Document the MPPT 75|10 LOAD turn on process

Been meaning to write this up properly for ages after digging into this on my shepherd's hut build last winter.

From what I've observed with my Victron MPPT 75|10, the load output turn-on sequence isn't instantaneous — there's a definite staged process happening. Once the battery climbs back above the re-connect voltage threshold (set via VictronConnect, dependent on your chosen algorithm — I use BattLife on my 100Ah Fogstar Drift LiFePO4), the MPPT doesn't just slam the load on.

What I think is happening:

1. Battery voltage meets or exceeds the re-connect threshold
2. The MPPT briefly asserts a low voltage (~1V-ish) across the load terminals — almost like a pre-check or soft-assert
3. There's a short dwell period before full voltage is switched through

I've seen this cause confusion with some 12V devices that interpret that low-voltage pulse as a legitimate supply and attempt to boot, then reset when full voltage arrives. Had exactly this with a cheap Chinese relay module in my hut's lighting circuit — drove me absolutely mad for a week.

Questions for the thread:

• Has anyone actually scoped the load terminals during this transition? I'd love to see a proper waveform capture rather than relying on multimeter snapshots
• Does the pre-assert voltage or dwell time change depending on which load algorithm is selected?
• Any difference in behaviour between firmware versions? I'm on fairly recent firmware but haven't compared

Worth documenting this properly because Victron's own literature is surprisingly vague on the mechanics of it. Would be genuinely useful for anyone designing load circuits that need clean, reliable switching.

@BatteryBarry good thread, been curious about this myself for the shepherds hut setup.

Few questions before I chip in properly:

• Are you running the load output directly, or via a BMS controlled relay?
• What battery chemistry are you seeing this on — LiFePO4 or lead-acid? I'd expect the turn-on threshold behaviour to differ quite a bit
• Is the sequence you're documenting specific to the VE.Direct connected mode or standalone?

From my own narrowboat testing with a 75|15 (close enough), I noticed the load output has a slight delay after the battery voltage recovers past the reconnect threshold — maybe 2-3 seconds. Wondered if that's consistent with what you're seeing or if the 10 behaves differently.

Also worth checking whether VictronConnect logs show anything useful at the moment of turn-on — the alarm log sometimes catches voltage dips around that transition.

@BatteryBarry this matches almost exactly what I saw during my van build when I first wired the 75|10 into my Fogstar 100Ah LiFePO4.

Worth noting — the load output does a quick voltage check before it'll even consider switching on. If your battery is sitting below the "load disconnect" threshold you've set in VictronConnect, it simply refuses, no drama, no clicking. Caught me completely off guard the first time because I assumed it had failed.

The bit that tripped me up specifically was after a deep discharge overnight — even once solar started pushing charge back in, the load terminal stayed dead until the battery climbed back above the "load reconnect" voltage. Not the same figure as disconnect. Took me embarrassingly long to realise those are two separate parameters buried in the settings.

Ran mine through a logic analyser last summer out of sheer motorhome-related boredom — the load output does a brief voltage sense before switching the MOSFET, which is why you sometimes see a tiny blip on a multimeter before full turn-on. Worth noting the streetlight/load algorithm setting in VictronConnect completely changes this behaviour, so if yours isn't matching @BatteryBarry's sequence, check you're both on the same load output algorithm (Algorithm 0 vs the timed options). Caught me out for an embarrassing amount of time.

Good write-up @BatteryBarry. One thing worth adding from my static caravan setup: the 75|10's load output behaviour changes noticeably depending on whether you've configured it via VictronConnect as BatteryLife or a fixed voltage algorithm. With BatteryLife enabled, the reconnect threshold is adaptive — it shifts upward dynamically based on recent discharge history, so you can't simply assume a fixed re-enable voltage. Caught me out badly first winter when the load wasn't coming back on at the voltage I expected.

Also worth noting: if you're running a Fogstar or similar lithium with a BMS that can disconnect under load, the 75|10 can misinterpret the resulting voltage spike as a "battery full" condition during the turn-on sequence. Seen it trigger a false absorption phase in my setup. Decoupling your load from the BMS output where possible avoids that particular headache.