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

Had this exact issue with my 100/30 last spring. Turned out the absorption voltage was set correctly but the absorption time was far too short — Victron's adaptive algorithm calculates it based on the previous day's bulk time, so if you've had a few cloudy days in a row it learns the wrong pattern and starts cutting absorption short even on a sunny day.

Worth checking a few things in VictronConnect:

• Absorption time — are you on adaptive or fixed? Try switching to fixed temporarily to rule out the algorithm being the culprit
• Tail current — if this is set too high (say 4–5% of battery capacity) it'll trigger early float even when the battery isn't properly full
• Battery voltage sensing — are you using the MPPT's built-in sensing or remote voltage sense wires direct to the battery? Cable voltage drop will fool the controller into thinking absorption is complete

My setup is a 200Ah Fogstar Drift LiFePO4 and I had the tail current set at the default which was far too aggressive for lithium. Dropping it to around 1–1.5% of capacity made a significant difference.

Also worth exporting your history data from VictronConnect and checking whether the absorbed Ah matches what you'd expect. If it's consistently low across multiple sunny days, something's definitely misconfigured rather than the battery just being genuinely full.

What battery chemistry are you running? Lead-acid and lithium behave quite differently here and the default Victron profiles aren't always brilliant out of the box for either. Would help narrow it down if you can share your current charge settings from the app.

BarryBennett | Posts: 847 | Location: North Yorkshire

@Taffy29 — worth also checking your battery temperature. The 100/30 will shorten absorption time if it thinks the battery is warmer than it actually is, especially if you've got the temperature compensation set incorrectly or no temp sensor fitted at all. Without a sensor it assumes 25°C, which in a cold battery shed in spring could be well off.

Also double-check your battery capacity setting in VictronConnect — if it's set lower than your actual bank size, the adaptive algorithm will calculate a shorter absorption period than your batteries genuinely need. Simple thing to overlook but catches plenty of folk out. What size bank are you running?