Repeatable ESS/DVCC bug: SmartSolar MPPT remains limited until AC load changes

Been seeing something odd with my setup that I reckon others might have hit too.

Running a Cerbo GX with a SmartSolar MPPT 250/85 on VE.Can, paired with a MultiPlus-II 48/5000. Since enabling ESS with DVCC properly configured, I've noticed the MPPT seems to get "stuck" at a reduced output ceiling — sometimes sitting at 30–40% of what the panels should be delivering — and it just stays there.

The weird part? If something kicks in on the AC side — kettle, washing machine, anything that shifts the load meaningfully — the MPPT suddenly wakes up and ramps to where it should be. Like it needed a poke.

Doesn't matter whether I'm on Venus OS 3.73 or 3.75, same behaviour both times. Fogstar Drift cells with a JK BMS pushing charge limits via DVCC, so I initially thought it was a BMS comms issue, but the reported CCL looks fine throughout.

A few things I'm curious about:

• Anyone else seen the MPPT stay artificially limited until an AC event "resets" it?
• Could this be a CVL/CCL handshake timing issue between the BMS and the Cerbo?
• Is there a known workaround beyond just waiting or triggering a load change manually?

Feels like a race condition somewhere in how ESS arbitrates between the inverter demand and the MPPT output — but I'm no firmware dev. Would be good to know if this is widespread or just my particular combination of kit. Victron community thread has a few replies but nothing conclusive yet.

@CableTieWarrior classic Victron "it's not a bug, it's an undocumented feature" energy here 😄

Few things worth ruling out before diving deep:

• What firmware are you on? Cerbo GX v3.x had some DVCC quirks that were patched
• Is your BMS talking to the

@CableTieWarrior this rings a bell from when I was commissioning my shepherd's hut system last autumn. What firmware is your Cerbo on? There was a known DVCC/ESS interaction issue where the SVS (Shared Voltage Sense) was fighting the MPPT's internal sense, causing the charge current limit to latch incorrectly until something forced a recalculation — an AC load change being exactly the kind of event that would trigger that.

Worth checking in VRM: is your DVCC > Charge Current Limit showing a stale value just before the load event clears it?

Quick things to try:

• Disable SVS temporarily, observe behaviour
• Confirm VE.Can termination resistors are seated properly (causes subtle comms glitches that look like ESS logic bugs)
• Check MPPT and Cerbo are on matching recommended firmware — Victron's compatibility matrix matters here

What does ESS > BatteryLife state show during the limited period?

@CableTieWarrior this is almost certainly the ESS assistant's DVCC current limiter not releasing after a CV absorption phase completes. I saw identical behaviour on my boat install — MultiPlus-II 48/3000 with a SmartSolar 150/45 on VE.Direct.

The trigger for me was the SVS (Shared Voltage Sense) and SCS (Shared Current Sense) flags on the Cerbo not agreeing fast enough with the MPPT's own internal state. The AC load change forces a recalculation cycle that effectively kicks the limiter loose.

Worth checking:

• VRM diagnostics → confirm MPPT charge current limit value is sitting artificially low between events
• Disable SVS temporarily and see if the limiting persists
• Check ESS mode is set correctly under the DVCC menu — Keep batteries charged behaves very differently to Optimised

@WattEd firmware version matters enormously here — v3.10+ changed how DVCC arbitrates between connected chargers.

@LakelandNomad that DVCC limiter theory is interesting — I saw something similar on my narrowboat install last year but couldn't pin it down properly at the time.

One thing nobody's mentioned yet: check your SVS (Shared Voltage Sense) settings. On VE.Can setups I've found SVS can occasionally cause the MPPT to receive a slightly elevated voltage reading, which keeps it thinking it's further into absorption than it actually is. Net effect looks identical to what you're describing.

Worth logging Venus OS for an hour and watching mppt_charger_voltage_sense vs actual battery voltage — if they diverge by even 50-100mV during the stuck period that'd point squarely at SVS rather than the DVCC limiter itself.

Running Fogstar Drift cells here so my BMS comms are via VE.Can too — happy to compare configs if it'd help narrow it down.

@LakelandNomad's DVCC limiter theory tracks with what I've seen on my own setup. The bit nobody's mentioned yet: check whether your MPPT is actually receiving the updated CCL from the BMS after the AC load shift, or whether the Cerbo's just re-broadcasting a stale value. On VE.Can you can watch this in real-time via the GX console — DVCC → Maximum Charge Current. If that figure stays frozen while your actual solar output is artificially capped, that's your culprit, not the MPPT firmware itself.

Had this drive me absolutely mental for three weeks before I spotted the Cerbo was caching an old CCL value post-absorption. Factory reset of the comms priorities sorted it on my end, though I appreciate that's a nuclear option.