Ignore AC1 80-20%

Running a pair of Quattros on my static caravan setup and the 80/20 charge limits on the lithium are doing my head in when the AC1 input keeps getting ignored mid-cycle! 🔋

Anyone else found their Lynx BMS occasionally just... deciding rules don't apply today? Mine acts like a teenager who's been told to tidy their room — acknowledges the instruction, then carries on regardless.

Specifically wondering if anyone's tweaked the ESS assistant settings to force the system to actually respect the configured SOC limits when AC1 is available, rather than letting the Quattro do whatever it fancies. I've read the Victron docs three times and I'm fairly certain they were written specifically to confuse people like me.

My current bodge involves:

• Setting DVCC charge current limits manually via the Cerbo
• Double-checking the VE.Configure assistant stack order (because apparently order matters, who knew)
• Questioning all my life choices

Using Fogstar cells elsewhere on site and honestly they're far less dramatic about the whole thing.

Is this a firmware gremlin, a config issue, or just the universe punishing me for going off-grid in the first place? Would love to hear from anyone running similar split-phase-style UK setups — I know true split-phase is more of a US thing but some of us are doing creative things with dual inverters over here.

Drop your configs below, genuinely curious how others are managing this! 👇

KarenEvans replied:

@HeatherWalker Oh I feel your pain with this one! Had exactly the same issue on my Victron setup last summer.

The thing that sorted it for me was checking the ESS Assistant configuration — specifically whether "Keep batteries charged" mode was conflicting with your charge limits. Also worth double-checking your MultiPlus-II (or Quattro) firmware is fully up to date, as there were some AC1 input detection bugs in older versions.

One thing people often miss: if your BMS is sending a charge current limit via DVCC that drops below the minimum threshold, the Quattro can effectively ignore the AC input entirely rather than taper down gracefully.

Have a look in VRM at your DVCC logs around the time it drops out — usually tells you exactly what's triggering it. What BMS are you running? That might help narrow it down! 🔌

Titch replied:

@HeatherWalker Classic Quattro behaviour this — the AC1 input gets deprioritised when the BMS comms are asserting charge limits via DVCC. What's happening is the system sees the 80% SoC ceiling, throttles the charger, and then gets confused about why AC1 went quiet mid-cycle.

Check your DVCC settings in VE.Configure — specifically whether SVS (Shared Voltage Sense) is enabled. If you're running Fogstar or similar LiFePO4 with a CANbus BMS, the voltage data from the battery is overriding what AC1 is reporting and essentially telling the Quattro "we're done here, mate."

Also worth checking your ESS Assistant version — older builds had a known quirk where AC1 ignore behaviour triggered prematurely at the absorption threshold.

What firmware are you running on the Quattros? That narrows it down considerably — there were some significant DVCC fixes post v2.80.

ExFirefighter11 replied:

@HeatherWalker Had this exact scenario on my boat install — pair of Quattros feeding a Fogstar Drift lithium bank. What caught me out was the charge current limit signal from the BMS dropping below the Quattro's minimum threshold, which the inverter interprets as "stop using AC1" rather than "slow down."

Check your DVCC settings in VRM — specifically SVS and SCS enabled with a sensible minimum charge current floor set. I'd also look at whether your BMS is sending a hard disconnect rather than a tapered current request near the 80% boundary.

On my shepherd's hut setup I ended up programming a slightly wider absorption window in the Quattro's charge curve so it doesn't hit that ceiling so abruptly. Effectively smooths the transition before the BMS gets twitchy.

What firmware are you running on the Quattros?

ExFirefighter42 replied:

Worth checking your DVCC settings in VE.Configure — specifically whether SVS (Shared Voltage Sense) is enabled alongside your BMS comms. When the Quattros are networked via VE.Bus and the BMS is asserting charge limits, the AC1 input can appear "ignored" but it's actually the system correctly honouring the BMS's CHARGE_DISABLE or reduced current requests.

On my motorhome setup with a single Quattro and Fogstar Drift cells, I found the ESS Assistant charge current limit was fighting the BMS signal — both trying to control the same parameter simultaneously.

Try logging via VRM for a few cycles and watch the Max charge current vs actual AC1 draw. If they diverge sharply at the same point each time, you've got a comms conflict rather than an AC1 switching issue.

What BMS are you running — proprietary or a third-party unit?

CrafterSolar replied:

@HeatherWalker One thing nobody's mentioned yet — check your AC Input Current Limit isn't being overridden by the ESS assistant. If you've got ESS configured alongside DVCC, they can fight each other over who's controlling charge behaviour, and AC1 gets the short straw.

In VE.Configure, look at your ESS mode settings specifically. Mode 3 tends to behave better with strict 80/20 limits on LiFePO4 in my experience.

Also worth checking: is your BMS actually sending a Charge Current Limit signal back via the GX device? I had similar headaches on my backup setup until I confirmed the CCL signal was actually being received — you can verify this in the Victron GX console under the battery menu. Sometimes the comms look fine but the value isn't propagating properly.