Power and electrics
Eight instincts watch the part of the van that everything else depends on. One of them, cold-charging protection, is the only instinct that acts rather than simply telling you.
Cold-charging protection
Charging a lithium battery below freezing damages it permanently, and it happens quietly, in minutes. This instinct watches for charge current going into a pack while any of that pack's temperature probes reads below your threshold. Both have to hold for two minutes, so a single odd reading does not trip it.
It is the only instinct that acts rather than simply telling you. With Charge cut-off on, Sensa switches off every charge source it can control: the MultiPlus inverter mode is stepped down so the charger stops without changing anything else you had running, each Cerbo MPPT solar charger is switched off, and a DC-DC charger wired through a power relay is turned off at the relay. Sensa remembers how it found them, so once every pack has climbed 3°C past your threshold and held there for ten minutes, it puts them back exactly as they were. If you changed one of them yourself in the meantime, your choice wins and Sensa leaves it alone.
Settings: Alert below 2°C, range -5 to 10. Charge cut-off, on by default.
Default: Alert.
You need: a battery reporting both temperature and current, such as a Roamer Gen 1 or Gen 2, or a Fogstar pack. An Orion DC-DC charger cannot be switched by software, so unless it is wired through a relay it is covered by the alarm only.
Shore power dropped
You are hooked up, and the site bollard or its breaker trips overnight. Without this you find out at breakfast, with a flat battery. Sensa watches the incoming supply and speaks up when it fails while you were connected.
Where it can, Sensa uses the AC input voltage, because that is independent of load: it sits near 230V while the bollard is live and collapses when it trips. Where there is no voltage reading it falls back to the shore power figure, which is less dependable because the wattage legitimately idles near zero on a full battery with no AC loads.
Driving away is the one honest way shore power disappears, so when Sensa can see engine RPM it holds the alarm back while the engine is definitely running.
A charger that has switched itself off is not a lost supply. A MultiPlus that finishes charging overnight and then switches off stops measuring its own input and reports zero volts, which on that reading alone is indistinguishable from a tripped bollard. Sensa now checks the unit's own state first and stays quiet when it is simply off. On a van with two inverters each is paired to its own unit, so one being off never silences the other. If the state cannot be read at all, the alarm goes ahead: not being able to check is not the same as being told all is well.
Restarting your system no longer sets this off either. A restart used to leave the watch primed, so the first proper reading afterwards, zero volts on a van that had never been hooked up, was mistaken for the supply failing.
Settings: For 5 min, range 1 to 60.
Default: Alert.
You need: a shore power sensor, typically a MultiPlus-II reporting through a Cerbo GX.
Engine Start
This one works differently from the rest. Rather than watching a level, it triggers on an event, the engine starting, and then runs a list of departure checks. Today there is one check, shore power still connected, and more will be added to the same instinct over time. Each check has its own switch and its own Warn or Alert choice, so you can keep some and drop others.
Turn the key with the lead still plugged in and you will know about it before you have moved.
Settings: each check carries its own enable and its own Warn or Alert choice.
Default: Warn, and deliberately a quiet one. It writes to the Log without raising a pop-up. Switch the check to Alert if you want it to insist.
You need: an engine RPM sensor and a shore power sensor.
Low leisure battery
A straightforward level watch on the leisure battery's state of charge, so you get a heads-up while there is still time to do something about it.
Settings: Warn below 20%, range 5 to 50.
Default: Warn.
You need: a battery state-of-charge sensor, such as a Victron SmartShunt, a battery reading through a Cerbo GX, or any of the supported wireless battery packs.
Starter battery watch
Everyone watches the leisure battery, and almost nobody watches the one that actually starts the engine. This watches the starter voltage and speaks up if it sags and stays there for ten minutes. A cranking dip lasts seconds, so it will not trip on that.
There is deliberately no check for whether the engine is running. The alternator holds around 14V while you drive, so the condition clears itself, and a sustained sag with the engine running means a failing alternator, which is worth knowing about just as much.
Settings: Warn below 11.9V, range 10.5 to 26, in steps of 0.1. The top of that range is there so a 24V vehicle can set a sensible figure of around 23.8V.
Default: Alert.
You need: ideally a SmartShunt with its auxiliary sense wire connected to the starter battery, because that reading is always live. A WiCAN OBD2 adapter can supply it instead, but the adapter sleeps when the vehicle is parked, which is exactly when this instinct is watching, so it is the second choice.
Battery cell imbalance
One cell drifting out of step with the rest is the earliest sign a pack is going wrong. Sensa watches the spread between cell voltages and speaks up when it stays above your threshold for ten minutes. The delay matters: the spread widens briefly under heavy load and at the top of a charge, and neither of those is a fault.
If you have more than one pack, each is watched separately.
Settings: Alert above 100mV, range 20 to 500, in steps of 10.
Default: Alert.
You need: a battery that reports individual cell voltages, such as a Roamer Gen 1 or Gen 2, or a Fogstar pack. Victron Smart Lithium does not publish a cell spread figure, so this instinct shows as Unavailable on those.
Battery output turned off
Every lithium pack has a discharging switch in its own app, and switching it off takes that pack out of the bank: it stops supplying anything, sits at full charge, and the other batteries carry the whole load. Nothing else in the van looks wrong while this is happening, because each pack on its own is perfectly healthy.
It is easier to do by accident than it sounds, and it can sit unnoticed for months. This instinct watches each pack's discharging switch and speaks up when one has been off for five minutes. The alarm names the battery, and the fix is in that battery's own app rather than anywhere in Sensa.
A pack that has dropped off Bluetooth is not reported as switched off. Sensa waits until it can actually read the switch again.
Settings: none.
Default: Alert.
You need: a battery that reports its discharge switch, such as a Roamer Gen 1 or Gen 2, or a Fogstar pack.
Batteries out of balance
The catch-all for the same problem arriving some other way. A blown fuse, a loose lug, an isolator left off or a pack quietly failing all end the same way: one battery doing far less of the work than the others, and nothing obviously broken.
Sensa compares the state of charge across your packs and speaks up when the gap between the highest and the lowest stays above your threshold for two hours. Two hours is deliberate. A bank does genuinely converge on its own after a full charge, and a newly fitted pack starts life out of step with its neighbours, so this is a "something is wired or switched wrong" alert rather than an urgent one.
It compares charge rather than voltage on purpose. Batteries wired in parallel are joined at the busbar, so every pack that is actually working reads the same voltage whatever its charge, and the one that has dropped out is the only one that differs. Charge is the reading that shows the gap.
Packs that have gone quiet are left out of the comparison, and at least two have to be reporting before a gap can be claimed at all. On a van with a single battery there is nothing to compare, so the instinct never appears.
Settings: Alert above 25%, range 5 to 60, in steps of 5.
Default: Alert.
You need: two or more batteries reporting their state of charge.