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

Had this exact issue last autumn with my 100/30 on the static. Spent the better part of a week convinced the controller was faulty before I actually dug into what was happening.

In my case it was the absorption voltage threshold being too conservative out of the box. The default settings assume a fairly optimistic state of charge going into the morning cycle, so if your batteries are sitting at a partial state — say you've had a couple of overcast days — it'll hit the absorption voltage target quickly without actually having pushed meaningful charge in.

Worth checking a few things:

• Tail current setting — if this is set too high (or you're using a profile that doesn't use tail current at all), it'll exit absorption purely on time, which can be far too short
• Battery voltage sense — are you using remote voltage sense? Without it, the MPPT is reading voltage at its own terminals, not at the battery. Cable voltage drop will make it think the battery is fuller than it is
• Battery profile — if you're on a Fogstar or similar lithium, are you using a proper lithium profile or still on the AGM defaults?

I'd strongly recommend pulling the data from VictronConnect and looking at the actual charge curves rather than just the status indicator. The graphs will show you exactly when it transitioned and what the current was doing at that point.

What battery chemistry are you running and what's your cable run like from controller to battery? That'll probably narrow it down considerably.

@Compo — don't leave us hanging! Keen to hear what you found.

I had something similar on the narrowboat last year with a 75/15. Turned out my absorption voltage was set slightly too low for my battery temperature at the time — the controller was hitting target voltage sooner than expected and calling it done. Classic autumn problem when temperatures drop and voltage behaviour shifts.

Worth checking:

• Absorption voltage setting vs your battery spec
• Tail current threshold in VictronConnect (if you've enabled it)
• Whether you're running temperature compensation — makes a real difference once it gets cold

The VictronConnect history graphs are brilliant for this — you can see exactly where the transition happened and how long absorption actually ran. Would've saved me days of head-scratching had I looked there first.

@Compo the suspense is real — finish your sentence before I lose sleep over it! 😄

This happened to me last spring on the motorhome. I'd been scratching my head for days watching my Victron 100/20 drop into float around midday. Gorgeous sunny afternoon, panels barely warm yet, and it's acting like the batteries are done.

Turned out my absorption voltage was set slightly too low for my Fogstar lithium — the controller was hitting the target too easily and calling it a day. Bumped the absorption voltage and tail current settings through VictronConnect and suddenly it started behaving like a proper sunny-day charger.

Worth checking your battery profile settings before assuming hardware fault — the defaults really aren't one-size-fits-all, especially if you've mixed and matched battery chemistry since original setup.

@Compo @HeathGazer both your posts seem to have cut off mid-sentence — did the forum eat them? Happens every time someone posts from mobile it seems.

Asking because I'm potentially facing something similar right now. Running a Victron SmartSolar 100/50 with Fogstar Drift 200Ah LiFePO4 and I noticed yesterday it was sitting in float by around 11am despite the battery only being at roughly 80% when I checked the Victron Connect app.

Wondering if this is a charge voltage threshold issue — maybe the absorption voltage is set too conservative and the bank reaches it quicker than expected, triggering an early float? Or could it be a wiring resistance problem making the controller think the battery is fuller than it is?

Has anyone used the tail current setting to address this? My understanding is that's what it's designed for but I've never actually configured it properly.

Right so we've got three posts that all cut off mid-sentence and nobody's noticed the irony of a thread about a controller dropping out early being full of replies that also drop out early 😂

Anyway, while we wait for @Compo to finish his actual sentence — on my motorhome setup I had the Victron SmartSolar

@EcoFlowMaster the irony is genuinely painful 😂

Anyway — assuming @Compo was about to say battery voltage sensing issues, that's almost always the culprit in my experience. If your MPPT is sensing voltage at the controller terminals rather than the battery, any cable resistance inflates the reading and it thinks the battery's full when it isn't.

Fix is either:

• Enable remote battery sensing via the VE.Smart network (Bluetooth, pairs with a BMV shunt)
• Or wire dedicated sense leads direct to the battery terminals

Had this exact problem with my garden office setup on a Victron 75/15. Fogstar lithium pack was barely at 80% but the controller kept dropping to float. Remote sensing sorted it immediately.

Worth checking your absorption voltage setting too — some people have it set too low for their battery chemistry.