Victron 75/15 load cutting out at full charge

Been dealing with something very similar on my tiny house setup and it's worth getting into the weeds on this one.

The 75/15 uses load output disconnect as a charge protection mechanism when the battery hits absorption/float thresholds — this is by design, not a fault. The issue is that Victron's default LiFePO4 profile on that controller isn't always tuned correctly out of the box, particularly the re-connect voltage.

A few things worth checking:

• Are you using the VictronConnect app? Connect via Bluetooth dongle or the built-in BT if you have the newer revision. Go into the battery settings and check your absorption voltage, float voltage, and critically the load output low voltage disconnect/reconnect settings. If reconnect is set too close to the disconnect threshold you'll get that flickering on/off behaviour.
• What BMS is in your 100Ah lithium? Some cheaper cells (I've seen this on certain Fogstar and unbranded cells) have a BMS that sends a brief voltage spike during balancing which the 75/15 misreads as a full-charge condition.
• Your panel configuration — 2 × 40W in series giving ~28V — is fine for a 12V system on that controller, but double-check you're not occasionally seeing VOC nudging toward the 75V absolute max on cold mornings.

On my setup I ended up switching the load output mode to "Always On" in VictronConnect and managing disconnect logic through the BMS directly. Bit more faff to configure but rock solid since.

Curious whether others have found the default Victron LiFePO4 profiles reliable or whether you've all been tweaking them manually?

@SaltyRanger yes this catches people out all the time. The load output on the 75/15 isn't really meant as a permanent supply — Victron designed it primarily for small controlled loads, not as your main distribution point.

What sorted it for me on the cabin setup was moving everything off the load terminals entirely and running a proper fused feed direct from the battery, then using a BatteryProtect (the 65A one is cheap enough) triggered by the MPPT's relay. Gives you proper low-voltage disconnect without the quirky charge-state behaviour.

The VictronConnect app lets you set the load output logic too — worth checking whether yours is set to "BatteryLife" mode, which is deliberately conservative. Switching to "Always on" or a custom algorithm might be all you need if your loads are modest.

What @RetiredChef71 is getting at rings completely true from my own experience. I had this exact headache when I first wired my emergency backup setup — spent a frustrated afternoon convinced something had failed.

The penny dropped when I realised the load terminal is essentially battery-state-controlled, not just a simple switched output. Once my Fogstar 100Ah hit absorption voltage, the 75/15 cut the load as designed.

My fix was running critical loads directly from the battery through a separate fuse, then using a Victron BMV-712 to monitor state of charge properly. The 75/15's load output now only handles low-priority stuff where disconnection doesn't matter.

If you genuinely need managed load switching, look at a dedicated relay triggered by the BMV — far more controllable than relying on the MPPT's built-in logic for anything important.

Good timing on this thread — I've been puzzling over something related on my motorhome build.

Quick question for @SaltyRanger and @KevLee: when the load output cuts at full charge, does it restore automatically once the battery drops below the reconnect voltage, or do you have to manually intervene?

I'm running a Victron 75/15 into a Fogstar Drift 100Ah LiFePO4 and trying to work out whether I need to:

1. Reroute my 12v loads through a proper fused busbar instead
2. Adjust the load output settings via the VictronConnect app
3. Just accept the behaviour if reconnection is automatic

Has anyone confirmed whether option 2 actually resolves it, or does changing the load output mode (streetlight vs BatteryLife etc.) just shift the problem rather than fix it?

Worth adding — if you're hitting this repeatedly, check your absorption/float voltage settings match your battery chemistry. A lot of people run the 75/15 on defaults which are tuned for flooded lead-acid, and if you're on LiFePO4 (Fogstar Drift or similar) the voltage thresholds will be completely wrong.

In my garden office setup I run a separate relay triggered from the Victron's built-in programmable relay rather than the load output itself — far more reliable for permanent loads. The load terminal was always a bodge for small stuff like LED lighting, not running actual equipment.

@BevJackson64 for a motorhome build especially, I'd look at the VE.Direct to a BMV-712 combo — gives you proper state-of-charge based switching rather than voltage-based, which is genuinely more accurate day-to-day.