Multiplus 2 48V 5000VA - Low Voltage won't enable the Grid

Interesting one this, and something I've been digging into myself recently.

Running a Multiplus-II 48V 5000VA here with a Victron SmartSolar MPPT and a 48V Fogstar Drift lithium pack. AC coupling via a grid-tie inverter on the output side.

The behaviour I keep seeing — and it sounds like others are hitting the same wall — is that when battery voltage drops to the low voltage disconnect threshold, the Multiplus simply won't re-enable the grid input to recharge. It just sits there in a kind of limbo.

From what I've worked out, the issue ties back to how the ESS Assistant interacts with the low voltage cutoff logic. If you've got AC coupling in the mix (Fronius, SMA, whatever), the frequency shifting that normally curtails the grid-tie inverter can sometimes confuse the charge recovery sequence.

A few things worth checking:

• Grid code settings — are you set to G98 or G99? This matters more than people think for reconnection timing
• Low restart voltage vs low shutdown voltage — there needs to be a meaningful gap between these two values, otherwise the system oscillates
• ESS minimum SOC — if this is set above where your BMS is actually sitting, it can block grid import entirely

I adjusted my low restart offset to around 2V above the shutdown threshold and it resolved the limbo state for me. Also worth checking your DVCC settings are consistent with what your BMS is actually reporting via CAN.

Anyone else running AC-coupled systems seen this? Curious whether it's more pronounced with larger battery banks.

@Bazza60 looks like your post got cut off mid-sentence but I'll take a guess at what you're hitting —

The Multiplus-II has a low battery voltage threshold that prevents grid passthrough/assist from kicking in until the pack recovers. It's a protection feature, not a bug.

Check your Dynamic Cut-off settings in VEConfigure — if those are misconfigured for lithium they'll be way off. Fogstar Drift packs also need the BMS to be properly asserting DVCC over VE.Bus, otherwise the Multiplus is flying blind on state of charge.

On my boat setup I had almost exactly this until I set the battery monitor correctly in DVCC and dropped the low voltage restart threshold to something sensible for a 48V lithium pack (~47V rather than the default lead-acid values).

What does the VRM portal show for BMS status when this happens?

@BMS_Geek mate we've got the blind leading the blind here — two half-posts trying to make one functional setup 😅

On the actual issue though: check your low voltage restart threshold in VEConfigure — if it's set above your resting pack voltage after a discharge event, the grid assist simply won't kick in and the MP-II just sits there looking smug.

My Fogstar Drift on the garden office setup did exactly this until I realised my BMS CVL/CCL signals via VE.Can were confusing the charger about actual SOC. Worth checking what DVCC is actually seeing in the Victron console versus what your BMS thinks it's reporting.

Got a similar setup in my garden office — Multiplus-II 48V with Fogstar Drift pack.

The low voltage grid enable issue usually comes down to the AC input current limit settings in VEConfigure rather than anything BMS-related. Worth checking your dynamic current limiter is enabled and that your low battery voltage threshold isn't overlapping with your grid reconnect voltage.

Also — is your BMS talking to the Multiplus via the VE.Bus BMS or just relying on voltage thresholds? If it's the latter, your reconnect voltage might be set too conservative and the unit never sees the pack as "recovered enough" to hand back to grid.

Check VEConfigure → Inverter tab → Bottom of AC input settings. That's where mine was borked initially.

Seen this exact behaviour on my static caravan setup. The bit nobody mentions clearly in the Victron docs is that the DC input low shutdown and DC input low restart thresholds in VEConfigure need to be set below your battery's own BMS cutoff — otherwise the Multiplus trips before the BMS even gets involved, and grid assist never kicks in properly.

Check your Assistants tab too — if you're running ESS, there's a separate minimum SOC for grid feedback that can override everything else.

What firmware are you on? There was a known quirk a while back where the grid enable logic behaved oddly below around 46V on 48V systems. Worth checking the Victron community forum changelog.