Anyone else had issues with Victron MultiPlus overheating on a narrowboat in summer?

Running a Victron MultiPlus-II 24/3000 on my narrowboat and it's been cutting out intermittently over the past few weeks during the hotter afternoons. The unit's mounted in the engine bay which I know probably isn't ideal, but space is genuinely tight. Ambient temps in there have been hitting around 40–45°C on sunny days according to my cheap sensor.

The MultiPlus is set to its default temperature protection settings — I haven't touched any of the thermal thresholds in VictronConnect. It trips out, the fan runs for a bit, then it comes back maybe 10–15 minutes later. Load at the time is usually only around 1.5–2kW, so it's not like I'm hammering it.

Has anyone managed to solve this with better ventilation, or is relocation basically unavoidable? Wondering if a small 12v extraction fan ducted to pull cooler air through would actually make a meaningful difference, or whether I'm just papering over a real problem. Also curious whether lowering the charge current in VEConfigure during summer months would reduce heat generation enough to help.

@GeoffHenderson80 this is exactly my concern with my own boat setup — where specifically in the engine bay is yours mounted? I've been reading that the MultiPlus-II needs at least 10cm clearance on all sides for adequate airflow, and engine bays can easily hit 50°C+ on a warm summer afternoon even with the engine off.

A few questions that might help diagnose it:

• Is the thermal cutout showing in VictronConnect when it trips?
• Have you checked whether the temperature sensor is actually connected properly?
• What's your load typically running at when it cuts out?

I'm seriously considering relocating mine to a dedicated ventilated locker rather than the engine bay. Has anyone done this successfully on a narrowboat where space is obviously at a premium?

@GeoffHenderson80 not a narrowboat but I've had similar thermal cutout issues with a MultiPlus in my shepherd's hut during last summer's heat. The Victron manual specifies it needs decent airflow around all sides — even a few centimetres of clearance wasn't enough when ambient temps crept up.

Worth checking a few things:

• VictronConnect app will show you the actual temperature log so you can confirm it's definitely thermal rather than something else
• The unit has a built-in temperature sensor but you can also add an external one
• Derate curve kicks in around 40°C ambient — an engine bay could easily exceed that in summer

Have you considered relocating it outside the engine bay entirely? Even a small dedicated vented locker would make a big difference. What temperatures is your engine bay actually hitting?

ValleySoul | 847 posts | ⚡ Solar Enthusiast

@GeoffHenderson80 engine bays are brutal for this — ambient temps can easily hit 50°C+ in summer even without direct sun. The MultiPlus has a thermal cutout around 60°C internal, so it doesn't take much.

A few things worth trying: check the VE.Bus status in VictronConnect to confirm it's definitely thermal rather than overload. Also look at your PowerControl settings — reducing the input current limit slightly reduces heat generation during heavy charging cycles.

If you can get even a small 12V fan blowing across the heatsink fins it makes a massive difference. Some boaters run a temperature-triggered fan from a simple thermostat controller.

Longer term, relocating it to a dedicated ventilated cabinet away from the engine bay is really the proper fix. @VanJulie worth considering this for your setup too before summer peaks.