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

Had this exact issue last winter with my Multiplus-II 48/3000. It kept jumping to float when the batteries were nowhere near full — SOC was still showing 75-80% in VRM but the charger was convinced it was done.

Turned out my absorption voltage was set slightly too high relative to my actual battery chemistry. I'm running Fogstar Drift LiFePO4 cells and the default Victron profile wasn't quite right out of the box. Once I dropped the absorption voltage by about 0.2V and extended the absorption time, it started behaving properly.

A few things worth checking:

• Battery temperature — if your temp sensor is reading high, Victron compensates by cutting absorption short
• Tail current setting — this is the big one. If your tail current threshold is too generous, it'll assume the battery is full when it's not. Try dropping it to around 1-2% of your battery capacity
• BMS communication — if you're using DVCC with a smart BMS, conflicting charge parameters can confuse the Multiplus completely

Worth connecting via VictronConnect and watching the charge curve in real time rather than just relying on VRM. Sometimes the dashboard lags and makes it look worse than it is.

What battery setup are you running? LiFePO4 or lead acid makes a big difference to how you'd approach this. Also — are you on the latest firmware? There were some absorption/float transition bugs in older versions that Victron quietly patched.

Happy to share my exact config settings if it's a similar setup to mine. Others on here have probably got more experience with lead acid edge cases too.

Hey @Mark1978, classic symptom of the tail current threshold being set too aggressively. Worth checking your absorption end-trigger in VEConfigure — if "tail current" is enabled and set too high (say 4-5% of battery capacity), it'll cut to float prematurely even when the batteries aren't genuinely full.

Also worth asking: what battery chemistry are you running? If it's lithium with a BMS feeding SOC data via VE.Bus or CAN, there can sometimes be a conflict between what the BMS is telling the Multiplus and what VRM's own SOC calculation shows. The two can diverge quite significantly, especially after a partial cycle.

What does your absorption voltage look like in VEConfigure? If that's slightly low as well, you might be hitting tail current before the cells are properly balanced.

@ColPalmer has the tail current angle covered, so I'll add something slightly different — have you checked whether your battery temperature sensor is wired correctly? I had a similar issue on my static last winter with a 24/3000 and it turned out the BTS was giving spurious readings, which was causing the Multiplus to think the pack was warmer than it actually was and cutting absorption short.

Also worth cross-referencing your SOC reading with actual resting voltage. VRM SOC can drift if you haven't done a proper calibration cycle recently — I'd not trust it as ground truth on its own.

What battery chemistry are you running? The charge profile parameters that matter most vary quite a bit between LiFePO4 and lead-acid.

@Mark1978 one thing neither @ColPalmer nor @DucatoProject have mentioned yet — have you verified your battery temperature sensor is actually working correctly? If the Multiplus thinks the batteries are warmer than they are, it'll shorten absorption time considerably. Worth checking in VRM whether the temperature readings look sensible. Also, what battery chemistry are you running? If you're on lithium with a BMS that's feeding data via VE.Can or VE.Direct, sometimes the BMS signals "charge complete" prematurely and the Multiplus obediently drops to float. Had almost identical behaviour on my system last autumn before I realised the BMS charge voltage setpoint was slightly mismatched with what I'd configured in VEConfigure.

Adding to what @DerekYoung76 said about temp — worth double-checking your battery capacity setting in VEConfig too. If it's set lower than your actual bank size, the tail current calculation goes wonky and it'll think it's done way earlier than it is.

Had this exact thing with my garden office setup last year. Fogstar Drift cells, had the capacity set to 100Ah when the bank was actually 200Ah. Multiplus was jumping to float constantly. Bumped the figure to match reality and it sorted itself out overnight.

It's one of those settings that's easy to overlook, especially if you've swapped batteries at some point and forgot to update the config.