Node-RED flow to switch between 80% and 100% charge on a 24V lithium bank

Been meaning to sort this out on my boat for ages so this thread is timely.

I've got a 24V lithium bank (Fogstar Drift cells) running through a Victron Multiplus and I'm forever diving into VRM or the Cerbo GX touch screen to manually nudge the charge voltage before a longer trip. Absolute faff.

The DVCC max charge voltage approach makes a lot of sense — setting it to 28.0V for daily and bumping to 29.2V the night before a passage. Keeps the cells happy long-term without having to remember to dial it back afterwards.

Has anyone actually deployed a Node-RED flow on their Cerbo to handle this with a simple dashboard button? I'm thinking something like:

• Mode A → 28.0V (roughly 80%, daily cycling)
• Mode B → 29.2V (100%, pre-trip top-up)
• Maybe a timer to auto-revert after 8 hours?

The auto-revert bit feels important on a boat — last thing you want is forgetting to switch back and leaving it sat at 100% for days on end.

I've had a poke around the Venus OS Large flows that come stock but nothing quite does this out of the box. Feels like it should be a 20-minute job for someone who knows Node-RED better than I do.

Anyone already running something similar on a liveaboard setup? Would love to see the actual flow if you're willing to share. Screenshots or a JSON export would be brilliant.

@MandyGrant snap — I did almost exactly this for my shepherd's hut setup, though on a 12V bank.

The key with Fogstar Drift cells is getting the absorption voltage right for each mode. I've got a Node-RED flow that watches a time-of-day inject node and flips between two MQTT payloads hitting the Victron com.victronenergy.settings path:

• Daily charge: absorbV = 27.2 (roughly 80%)
• Pre-trip / weekend arrival: absorbV = 28.8 (100%)

I trigger the full charge manually via a dashboard toggle rather than a schedule — suits my "am I heading out this weekend?" lifestyle better than automation.

One gotcha: make sure your float voltage stays consistent regardless of mode, otherwise the BMS gets twitchy. Learned that the hard way watching my cells drift unevenly over a fortnight.

Really interested in this thread — I've been wrestling with a similar problem for EV charging at my cabin.

Quick question for anyone who's got this working: does the Node-RED flow need to run on a Cerbo GX, or can it sit on a separate Pi and still talk to the Multiplus via MQTT?

I'm not sure I want to rely on the Cerbo being the brain for something that runs automatically overnight. Also, does the flow need to handle the absorption/float distinction separately, or does just adjusting the charge voltage ceiling via the DVCC settings handle all of that automatically?

@MuddyNomad curious whether your 12V setup had any quirks with the Drift cells specifically — I've heard they can be fussy about the exact absorption voltage threshold compared to other lithium chemistries.

@MandyGrant done exactly this for my garden office — Node-RED flow with a simple dashboard toggle button that writes the absorption voltage via MQTT to the Victron CCGX, 28.8V for "storage mode" vs 29.2V for "full beans mode" — took me three attempts and one very confused Multiplus but it works a treat now 🎉

Great thread, this has been on my to-do list for my narrowboat setup too.

One thing worth adding — if you're using the MQTT path to write to the Multiplus via Venus OS, double-check you're writing to the correct com.victronenergy.settings path rather than directly to the device service. Caught me out for a good afternoon of head-scratching.

Also @MandyGrant, with Fogstar Drift cells specifically, I'd suggest adding a small delay node (30 seconds or so) after the toggle before the write executes. Means accidental button presses on the dashboard don't immediately hammer the charger with conflicting instructions. Belt and braces really.

@OffGridFreak the EV charging use case is slightly different — you'll likely want a time-based trigger rather than a manual toggle, worth starting a separate thread if you want to dig into that properly.