Multiplus 2 3000 GX with sunwaytech 5.22kwh battery

Interesting setup — curious how this pans out for others running the Multiplus 2 3000 with non-Victron batteries.

I went through something similar last year. Had a budget all-in-one inverter-charger that couldn't regulate charging properly — basically hammering the batteries at full current regardless of state of charge. Ended up killing a set of cells faster than they should've gone.

Switched over to a Victron Multiplus-II and honestly the difference in charge control is night and day. The absorption and float stages are properly managed, and you can tweak everything through VE.Configure. That flexibility is massive if you're running a battery that doesn't have native Victron comms.

With the Sunwaytech packs specifically — has anyone got proper BMS communication working? That's where things get interesting. Without a CANbus or RS485 link between the battery and the Multiplus/GX device, you're essentially flying blind on cell-level data. The GX will show you overall voltage and current, but the BMS won't be able to assert charge limits dynamically.

If you're going down this route I'd strongly recommend:

• Setting conservative charge voltage limits manually in VE.Configure
• Using DVCC on the GX if you can get any comms established
• Keeping an eye on cell balance through whatever the Sunwaytech app offers natively

The Multiplus 2 3000 is a brilliant bit of kit but it won't babysit a battery that isn't talking back to it properly.

Would be good to hear from anyone who's managed to get Sunwaytech working cleanly with Victron — there's not much documented on UK installs specifically.

@CallumCampbell55 Budget all-in-ones are basically the dark souls of off-grid — everybody suffers through them before finally caving and buying Victron like a proper adult.

@DailyWanderer nailed it, and the Sunwaytech pairing with the Multiplus 2 is genuinely one of those "will it blend?" moments — spoiler: it usually does, once you've wrestled the BMS comms into submission via a USB-to-RS485 adapter and enough swearing to power a small village.

Running a similar non-Victron battery in my garden office setup and the secret sauce is just manually configuring the charge/discharge limits in VictronConnect rather than relying on DVCC to figure it out automagically — because it won't, bless its cotton socks.

@CallumCampbell55 Worth flagging — if the Sunwaytech doesn't have a supported BMS protocol (CAN or VE.Bus BMS comms), the Multiplus 2 won't get proper battery data and you'll be flying blind on cell-level protection. You'd need to manually configure the charge parameters and set conservative voltage limits yourself.

Check whether it's speaking DVCC properly in VictronConnect. If the BMS isn't handing off SOC and cell data, your charge algorithm is essentially guesswork.

Had a similar issue pairing a non-Victron LiFePO4 with my setup — ended up having to lock down the absorption voltage and disable the built-in charge algorithm entirely, just running it as a dumb charger with tight limits. Not ideal but it works reliably.

What firmware version is the GX on? Some of the DVCC handling improved significantly post 2.90.

@WhatsAFuse65 raises the critical point. I'd add that even if Sunwaytech claims CAN BMS compatibility, verify which specific protocol variant — Victron's DVCC implementation expects particular charge/discharge limit messages, and generic CAN profiles often don't map cleanly. Had this exact issue with a third-party battery on my static caravan setup before I moved to something with a properly documented protocol.

Worth checking the Victron Compatible Battery list on their website first. If it's not listed, you're essentially in "managed battery without management" territory — the Multiplus will operate, but you lose proper SoC visibility and charge curve control in VRM, which defeats half the point of the GX integration.

Can also cause issues with low-temp charge cutoff if your site is exposed over winter.