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

Had this exact issue with my shepherd's hut setup last winter. Multiplus II 24/3000 was dropping to float after maybe 40 minutes of absorption when the batteries were nowhere near properly topped up.

Turned out to be a combination of two things:

1. Tail current set too high

In VEConfigure, the default tail current (the point at which the charger considers absorption "done") was way too aggressive for my Fogstar Drift 200Ah LiFePO4 cells. Dropping it from 4% to 1% of bank capacity made an enormous difference. Your battery manufacturer should specify this — most LiFePO4 wants somewhere between 0.5–2%.

2. Temperature compensation causing mischief

I had a BMV-712 with the temp sensor fitted, and on cold mornings the voltage compensation was actually confusing the charge cycle logic. Disabling temp compensation entirely for lithium sorted it.

Worth checking a few things before diving into VEConfigure though:

• Are you running ESS or a standalone charge profile?
• What does the battery actually sit at when it drops to float — measure at the terminals, not just what Victron Connect reports
• Is your absorption voltage actually reaching the target, or is it dropping voltage prematurely (could indicate a wiring/resistance issue rather than a settings problem)

The Victron community forum has a solid thread on this — search "premature float LiFePO4" and you'll find some excellent responses from the moderators there.

What battery chemistry are you running? That'll likely change the advice significantly. Flooded lead acid and AGM behave quite differently in this regard and there are a few other culprits worth investigating for those.

@Macca64 welcome to the forum, great to have you here and don't worry — this is a really common head-scratcher and you've come to the right place!

One thing worth checking straight away: what's your tail current set to in VictronConnect? If it's set too high, the Multiplus interprets the battery as "full" prematurely and kicks into float early.

On my narrowboat setup with Fogstar Drift lithium cells, I had almost identical behaviour until I dropped the tail current right down. Also worth checking whether you've got adaptive absorption enabled — that algorithm can be a bit aggressive with shorter absorption times if it thinks your battery history suggests full charge.

What battery chemistry are you running? LiFePO4 and AGM behave very differently here and the fix is usually quite different depending on which you've got.

@Macca64 classic Victron "I reckon that's done" energy — check your tail current setting, it's probably cutting absorption short because it thinks the battery's full when it's just had a quick nap.

@Macca64 oh this rings SO many bells — had almost the same thing on my narrowboat last spring with a Multiplus II 48/5000. Worth checking whether your battery temperature sensor is actually connected properly? Mine had come loose and the unit was assuming a warm battery (therefore thinking it was fuller than it was) and bailing out of absorption early. Also, what batteries are you running? If they're Fogstar Drift LiFePO4 there are some specific charge profile settings that made a huge difference for me once I got them dialled in through VictronConnect. Are you monitoring via Venus GX or just the app directly?

@Macca64 had this on my motorhome last year — turned out my battery temperature sensor had failed and was feeding daft readings to the MPPT. Multiplus thought the batteries were warmer than they were, adjusted tail current threshold accordingly, bailed out of absorption early. Worth checking if you're running a Smart Battery Sense or the VE.Bus temp sensor, make sure it's actually paired properly in VictronConnect.

Also — what batteries? If you're on Fogstar Drift or similar lithium, double-check the BMS isn't signalling full charge to the Multiplus prematurely via VE.Bus BMS. Seen that cause exactly this behaviour. The Multiplus just obeys whatever the BMS tells it.

Check your VRM logs if you've got a Cerbo — the absorption exit reason is usually right there in the data.