Load Output Current - 100/20 SmartSolar MPPT

Been scratching my head over this one with my own setup on the shepherd's hut, so thought I'd throw it out here.

I'm running a Victron 100/20 SmartSolar MPPT and trying to nail down the actual maximum current the load output terminals will handle. The TDS is a bit vague on this — it gives you the charge current spec clearly enough (20A, obviously) but the load output rating seems to be buried or missing entirely depending on which version of the doc you're looking at.

From what I've pieced together through the Victron community forums, the load output is typically rated at 20A continuous on the 100/20, but I've seen a few people suggest it's actually a bit lower in practice — something like 15A when you factor in thermal derating. Has anyone actually tested this properly?

My concern is that I've got a small 12V compressor fridge plus some LED lighting running off the load terminals, and on a warm day in the hut it's all adding up. The VictronConnect app shows the load current peaking occasionally and I'd rather not be pushing limits I don't fully understand.

A few questions for anyone who's been down this road:

• Do you run loads directly off the MPPT load output, or do you route everything through the battery with a separate BMS/fuse arrangement?
• Is there a thermal cutout that kicks in before any damage occurs?
• Anyone had issues with the load output on the 100/20 specifically?

Would be good to hear from folk with real-world experience rather than just datasheet guessing!

@CornishBoater the load output on the 100/20 is rated at 20A continuous, but there's a catch that trips people up — it shares that 20A ceiling with the charging current.

So if your controller is pushing 15A into the battery, you've only got 5A headroom on the load output before it gets unhappy.

In practice I'd treat the load output as convenient for small 12V accessories only — lights, a control relay, maybe a water pump. For anything meaningful on a shepherd's hut (kettle, inverter, EV charging obviously) you want to pull direct from the battery through a proper fused circuit.

Also worth checking in the VictronConnect app — the load output behaviour can be configured (on/off, BatteryLife algorithm, etc.) which catches a lot of people out when their loads mysteriously cut off at dusk.

@CornishBoater worth noting that the 20A load output and the 20A charge current share the same rating — they're not additive. So if you're pulling heavy loads through that terminal while simultaneously charging, you can end up in a situation where the controller is working harder than people assume.

Personally I ditched the load output on mine fairly quickly. Ran it through a proper Victron BatteryProtect instead — far more reliable for a shepherds hut setup where you might have varied loads at odd hours. The built-in load terminal is handy for small, predictable stuff but I'd be cautious relying on it as your main switching point.

What's actually connected to yours? That would change the advice considerably.

Good point from @ExPostie there. One thing worth adding — the load output on the 100/20 is also temperature-limited in practice. If the controller gets warm (which it will in a confined hut install), it'll derate before you hit that 20A ceiling.

On my narrowboat I run a separate fused bus bar for loads rather than relying on the MPPT load output at all. Victron's own guidance suggests the load output is really suited to smaller, managed loads — think lighting circuits or a water pump — rather than running anything significant continuously.

If your shepherd's hut needs meaningful load capacity, honestly worth looking at a proper DC distribution setup rather than leaning on that output terminal. The Cerbo GX route gives you much better monitoring too if you're expanding the system.

Good additions from @YorkshireVanLifer and @ExPostie. One thing nobody's mentioned yet — the load output on the 100/20 uses a virtual load algorithm in VictronConnect, so your actual disconnect/reconnect voltage thresholds matter enormously for protecting your battery. If you're running LiFePO4 (Fogstar Drift, for instance), you'll want to set those thresholds carefully rather than leaving the defaults, which are calibrated for lead-acid.

Also worth checking: the load output current is not fused internally at 20A — Victron expect you to fit an external fuse as close to the battery as practical. Caught a few people out on here before when they've assumed the controller handles that protection itself.

For my Vivaro build I actually abandoned the load output entirely and ran everything through a separate Victron BatteryProtect, which gives you far more flexibility with higher current loads.

Really useful thread — I've been wondering about this too for my narrowboat setup.

@VivaroAdventure's point about the load output using PWM is something I hadn't considered. Does that cause any issues with sensitive electronics? I'm thinking about running a small router or LED lighting off it directly.

Also, is there any practical advantage to using the load output versus just wiring loads directly to the battery with a separate fuse? I've seen some people bypass the load output entirely and manage everything through a Cerbo GX or similar. Wondering whether the built-in low voltage disconnect on the load output is actually worth relying on, or whether a dedicated battery protect like the Victron BatteryProtect would be more robust for anything critical.