongside a Victron system, the Venus OS integration via MQTT is fairly solid these days. Makes the solar following behaviour a lot more predictable when it's pulling proper real-time data from the Cerbo rather than relying on a separate CT clamp reading.

@EmmaEdwards82 curious what broker you ended up using - Mosquitto on a Pi I'd assume?

@AngliaOffGrid interesting you mention the solar-following mode — on my boat I ended up going a completely different route initially and just set hard limits via the API rather than doing proper solar tracking. Worked adequately for emergency backup scenarios where I just needed something rather than optimal behaviour.

The bit that caught me out was the current ramping — OpenEVSE's default ramp rate was far too aggressive for my setup and was causing the Victron MPPT to do odd things. Worth checking currentlevelchange in the config if you haven't already.

@Chunk66 the current control is genuinely granular once you get into it, but I'd say factor in a solid weekend of MQTT head-scratching before you're confident it's behaving correctly. The documentation isn't always... current, if you'll excuse the pun.

@AngliaOffGrid ran into exactly this with my static caravan setup — OpenEVSE's battery limit charging mode was the bit that actually clicked for me once I stopped faffing with solar-following entirely.

Set a SOC ceiling in Victron, let Node-RED whisper to the EVSE via MQTT when the Fogstar batteries hit the threshold, job done — car charges on surplus without me losing sleep over overnight grid bleed.

The solar-following rabbit hole is real but honestly for most UK setups where irradiance is about as reliable as a British Bank Holiday, battery limit charging is the more robust approach — you're essentially smoothing out all that cloud-chasing nonsense automatically.

@Chunk66 if you've already got a GX device it's genuinely plug-and-play once you've wrestled the MQTT topics into submission.