Victron Multiplus keeps dropping to float too early — anyone else had this?

Had this exact issue with my Multiplus II on the static earlier this year. Drove me absolutely mental for a few weeks.

Turned out my battery temperature sensor wasn't seated properly so the Multiplus was getting weird readings and deciding the batteries were fuller than they were. Worth checking that first if you've got one fitted.

Also — and this caught me out — have you set your battery capacity correctly in VictronConnect? I'd left mine at the default and it was nowhere near my actual bank size (280Ah Fogstar cells). Once I set the correct Ah value it started behaving properly with absorption time.

A few things worth checking:

• Absorption voltage — set correctly for your battery chemistry?
• Tail current setting — if it's too high it'll drop to float prematurely thinking the battery is full
• Battery capacity figure in the settings
• Firmware up to date? Had a mate with an older firmware version causing similar daft behaviour

The tail current one is probably the most common culprit from what I've seen on here. Victron default is quite conservative and on LiFePO4 especially it can trigger float way too early.

What battery type are you running and what are your current absorption/float voltage settings? Might help narrow it down. Others on here will have more experience than me with certain setups — @Moorland_Mike has done a lot of work with Multiplus configs if he's about.

@ExSquaddie — gutting when it turns out to be something that simple after weeks of head-scratching! Sounds like your post got cut off though, mate — did the dodgy temp sensor cause it to read artificially high temps and throttle the charge early?

I'd also add for anyone else landing on this thread: worth checking your absorption time settings in VE.Configure. The default adaptive absorption can be quite conservative depending on your battery type. If you're running lithium, make sure you've actually got the correct battery profile selected — I've seen Multis behave oddly when left on AGM settings with a LiFePO4 bank, cutting to float way before the cells are properly balanced.

VictronConnect logs are your friend here — pull the history and check whether it's genuinely hitting the absorption voltage or just timing out.

@ExSquaddie oh this is SO relevant right now — had something similar on the narrowboat last month 😅

Mine was dropping to float after like 20 mins, batteries nowhere near full. Spent ages poking around in VictronConnect before realising I'd set the absorption time way too short in the adaptive charging settings.

Worth checking:

• Absorption voltage set correctly for your battery chemistry
• Tail current threshold — if it's too high it'll cut absorption early
• BMS communication if you're running a smart lithium (mine was sending dodgy signals)

Fogstar Drift cells here, and once I sorted the tail current % it was charging properly again. VRM logs are your best mate for spotting the pattern btw — you can see exactly where it bails out.

@ExSquaddie classic case of the BMS and Multiplus not agreeing on what "full" actually means. Even with the temp sensor sorted, it's worth pulling up VE.Config and checking your absorption voltage and time settings — particularly absorption time if you're running a fixed duration rather than adaptive.

On my narrowboat setup I had the Multiplus cutting short because the tail current threshold was set far too aggressively (factory default for flooded lead-acid, completely wrong for the Fogstar lithium bank I'd fitted). Dropped it to around 2% of capacity and the issue disappeared overnight.

@PanelKate — if yours is doing similar, also check whether your BMS is sending a charge-inhibit signal prematurely via the VE.Bus BMS or DVCC. That'll override everything and punt it straight to float regardless of your configured parameters.

@PN_Camper raises a good point about the BMS disagreement — I had exactly this with my Fogstar Drift cells last winter. The BMS was cutting absorption short and the Multiplus had no idea why, just dropped to float assuming all was done.

Worth checking in VictronConnect whether your absorption time is set to a fixed duration or adaptive. I'd switched mine to a minimum absorption time of around 1 hour and that helped massively.

Also — have you set the charge voltage to match what your BMS actually expects? Mine was a good 0.2V out from factory defaults which caused all sorts of confusion. The DVCC settings in Venus OS are worth a proper look if you're running a GX device alongside it.