Victron 200ah lithium showing 14.4v at "full" but only lasting half the day — BMS issue?

Had exactly this with my shepherd's hut setup last summer — turned out the Victron wasn't actually talking to the BMS properly, so it was hitting absorption voltage but the BMS was quietly throttling current before the cells were genuinely full. 🔋

Check your VE.Bus or VE.Direct connection if you've got a Victron BMS in the loop — mine was dropping the DVCC signal intermittently and the charger had absolutely no idea.

A few things worth ruling out:

• Cell imbalance — one rogue cell hitting high voltage early, BMS calls it "full," other cells are still half-asleep
• Tail current settings — if absorption ends too early (common default settings are rubbish for lithium), you're never actually topping off
• Temperature compensation — winter in the UK means cold batteries charge slower and less completely than you'd think

Fogstar drift cells are notorious for needing a proper balance cycle if they've been sitting — had to run mine through three full cycles before capacity settled down properly.

What's your actual tail current set to in the Victron, and are you monitoring individual cell voltages? That's the real story — 14.4v at the terminals tells you almost nothing without knowing whether all cells are playing nicely together.

Reckon half the "BMS issue" threads on here are actually just dodgy charge parameters — what does everyone else think?

FellFrank | 847 posts | ⚡ Off-Grid Enthusiast

@BatteryJason classic symptom of the charger and BMS not being on speaking terms! Worth checking whether you've got DVCC enabled in VictronConnect — that's often the missing piece. When it's disabled, the Cerbo (or MPPT, whatever you're using) just chases voltage targets blindly without actually knowing the battery's real state of charge.

Also worth pulling up the BMS logs if your unit supports it. You might find the cells are actually quite imbalanced underneath, which would explain the early cutoff — one weak cell dragging the whole pack down well before the others are spent.

What BMS are you running alongside the Victron kit? Some third-party units need a specific VE.Can or VE.Direct cable to communicate properly rather than just relying on voltage alone.

Nothing says "I'm definitely living off-grid" like your battery lying to your face about being full — mine did the same in the static caravan until I spotted the Victron DVCC settings were completely wrong and the BMS was basically doing damage limitation in silence. 🔋

Check your DVCC is actually enabled in VictronConnect and that the BMS is properly controlling charge current via the VE.Bus — if it's not, you're just hitting a voltage target with no idea what's actually going in.

FETFan | 1,203 posts | 🔋 Van/Boat/Hut Tinkerer

@BatteryJason the BMS throttling current mid-absorption is the silent killer nobody talks about — your Victron hits target voltage fast because the BMS choked the amps, declares victory, and wanders off feeling smug while your cells are still half-asleep. Check your Victron's absorption time logs; if it's completing in under 20 minutes you've basically charged nothing. Fogstar cells paired with a Victron SmartSolar via VE.Direct actually lets you monitor this properly — the tail current figure tells you the real story, not the voltage. Set a proper absorption tail of around 5A and watch how long it actually takes to reach that before terminating.

Hamish1980 | 412 posts | 🏡 Scottish Highlands Off-Gridder

@BatteryJason worth checking whether your Victron is set up with the correct battery profile too — if it's running a generic lithium preset rather than one matched to your actual cells, it might be calling "full" based on voltage alone rather than tail current. On my setup I had to drop the absorption voltage slightly and set a proper tail current cutoff (around 2-3% of capacity) before the charger and BMS started agreeing with each other. Also, are you monitoring via VictronConnect? The charge history graphs are brilliant for spotting whether absorption is cutting short unexpectedly. Half a day's runtime from a 200ah bank does suggest you're genuinely not getting full cycles — could be worth logging a few charge sessions before assuming it's purely a comms issue.