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

Had this exact issue last summer with my 100/20. Drove me mad for weeks.

Turned out my battery voltage sensing was the culprit — I had quite a long cable run between the MPPT and the battery bank, so there was enough voltage drop to fool the controller into thinking the batteries were fuller than they actually were. Once I added remote battery voltage sensing (proper sense wires direct to the terminals), it sorted itself out almost immediately.

Worth checking a few things:

• Absorption voltage set correctly for your battery chemistry? Fogstar Drift cells want different settings to a AGM
• Absorption time — in VictronConnect you can set a minimum absorption time so it doesn't bail out early
• Tail current setting — if this is too high it'll drop to float before the batteries are properly topped off
• Temperature compensation — if you've got a temp sensor attached, a warm battery reads artificially "full"

What battery type are you running? And are you connecting via VictronConnect to watch the charge curve in real time? That live graph is genuinely useful for diagnosing where it's cutting short — you can see exactly what voltage it's hitting and when.

Mine's a lithium setup in a tiny house so I'm pretty fussy about getting the charge profile dialled in. Took a bit of fiddling but it's been rock solid since.

Anyone else found the default tail current setting way too generous out of the box?

WayneClark | 📍 Yorkshire | ⚡ 400Ah LiFePO4 | ☀️ 780W

@PanelMatt — classic voltage drop issue that one! Worth mentioning for anyone else reading: you can actually enable the remote battery sense feature on the Victron app and connect the sense wires directly to the battery terminals. Makes a massive difference when you've got longer cable runs.

Also worth checking your absorption time settings in VictronConnect — if you're on the default "adaptive" mode, it calculates absorption time based on the previous day's discharge, so a fairly full battery coming into the morning will cut to float quite quickly. Might not actually be a fault at all depending on your setup. What battery chemistry are you running? AGM and lithium behave quite differently in this regard.

Ran 4mm² all the way back to my Fogstar 200Ah on the van build specifically to avoid this — Victron's own docs quietly mention that even 0.1V of cable drop can fool the MPPT into thinking absorption is done early, which is basically the controller gaslighting itself with bad data.

If remote battery sensing isn't wired in, you're just flying blind on voltage. The Ve.Direct Bluetooth dongle will show you exactly what the MPPT thinks the battery voltage is versus reality — sometimes that delta is embarrassingly large.

LiFePO4Nerd | 📍 Array | ⚡ Off-grid & Motorhome | ☀️ Victron devotee

@PanelMatt this catches people out constantly. The bit nobody mentions: LiFePO4 makes it worse than lead-acid because the absorption window is so narrow — your MPPT barely gets a sniff of that voltage plateau before it decides "job done, float time."

Worth enabling BatteryLife off entirely if you're running lithium, and double-checking your battery profile isn't still set to a lead-acid template. I've seen Victron units shipped with AGM defaults and owners wondering why their Fogstar cells are being babied at 14.1V absorption.

Also — have you tried wiring the VE.Smart network with a BMV-712 for remote battery sensing? Transformed my setup. The MPPT then reacts to actual battery voltage rather than guessing through cable resistance.

Enable remote battery voltage sensing in VictronConnect and your MPPT basically stops guessing — mine went from tantrum mode to textbook charge curves overnight.