Does pre-setting the battery voltage let us skip wire connection order?

Been scaling up a small solar lighting build using Victron SmartSolar MPPT 75/15 controllers and this question's been nagging at me before I roll out another batch.

Standard wisdom says: battery first, then panels — always. But if you've already pre-configured the battery voltage in the VictronConnect app before the unit even sees a live connection, does that change anything? My gut says no, the connection order still matters for protecting the MOSFET circuitry, regardless of what the firmware thinks it's looking at. The controller still needs to detect and confirm battery voltage on startup before it should ever see panel input.

Tried skipping the order once by accident on a 12V LiFePO4 setup (Fogstar cells, naturally) and the controller threw a fit — not catastrophically, but enough to make me paranoid about doing it at scale.

That said, I've seen people in various threads swear blind that pre-setting via Bluetooth sorts everything. Feels like someone's going to brick something expensive and learn the hard way.

For those of you deploying multiple units — are you strictly enforcing battery-first on every install, or has pre-configuration given you any wiggle room in practice? Keen to hear if anyone's actually stress-tested this properly rather than just going by feel.

Would be especially useful from anyone who's done larger rollouts — solar street lighting, shed installs, that sort of thing — where connection discipline across multiple systems gets a bit messy in the field.

@DaleLover oh this rabbit hole caught me out on my shepherd's hut build last spring!

Short answer: no, pre-setting voltage doesn't skip the connection order. The controller still needs to sense the battery physically connected first before it does anything sensible — the stored setting is just a starting preference, not a substitute for proper initialisation.

Think of it like telling your car the destination before the engine's running. The 75/15 specifically will throw a fit (or worse, silently misconfigure) if it detects panels before battery on first power-up.

Stick to the sequence religiously:

1. Battery
2. PV panels

Every. Single. Time.

I learned this the hard way when I rushed a garden office install and fried a fuse doing it backwards. Victron's own documentation is pretty unambiguous on this — it's not just folk wisdom.

@DaleLover to add some technical weight to what @VivaroNomad is getting at —

The pre-set voltage is stored in firmware/memory, not actively output on the terminals. The moment you connect battery-first, the controller samples whatever's actually on those terminals to establish its reference. Pre-setting changes nothing about that sequence.

More critically: connecting PV first creates an uncontrolled path through the MOSFET body diodes. On a 75/15 that's survivable once, maybe. Do it repeatedly and you're degrading components quietly.

The connection order isn't about voltage matching — it's about inrush protection and safe reference establishment. Victron's manual is unambiguous on this: battery → PV, reverse for disconnect.

I've got three 75/15s running my shepherds hut and EV charge sequencing. Never deviated from that order. Not once.

@DaleLover done this exact thing on my narrowboat build, curiosity got the better of me once. Spoiler: the controller still saw 0V on the battery terminals first, firmware profile made no difference whatsoever.

The preset is just a charging target — it doesn't change what the hardware senses at the point of connection. That initial voltage spike when you connect battery last is a physical event, not a software one.

Stick to battery → solar every single time. On the 75/15 specifically there's not much headroom to absorb a badly timed transient before something gets unhappy.

Victron's own install docs are pretty unambiguous on the order too, worth keeping a screenshot for when clients or mates try to argue the toss.

@DaleLover worth adding one practical angle nobody's mentioned — even if the firmware did somehow handle it perfectly, you'd still be voiding the warranty by deviating from the connection sequence Victron explicitly documents. Their support team will ask about it if you ever raise a claim.

On my tiny house build I use a sticky label on each controller reminding me: battery → solar → load. Takes seconds and becomes muscle memory after the first few installs. When you're rolling out a batch it's easy to get complacent and cut corners that look harmless on paper.

Stick to the sequence. Pre-configured profiles are about convenience during commissioning, not about bypassing hardware protection fundamentals.