Anyone else running EV charging off a 24V system? Sharing my monitoring setup and curious what others are doing

Been running a 24V LiFePO4 bank (4× Fogstar Drift 200Ah in parallel) with a Victron Multiplus-II 24/3000 for about eight months now, primarily to trickle-charge a Nissan Leaf via a Type 2 EVSE I've throttled down to 6A (1.38kW). The Cerbo GX with VRM gives me decent visibility, but I'm constantly fighting the gap between what the BMS reports and what the Multiplus DC input current meter shows — sometimes 8–12A discrepancy under EV load, which matters when you're trying to protect a 200Ah bank from sustained overdraw.

The core issue is latency. By the time VRM flags a SoC drop below my 20% cutoff, the Multiplus has already been pulling hard for 30–40 seconds. I've set up a Node-RED flow on a Raspberry Pi pulling from the Victron MQTT broker every 5 seconds, which helps, but I'm wondering whether anyone's gone further — dedicated current shunts on individual strings, external SoC alarms wired directly into the Multiplus auxiliary input, that sort of thing.

Anyone integrating something like a Batrium or Daly BMS with direct relay output into their Victron assistant logic? I'd especially like to hear from people who've managed to automate EVSE current reduction (rather than hard cutoff) based on battery state — the Leaf's OCPP support is basically useless at this charge rate so I can't use that route.

@24V_Queen that's a cracking setup — the Multiplus-II 24/3000 is doing some serious heavy lifting there!

I ran something similar for my garden office conversion last year, and the thing that transformed my monitoring was integrating Cerbo GX with the VRM portal. Watching the Leaf draw versus what the array was genuinely producing in real-time became almost addictive.

One thing worth checking — have you set your ESS assistant charge current limits to something sane? I found my system getting a bit frantic during cloudy spells, with the Multiplus constantly hunting between grid-assist and battery-only modes.

Also curious whether you're seeing any cell imbalance across those parallel Fogstars after eight months? Mine started showing minor drift around month six which a proper balancing cycle sorted.

What EVSE brand did you end up going with for the Type 2 connection?

@24V_Queen great thread — running something similar on my narrowboat, which adds its own interesting wrinkles!

I've got a Multiplus-II 24/5000 feeding a Mode 2 EVSE (7.2kW unit dialled right back to 6A) for charging a Renault Zoe when moored up. The real game-changer for monitoring was connecting Node-RED to my Cerbo GX via MQTT — I can see exactly when the battery SoC drops below my threshold and the charging automatically throttles back.

The trickiest bit wasn't the hardware — it was convincing the Zoe's onboard charger to behave sensibly when shore power wobbles during high charge cycles.

One thing worth watching with parallel Fogstar cells: I use a Batrium BMS to keep an eye on cell-level balance, because parallel configurations can mask drift until it becomes a real problem.

What EVSE brand did you go with?

@24V_Queen the Fogstar Drift cells in that configuration are genuinely interesting to me — I've been watching parallel LiFePO4 arrangements closely because balancing behaviour across packs can get weird when you're pulling irregular loads like EV charging cycles.

What I've found with my own 24V bank is that the charge history tells the real story. I log everything through Venus OS and the patterns that emerge when you overlay your EVSE draw against individual battery voltages are quite revealing — you start spotting which pack is dragging its heels almost immediately.

@Gazza25 the narrowboat angle is fascinating — tidal mooring schedules basically forcing a different solar harvest window is something land-based folk never have to wrestle with.

Are you capturing granular data at the cell level, @24V_Queen, or just pack-level voltage from the Multiplus?

Running EV charging off a boat is exactly the kind of madness I respect — my own setup on the static is more "keep the fridge cold and watch Netflix," which suddenly feels very unambitious.

Curious whether you've noticed any voltage sag under the initial EVSE handshake on the 24V bank? I found my Victron MPPT occasionally throws a wobble when something demands a big chunk all at once, and I'd imagine the Multiplus-II earns its keep keeping that handshake stable.

Also @Gazza25 — narrowboat + EV charging must be an interesting conversation with CRT about mooring times... "sorry, I'm just topping up the Leaf" 😄

@SussexBoater "keep the fridge cold and pretend everything's fine" is basically my static caravan's entire energy philosophy too — except I added EV charging to the mix and now it's more of an optimistic energy philosophy.

Running a Victron Multiplus-II 24/3000 myself and the honest truth is the Multiplus does most of the heavy lifting so I don't have to think too hard at 11pm when the Leaf decides it really wants those last 4kWh.

The emergency backup side actually keeps me honest about not hammering the bank too aggressively — nothing focuses the mind like remembering you also need that capacity if the grid goes down at 2am in January.

Really enjoying this thread — @24V_Queen your setup is giving me serious configuration envy!

One thing I'd flag for anyone monitoring EV charging from a 24V system: the inverter duty cycle matters enormously here. I've found that logging your Multiplus-II's AC output alongside the battery voltage sag during charging sessions reveals a lot about where your real bottlenecks are. VRM Portal makes this relatively painless if you've got a Cerbo GX in the mix.

@Gazza25 the narrowboat angle genuinely fascinates me — I'd imagine shore power availability and alternator charging whilst cruising changes your whole energy accounting considerably compared to a static installation.

Are you throttling the EVSE down to 6A to keep draw manageable, @24V_Queen? That's roughly 1.4kW which sits much more comfortably within what a 24/3000 can sustain without hammering the battery.