Growatt SPH Series Inverter - Battery BMS protocol

Been down this rabbit hole recently with my van build and thought it worth raising here as I couldn't find much specific info.

I'm running a Growatt SPH series inverter and trying to get it communicating properly with my battery BMS via CAN bus. The Growatt docs mention support for a few protocols — Pylontech, PACE, and a couple of others — but it's a bit vague on exactly which BMS firmware versions play nicely with it.

Has anyone actually got this working with a non-Pylontech battery? I'm using Fogstar cells with a Daly BMS at the moment, and I know Daly isn't the most feature-rich option for proper inverter communication. Wondering whether it's worth swapping to something like a JK BMS or even a Seplos to get reliable two-way comms sorted.

The main thing I want is proper SoC reporting back to the Growatt and dynamic charge current control — so the inverter actually respects what the BMS is asking for rather than just doing its own thing.

A few specific questions:

• Has anyone confirmed which Growatt SPH firmware version handles the CAN comms most reliably?
• Is RS485 a better bet than CAN for DIY setups?
• Any UK suppliers who've actually tested this pairing rather than just guessing?

Feels like this is one of those areas where the theory and the reality diverge quite a bit. Would be good to hear from anyone who's actually bench-tested or real-world proven a working setup rather than just gone off the spec sheets.

Hey @Thommo9, good timing on this thread! I went through exactly this with my SPH3000 last spring.

The key thing that tripped me up was the DIP switch settings on the BMS side — Growatt's SPH expects the battery to identify itself via CAN bus using a specific protocol. If you're running Pylontech it's fairly straightforward, but if you've got a DIY pack or lesser-known BMS you'll need to set it to emulate Pylontech protocol (usually called "Pylon" or "RS485" mode depending on your BMS brand).

Also worth checking your inverter firmware — there was a batch of SPH units shipped with older firmware that had CAN comms issues. Growatt's UK support were actually decent when I rang them directly.

What BMS are you running? That'll help narrow it down considerably. Some brands need a specific cable pinout too, which isn't obvious from the manuals.

Good thread this. Worth adding that the SPH series can be particularly fussy about the BMS communication baud rate — caught me out on my shepherds hut build when I was integrating a Fogstar Drift pack.

The SPH expects 9600 baud by default on the RS485 port, but some BMS units ship configured for 19200. Easy fix once you know, but a nightmare to diagnose blind.

Also worth checking which Pylontech protocol variant your BMS is emulating — there's a subtle difference between the original Pylontech RS485 implementation and what some cheaper BMS units actually output. Growatt's compatibility list on their support portal is more useful than it looks, though it's buried.

@Thommo9 what BMS are you actually running? That'll narrow it down considerably — some need a firmware flash before they'll handshake properly with the Growatt.

Had a similar headache when I was sorting comms between my Victron setup and a Fogstar Drift battery — BMS protocol mismatches are a genuine pain.

One thing nobody's mentioned yet: with the SPH series, make sure you've got the correct cable pinout for the CAN vs RS485 port. Growatt's own documentation is notoriously inconsistent between firmware versions, and I've seen people wire it correctly electrically but have the wrong protocol selected in the inverter menu — it just silently fails with no useful error.

Worth grabbing the ShineTools app and checking what protocol the inverter is actually broadcasting, rather than assuming it matches what's documented. Saved me hours when I was commissioning my garden office setup.

@MrBodge65 makes a fair point on baud rate — 9600 vs 115200 has caught people out more than once.

Good thread. Quick question for @SolarOwen and @MrBodge65 — once you'd got the BMS comms sorted properly, did the Growatt actually honour the charge/discharge limits being pushed from the BMS, or did you still need to manually constrain those parameters in the inverter settings as well?

Asking because I've got a Fogstar Drift 200Ah in my static caravan setup and I think comms are working (ShinePhone shows battery SOC at least), but I'm not 100% convinced the SPH is actually respecting the BMS charge current limits under load. Feels like it might be ignoring them and just doing its own thing based on the inverter-side settings instead.

Anyone actually verified this with a clamp meter rather than just trusting the display figures?

Not directly relevant to Growatt but might help someone — when I was sorting my static caravan setup I had constant grief with protocol mismatches until I actually rang the battery supplier directly rather than relying on the manual. Sounds obvious but the manual for my cells was just... wrong. Wrong baud rate listed, full stop.

@LisaStewart71 — on your question about SOC accuracy post-comms fix, in my experience yes it settles down considerably once the inverter is actually reading the BMS properly rather than guessing. Before I had comms working mine was doing this weird thing where it'd show 80% then suddenly cut to 20%. Proper comms sorted it almost immediately.

Worth checking if your SPH firmware is current too — Growatt pushed an update a while back that apparently improved third-party BMS compatibility.