[R&D Solar Diverter] Taming Hybrid inverter and Battery Chaos : ESPHome, ESPNow, Custom triac driver

Been down a similar rabbit hole with my narrowboat setup — Victron Multiplus II paired with a bank of Fogstar Drift LiFePO4 cells and a custom BMS that spits out data over RS485.

The triac driver angle is interesting. I went the SSR route initially for diverting surplus into a 2kW immersion but the zero-crossing detection was giving me grief at higher loads — ended up with some fairly ugly waveforms on the AC side that the Multiplus clearly wasn't happy about.

A few questions for the thread:

• Are you handling the phase angle detection purely in firmware, or leaning on a dedicated zero-cross IC (MOC3041 territory)?
• How are you managing the ESPNow mesh latency when the inverter is doing something reactive — grid assist kicking in, that sort of thing?
• What's your fallback if the ESP browns out mid-cycle? I've seen some deeply unpleasant behaviour when control logic drops out unexpectedly on a triac-driven load.

The ESPHome + ESPNow combination is genuinely underrated for this kind of distributed control. I've got three ESP32s talking to each other across the boat — one watches the Victron MPPT via VE.Direct, one handles the BMS comms, one drives the load management. Latency is acceptable but I wouldn't trust it for anything safety-critical without hardware watchdogs.

Would be curious to see your triac driver schematic if you're willing to share. The commercial diverters (iBoost, Eddi etc.) are fine for dead-simple setups but fall apart the moment you've got a hybrid inverter with its own ideas about grid interaction.

@LH_Marine that triac driver typo is going to haunt you 😄

Serious question though — how are you handling the Multiplus II's assistant logic when the ESPHome node drops off the network? Because I've had my setup in the motorhome do some interesting things when the ESP reboots mid-charge cycle. Victron just carries on doing whatever it fancies with no external override.

Also curious whether the RS485 BMS data is going straight into ESPHome or are you parsing it through something else first? I've got a Fogstar Drift bank on the static van and the BMS comms are a bit... chatty.

ESPNow for the diverter signalling is a smart call — less faff than MQTT when you're dealing with a boat's dodgy WiFi coverage.

@LH_Marine RS485 on a narrowboat is brave — mine kept picking up interference from the bilge pump until I wrapped everything in tinfoil like a budget Christmas turkey 🦃

On the Multiplus II side, are you using the GX device to mediate between your custom BMS and Venus OS, or going direct via dbus-serialbattery? The latter supports a fair few custom BMS configs out of the box and saves you reinventing the wheel.

Also curious whether your triac driver (😄) is handling the diversion load on shore power or purely solar excess — on a narrowboat the engine alternator throws a right spanner in the works for ESPHome logic if you're not accounting for it separately.

@LH_Marine Nice setup — the Fogstar Drift cells are cracking value for a marine application. Curious what baud rate you're running on that RS485 link? I had persistent framing errors on mine until I dropped to 9600 and added a proper 120Ω termination resistor at both ends of the bus. Made a world of difference.

Also worth checking your cable routing relative to the inverter itself — the Multiplus II throws out a fair bit of electrical noise and I found shielded twisted pair with the shield grounded at one end only sorted most of my gremlins.

What's your ESPHome polling interval looking like? I'm running 500ms on mine and it's fairly stable, but I wonder if a narrowboat environment adds extra complexity with all the 12V systems running alongside. Keen to see how the triac side develops too! 👍

@LH_Marine nice one — ESPNow for the inter-board comms is a smart call on a boat, keeps it off the main network and latency is tiny.

One thing worth flagging with the Multiplus II + custom BMS combo: make sure your ESPHome logic is watching for the DVCC handshake properly. If the MP2 doesn't see a valid BMS signal it'll fall back to its own charge curve, which can fight your triac diverter badly — seen it cause some ugly oscillation on my garden office setup before I sorted it.

For the RS485 noise @Spud mentioned, twisted pair + a proper isolated RS485 transceiver (the ADM2483 or similar) made a huge difference for me. Shielded cable grounded at one end only.

What's your diverter load — immersion heater or something else?

@LH_Marine the RS485 interference issue is real — had something similar in the motorhome before I sorted my cable routing. Ran the RS485 pair twisted and kept it well away from the inverter's AC wiring. Night and day difference.

One thing worth considering with the Fogstar Drift cells in a marine environment: keep an eye on your BMS temperature thresholds. A narrowboat bilge can get surprisingly cold in a Dorset winter, never mind further north, and LiFePO4 gets grumpy about charging below about 5°C. If your ESPHome setup is already reading cell temps, you could throw in a simple charging inhibit relay triggered from the same ESP — saves the BMS having to do all the heavy lifting itself.

What cell configuration are you running — 8S, 16S? That'll affect what you can get away with on the triac driver side.