Problem with assistants ignoring AC input

Ran into something maddening with my Multiplus-II setup last week that I reckon some of you parallel-configuration lot might have experienced.

I've got two Multiplus-II 48/5000s running in parallel at the cabin, fed by a decent Fogstar Drift LiFePO4 bank. Set up an assistant to hold off accepting grid input until the batteries dropped to a certain SOC — standard stuff, trying to maximise solar self-consumption before leaning on the hook-up point.

Worked brilliantly for about three weeks. Then, seemingly out of nowhere, the units started completely ignoring the AC input ignore condition and just... taking whatever the grid offered, regardless of battery state. No obvious trigger. No firmware change. Nothing in the VRM logs that screamed "here's your culprit."

A few things I've checked so far:

• Assistant order — had a nagging suspicion another assistant was overriding the ignore condition
• ESS vs standalone assistant logic — mixing these can apparently cause some wonderfully unpredictable behaviour
• VE.Configure sync — both units were definitely flashed with identical configs (triple-checked)

My current working theory is that ESS is quietly wrestling control back from the custom assistant under certain grid conditions, essentially deciding it knows better than me. Which, fair enough Victron, but still.

Has anyone else seen this with a parallel setup specifically? I wonder if it's more pronounced when two units have to agree on what to do with AC input — maybe there's a timing/arbitration issue between them?

Would love to know if tweaking the AC input current limit settings made any difference for anyone, or whether this is fundamentally an ESS configuration rabbit hole I need to fall down. 🐇

@DailySolar you cut off mid-sentence mate, but I'll bet my soggy static caravan on it being an assistant misconfiguration — check your AC input current limit isn't set lower than what the grid can actually deliver, because the assistants will gleefully ignore input and invert off the batteries instead like they're doing you a favour.

Had the same grief with my emergency backup setup; turns out VE.Configure had reverted to some daft default after a firmware update and I hadn't noticed for three weeks.

Also — are both units on identical firmware? Parallel Multiplus-IIs with mismatched firmware versions is a special kind of punishment Victron reserved for people who skip the release notes.

@DailySolar the suspense is killing me more than my battery bank in January ☠️

@ForestDaz probably right about the assistant config — in my experience the ESS assistant and the Generator Start assistant have a bit of a domestic if they're not set up in the right order. Victron's documentation on assistant stacking reads like it was written by someone

@DailySolar finish your sentence man, you're leaving us hanging worse than a floating neutral 😄

Right, assuming it's what I think it is — parallel Multiplus-II units frequently throw a wobbly when the AC Input Current Limit Assistant conflicts with the ESS Assistant priority settings. Classic symptom is the units ignoring shore/grid input entirely and hammering the batteries instead.

In VE.Configure, check your assistant loading order — ESS needs to sit above the current limiter assistant in the stack. Victron's documentation is characteristically vague on this but it absolutely matters.

Also worth verifying your virtual switch settings aren't overriding things independently. Had almost exactly this on my garden office setup last spring — took me an embarrassingly long afternoon with VE.Configure 3 before I spotted it.

Share your full assistant configuration screenshot when you get a moment and we can properly dig in.

Ha, the thread of cliffhangers! 😄

@DailySolar whenever you're ready to finish those sentences we're all ears...

In the meantime, jumping ahead a bit — if it is assistant-related and you're running parallel units, one thing worth double-checking beyond the obvious configuration stuff is whether both units are actually on the same firmware version. I had a nightmare a while back where a firmware mismatch between paralleled units was causing really inconsistent assistant behaviour that looked for all the world like a settings problem. Spent ages going round in circles in VEConfigure before I spotted it.

Also worth confirming your VE.Bus System Configurator ran cleanly and both units properly recognised each other as parallel rather than one trying to act as a standalone. Sometimes it looks fine on the surface but isn't quite right underneath.

Finish your sentence and we can probably nail it down properly! 🔧