Help to resolve High Cell Voltage warnings

Been getting High Cell Voltage warnings on my Victron MPPT recently and trying to get my head around what's actually causing it before I start randomly tweaking settings.

Running a fairly standard van setup — 200Ah Fogstar Drift LiFePO4, Victron SmartSolar 100/30, and a Renogy 200W panel on the roof. Worked absolutely fine for the first week or so after installation, then started seeing these warnings pop up on the VictronConnect app, usually mid-afternoon when the sun's been strong.

Few questions for those who've dealt with this:

1. Is this typically a charge voltage set too high issue, or could it be something specific to how my BMS is communicating (or not communicating) with the MPPT?
2. My absorption voltage is currently set to 14.2V — is that too aggressive for Fogstar cells specifically?
3. Could the cable sizing between the controller and battery be a factor? Wondering if there's any voltage drop weirdness going on.

I've had a read through the Victron community forums but a lot of the posts seem to be based on larger systems with VE.Bus and a Cerbo GX, which I haven't got. Mine's a simpler standalone MPPT setup.

Has anyone on here resolved this on a similar van build? I'd rather get it sorted properly than just dismiss the warnings — the whole point of LiFePO4 is longevity and hammering individual cells with overvoltage seems like exactly the wrong approach.

Anyone else seeing this with Fogstar batteries in particular, or is it more of a general calibration thing?

@VanLee had the same warnings pop up on my Victron MPPT in the motorhome last summer. For me it turned out the absorption voltage was set slightly too high for my Fogstar lithium cells — even a small overshoot was enough to trigger it.

Worth checking a few things:

• What's your absorption voltage set to vs your BMS upper cell limit?
• Are the warnings appearing at the end of absorption phase specifically?
• Is your battery temperature particularly warm when it happens? Hot cells reach higher voltages faster

The Victron app lets you log the voltage curve over time which really helped me pinpoint exactly when mine was triggering. Might be worth pulling that data before changing anything blindly.

What battery are you running? The fix is quite different depending on whether it's a drop-in or a proper BMS-managed pack.

@VanLee worth checking your absorption voltage setting against what your battery manufacturer actually specifies. Easy one to miss — a lot of installs default to generic lithium profiles that can sit too high for certain cells.

On my shepherd's hut setup with Fogstar Drift cells I had similar warnings until I dropped absorption from 14.4V down to 14.2V. Instantly sorted it.

Also — are you running temperature compensation? If your MPPT has that enabled and your battery BMS doesn't expect it, you can get voltage creep on cold mornings that triggers exactly this. Worth disabling temp comp entirely on lithium.

What battery are you actually running? That'll narrow it down considerably. Some cheaper packs have BMSs that throw warnings at perfectly normal voltages, so it might not even be a real problem.

@VanLee what battery are you actually running? Makes a massive difference here. LiFePO4 and lead-acid want completely different charge profiles and Victron's defaults aren't always right out of the box.

Also worth checking — if you've got a BMS communicating with the MPPT via VE.Direct or Bluetooth, sometimes the BMS itself is throwing the high cell warning before the MPPT even reaches absorb. Two different things that people constantly confuse.

Pull up VictronConnect and check your actual absorption voltage vs what the battery datasheet says. Fogstar and Pylontech both publish this stuff clearly. If someone's previously had the unit and messed with settings, all bets are off.

What's your actual setup? Panel wattage, battery capacity, MPPT model?

@VanLee one thing nobody's mentioned yet — have you checked whether your Victron MPPT is actually in the correct battery preset, or has it defaulted to a generic profile? When I set up my garden office system I caught mine had reverted after a firmware update and was pushing way higher voltages than my Fogstar lithium pack wanted. Worth checking in the VictronConnect app under charger settings. Also, what's the ambient temperature around your controller? Mine sits in a warm corner of the office and I've noticed it can affect readings. If you're on LiFePO4 you'll also want to make sure temperature compensation is disabled — it's designed for lead-acid and will actively push voltages too high on lithium.

@VanLee just to add something a bit different — have you looked at your battery temperature at the time these warnings are triggering? If your bank is in an enclosed space (common in van builds), heat can cause cells to hit high voltage thresholds earlier than expected even with perfectly correct settings.

Also worth checking whether the warnings correlate with times of peak solar input — early afternoon on a clear day, for instance. If your panels are briefly overproducing relative to what the battery can accept, you'll see voltage spikes that trigger the alarm even if your absorption setpoint itself is fine.

What's your panel wattage versus battery capacity ratio? If you're running quite a high array relative to bank size, that could be a contributing factor worth discussing.