With or Without JK BMS Comms SRNE Inverter Not Reaching full Absorb Voltage (57V)

Been following this one with interest because I had something similar on the boat last winter with my SRNE hybrid and a JK BMS combo.

What I found — and this might not be your exact issue — is that the SRNE's own charge profile was fighting the BMS. Even with comms disconnected, the inverter seemed to be hitting its own internal voltage ceiling before the JK's CVL kicked in. Worth checking what your SRNE's battery voltage setting is actually configured to under the basic charge params, not just the CAN/RS485 side.

A few things worth ruling out:

• Cable voltage drop between inverter and battery — at higher currents this can be significant, and the inverter "thinks" it's hit absorb when the cells haven't
• JK firmware version — some older versions were a bit sketchy with the CVL values they were broadcasting
• Whether your SRNE is set to Lithium (self-defined) vs a preset — the presets on mine were garbage

What inverter model specifically? The SRNE MH series behaves differently to the ML range in my experience.

Also curious whether others here have had luck using the Victron approach of just ditching comms entirely and letting the BMS handle cutoff via a relay — sometimes the simplest solution wins.

Anyone else running JK + SRNE who's cracked this? Feels like there should be a definitive answer by now but I keep seeing the same thread pop up every few months.

@RKE_Builds interesting timing, I've been chasing something almost identical on my garden office setup with an SRNE and JK combo.

One thing worth checking that doesn't get mentioned much — the SRNE's "battery type" setting. If it's left on AGM or a generic lithium preset rather than "user defined", it'll internally cap the absorb target regardless of what the BMS is telling it over comms. The comms voltage can be perfect but the inverter quietly overrides it.

Set it to user-defined and manually enter your cell parameters. My 16S LiFePO4 pack was sitting at ~55.8V absorb when it should've been hitting 57.6V — turned out to be exactly this. Fogstar cells, Victron cabling, JK BMS, and the SRNE was just ignoring the lot due to a preset conflict.

Worth five minutes before pulling the comms cable out entirely.

Lurked on this thread for a while before jumping in, but this rings a bell from when I was commissioning my shepherd's hut system last spring.

I had the SRNE stubbornly refusing to hit target absorb voltage — turned out the issue wasn't the BMS comms at all. The inverter was seeing a phantom load spike during the absorb phase and quietly throttling back to protect itself. Completely silent about it in the logs.

Worth checking whether your AC loads are doing anything funny right at that transition point. In my case it was a small fridge compressor kicking in at the worst possible moment.

@VoltWill — curious whether your garden office has anything cycling on/off around the same time the voltage flattens out?

Not saying it's definitely the same cause, but it's an angle worth ruling out before diving deeper into the BMS comms rabbit hole.

Worth checking your AC input voltage compensation settings in the SRNE — there's a parameter buried in the advanced menu that trims the charge voltage based on incoming AC quality. If it's seeing any fluctuation on the grid side it can quietly back off the absorb target without logging it obviously anywhere.

Also had a weird one on my narrowboat where the battery temp sensor placement was causing the SRNE to apply temperature derating even in mild conditions. Moved the sensor away from the BMS heat spreader and suddenly absorb voltage jumped back up to where it should be.

@VoltWill the garden office setup — are you on split phase or single phase input? That sometimes matters with how SRNE handles voltage regulation internally.

@HeatherSoul ooh which parameter number is that buried under — mine's got about 400 menus and I've definitely accidentally set my static caravan's Victron to charge at 3V once by fat-fingering something at midnight 🫠

Also on the original issue — have you confirmed your battery cable voltage drop isn't eating into that headroom before the SRNE even sees 57V? My Fogstar Drift cells were showing 56.4V at the BMS but the inverter terminals were reading properly, turned out to be a dodgy crimp on the negative that was introducing just enough resistance to confuse everything.

Boring answer but: measure at the inverter terminals directly rather than trusting the BMS reported voltage, they can be surprisingly far apart.