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

Had this exact issue last winter with my Multiplus II. Kept dropping to float when the batteries were nowhere near full — SOC sitting at maybe 70-75% according to the BMV-712 but the Multiplus had already given up on bulk/absorption.

Turned out my absorption voltage was set slightly too low in VE.Configure, so the charger was hitting it too quickly and deciding it was done. Bumping it up a couple of tenths of a volt sorted it completely.

Few things worth checking:

• Battery temp — if you've got a temp sensor fitted, a cold battery will cause the Multiplus to back off earlier than you'd expect
• Absorption time settings — are you on adaptive or fixed? Adaptive can be a bit aggressive with shorter charge cycles if it's learned bad habits
• Tail current threshold — might be set too high, so it's exiting absorption before the battery's properly full

What batteries are you running? Makes a big difference. My Fogstar Drift LiFePO4s needed a proper profile tweak before the Multiplus played nicely with them — the default lead-acid settings were well off.

Also worth grabbing the VRM logs if you're connected — you can see exactly what the charger was "thinking" at each stage, which makes diagnosing this a lot less guesswork.

What does your current charge profile look like?

@BorderOffGrid had almost identical with my boat setup last year. Turned out my absorption voltage was set a touch too low — Multiplus was thinking it had hit the target when it hadn't really.

Worth checking your charge current tail setting in VictronConnect. If the tail current threshold is too high relative to your bank size, it'll exit absorption early and drop to float prematurely.

Also — are you running AGM or lithium? My Fogstar Drift cells needed a completely different absorption profile to what Victron ships as default. Took me three attempts tweaking via VEConfigure before it behaved properly.

The BMV-712 SOC and the Multiplus can sometimes disagree if your battery capacity settings aren't perfectly matched across both devices too. Sync those up first — it's the easiest win.

@BorderOffGrid worth checking your charge current threshold setting in VEConfigure — it's the % of bulk current at which it decides absorption is "done" and drops to float. Default is 2% but if you've got a large battery bank that's sometimes too aggressive.

Mine was doing similar with my cabin setup (Fogstar Drift 200Ah lithiums). Bumped the tail current threshold up slightly and it sorted it straight away.

Also — is your BMV-712 set as the DVCC master? If the Multiplus and BMV aren't talking properly via VE.Direct, they can contradict each other and cause weird behaviour like this.

VEConfigure is your friend here, just don't go changing voltages randomly without noting your original settings first.

@BorderOffGrid also worth double-checking your battery temperature sensor is actually reading correctly — mine was plastered to the wrong cell and the Multiplus was basically thinking the pack was roasting when it wasn't, so it bailed out of absorption early like a nervous accountant on a rollercoaster. 🎢 Victron's adaptive charging algorithm gets very twitchy when temps are off, and in a cold van/cabin winter setup that sensor placement really matters.

Got this exact problem sorted on my garden office setup last year. Worth checking your tail current setting in VEConfigure — if it's set too high relative to your battery capacity, the Multiplus thinks absorption is done when it really isn't.

Also, are you using a Fogstar or other lithium bank? If so, make sure your absorption time isn't cutting things short either. There's a minimum absorption time setting that overrides the tail current logic — had mine set to 1hr which was nowhere near enough for my bank size.

@SaltyMaker is on the right track with the bulk current threshold — the two settings interact with each other so it's worth looking at both together in VEConfigure rather than tweaking one at a time.

Great shout from @MarkAllen69 and @SaltyMaker on the tail current — just to add a slightly different angle, have you checked whether your absorption time is set to a fixed duration rather than adaptive? If it's fixed and set too short, the Multiplus will bail out to float regardless of what the BMV is reading, since the charger doesn't actually "see" the BMV data unless you've got DVCC properly configured via Venus OS or a Cerbo. The two devices can be completely disaggregated otherwise. Worth opening VEConfigure and checking the absorption time settings alongside the tail current threshold. Also, what battery chemistry are you running? Lithium with a BMS asserting a charge complete signal could explain this too.