Anyone else's Victron MPPT refusing to bulk charge after a firmware update?

Woke up this morning to my SmartSolar 100/30 sat in float at 7am with 60% SOC — cheers for that, Victron.

Rolled out the update two days ago on my cabin setup (200Ah Fogstar lithium, 400W panels), and now the thing thinks "absorption done" before it's even started. Absorption voltage set to 28.4V, float at 27.2V, all looks correct in VictronConnect but it just... doesn't bulk properly anymore.

Anyone seen this after the latest firmware push, or have I somehow managed to break a charge controller by pressing update? Genuinely asking because my emergency backup is now neither charged nor particularly useful.

HalfAJob93 | 47 posts

@MultiPlusNerd Had almost identical grief with my 75/15 after an update last autumn — turned out the battery voltage sense was reading slightly high due to a dodgy BT connection during the update, so it thought it was already at float threshold. Worth checking your absorption voltage is still set correctly in the app rather than relying on a preset that might have reset itself. Mine had quietly reverted to a AGM profile somehow.

Also, what's your float voltage set to? If it's crept up close to your absorption voltage the controller can get confused and skip bulk entirely. Fogstar cells are fussy about that gap being right.

Try a full settings reset and manually re-enter everything rather than restoring from a backup profile — sometimes the backup carries the corrupted value across with it.

PYW_VanLife | 312 posts

@MultiPlusNerd Worth checking whether the update reset your battery profile back to default — mine did exactly this after a firmware push and it was sitting in float prematurely because the absorption voltage had dropped to the AGM preset rather than my lithium settings. Jump into VictronConnect, go into the battery settings and double-check your absorption and float voltages are still correct for the Fogstar. Also check your tail current setting — if it's too high it'll exit absorption early and drop to float well before the battery's actually full. Fogstar's own spec sheet lists the recommended charge parameters, worth cross-referencing. If everything looks correct and it's still misbehaving, there's a "restore default settings" option followed by manually re-entering everything that sometimes clears whatever the update scrambled.

Squib82 | 203 posts

@MultiPlusNerd One thing I haven't seen mentioned yet — check your absorption time settings. Some firmware versions have quietly reset the "adaptive absorption" algorithm, which can cause the MPPT to interpret a shallow voltage rise as absorption completion and drop straight to float, even at low SOC.

On my SmartSolar 100/50 aboard the boat, I noticed similar behaviour after a v3.14 update. The culprit was the "tail current" threshold — it had reverted to a very low value (something like 1A), so the charger was calling "done" far too early.

Go into VictronConnect → Battery settings and cross-reference every parameter against your Fogstar's spec sheet. The tail current for a 200Ah cell ought to be closer to 2–4A typically.

Worth doing a full BMS disconnect/reconnect cycle afterwards too, just to clear any cached state.

KN_Builds | 891 posts

@MultiPlusNerd Also worth checking your BMS communication if you're running the Fogstar with a VE.Direct cable to the MPPT. I've seen the SmartSolar defer to an external charge signal after certain updates, and if the BMS handshake isn't quite right it can convince the controller that the battery is already satisfied.

Try disconnecting the VE.Direct temporarily and running the MPPT in standalone mode — if it bulk charges properly without it, your issue is almost certainly in the BMS/MPPT communication layer rather than the firmware itself. Fogstar have been pretty responsive on their support email in my experience, worth dropping them a line alongside whatever Victron say.

George1972 | 47 posts

Had something similar after a SmartSolar update last year — mine ended up stuck in float because the battery voltage sense had been toggled off during the update. Worth checking in VictronConnect under the MPPT settings whether it's reading voltage accurately at the battery terminals rather than just at the controller itself.

Also, what's your float voltage set to? If it got reset to default (13.5V on mine after an update) and your resting voltage is sitting just above that, it'll never leave float regardless of SOC. Fogstar lithium wants it higher than the lead-acid defaults Victron tend to revert to.

@KN_Builds raises a good point on BMS comms too — is yours connected via VE.Direct or just standalone?

GlenDoug | 512 posts

Worth being precise here — "refusing to bulk charge" and "sitting in float at 60% SOC" aren't necessarily the same fault.

If it's genuinely skipping bulk and jumping straight to float, that's usually a history/tail current issue. Check your tail current setting in VictronConnect; if it's set too high relative to your panel output, the MPPT can mistakenly decide the battery's full.

On my garden office setup (similar SmartSolar 100/30, 206Ah Fogstar) I had the tail current default cause exactly this after a config reset.

Also — did the firmware update reset your battery preset? Worth double-checking your charge voltages against Fogstar's spec sheet. Their lithium profile is quite specific and a reset to AGM defaults would cause odd behaviour like this.

FrostySailor | 234 posts

@GlenDoug makes a fair point on terminology. That said, I've seen the SmartSolar exhibit odd behaviour post-update where it misreads the battery voltage and enters float prematurely — particularly if the absorption voltage threshold got reset to defaults.

Worth pulling up the history tab in VictronConnect and checking what absorption duration it actually logged. If it's showing near-zero minutes in absorption before float, that's your culprit — the voltage setpoints have almost certainly been wiped.

On my narrowboat setup I always export my charge profile before any firmware update precisely because of this.