Assistance needed with PowMR Inverter and Pylontech Fidus Plus Battery

Had a similar headache getting my cabin setup talking to a third-party inverter a while back — the comms protocol mismatches are a genuine nightmare.

With PowMR specifically, the CAN bus implementation can be a bit loose compared to what Pylontech expects. The Fidus Plus wants to handshake properly before it'll let the inverter draw anything meaningful, and if the inverter is sending the wrong battery type code, the BMS just sits there sulking.

A few things worth checking:

• DIP switch settings on the Pylontech — make sure you've got the right master/slave configuration if you're running more than one unit
• Baud rate on the CAN port — 500kbps is standard for Pylontech but some PowMR units default differently
• Battery type selection in the PowMR menus — there's usually a "Pylontech" or "Lithium CAN" option buried in there, sometimes labelled oddly

Honestly, I eventually jumped ship from a budget inverter to a Victron Multiplus for my static caravan and the difference in how cleanly it negotiated with the battery pack was night and day. The DVCC settings in VenusOS just sorted everything out automatically.

That said, plenty of people do run PowMR with Pylontech successfully — it usually just takes some patience with the settings. Would be useful to know which firmware version your PowMR is on, as there were some known comms bugs in earlier builds.

Anyone else on here running this particular combo? Would be good to pool knowledge on it.

@SparkySparky interesting point about the CAN bus — is the PowMR actually expecting the full Pylontech protocol or a simplified version? I've been reading that some of the cheaper inverters claim Pylontech compatibility but are only really designed around the older US2000 series rather than the newer Fidus Plus.

Has anyone tried forcing the battery type selection to a generic lithium setting and just letting the BMS handle protection independently? I'm wondering if that sidesteps the comms issue entirely, even if you lose some of the smarter charge curve integration.

Also — what firmware version is the PowMR running? I've seen mentions on here of certain versions having known CAN handshake bugs. Might be worth checking if there's an update before going too deep into cable pinout troubleshooting.

@George1972 PowMR typically wants the Pylontech RS485 protocol not CAN, so check your battery's DIP switches are set to RS485 mode — Pylontech Fidus Plus defaults to CAN out of the box, which is why everyone's pulling their hair out.

Quick checklist:

• DIP switch 1 on the Fidus Plus → flip to RS485 mode
• Use the RJ45 port on the battery, wired to the inverter's BMS comms port
• Set PowMR battery type to "Lithium" then select "Pylontech" in the protocol menu
• Baud rate: 9600

If it still won't handshake, there's a known firmware revision on some Fidus Plus units that breaks third-party comms — worth checking Pylontech's site for the latest flash.

Had a similar faff getting my motorhome Victron setup talking nicely — comms issues are always the last 10% that takes 90% of the time.

@MarineGeoff is right on the RS485 point — and worth adding that the Fidus Plus DIP switch config for Pylontech emulation mode is usually 00001 but I've seen batches where it's 00010, so don't trust the manual blindly.

Also double-check your A/B wiring polarity on the RS485 cable itself — PowMR inverters are notoriously fussy and will just silently ignore the battery rather than throw a proper fault code, which'll have you chasing ghosts for days like I did in my motorhome build before I realised I'd swapped the pair.

Victron would've told you exactly what was wrong — just saying. 😑

@FormerCop @MarineGeoff — right, so RS485, Pylontech protocol, DIP switches. Got it.

Here's the thing nobody mentions until you've already spent a Saturday evening squinting at a wiring diagram with a torch in your teeth: the cable pinout between PowMR and third-party batteries is frequently crossed, not

@AZY_Marine what nobody mentions is the baudrate mismatch — caught me out completely on my van build. PowMR defaults to 9600 but some Fidus Plus units ship expecting 19200.

You'll get what looks like a successful comms connection (the inverter stops throwing error codes) but the SOC readout is completely fictional. Mine was reporting 87% whilst the Fogstar cells were practically gasping. Found out the hard way when I nearly flattened the pack overnight.

Dig into the PowMR LCD menu — it's buried about six levels deep under something unhelpfully named "Battery Parameters" — and force the baudrate to match whatever your Fidus is actually broadcasting.

Worth sticking a multimeter on the RS485 lines whilst it's chatting too, just to confirm there's actual traffic happening rather than optimistic silence.