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MicroCore Systems

IP43 is the Wrong Rating for a Marine Solar Controller

|Jonathan Edwards

Every marine solar controller I've seen fail in an exposed position failed the same way — and it's not the MPPT algorithm.

The failure mode is salt-laden air reaching the PCB through the controller's venting. IP43 — the rating on Victron's SmartSolar range — permits 1mm wire ingress at any angle. It does not exclude salt spray, condensation, or the fine aerosol that coastal air carries. At 12–24 months in a direct coastal position, that becomes a corroded PCB.

The industry has built a workaround and normalised it: an aftermarket IP65 or IP67 enclosure, cable glands for every connection, and usually a longer wiring run to put the controller somewhere sheltered. Add $30–$80 NZD and an extra hour per install. Repeat on every boat that needs a controller in an exposed position.

Here's the thing: every other piece of electronics on that vessel — the VHF radio, the GPS chartplotter, the AIS receiver — is rated IP67. Standard. The solar charge controller is the one exception, and it's the one sitting closest to the elements on many installations.

What IP43 Actually Means

IEC 60529 defines the IP (Ingress Protection) rating in two digits. The first digit is solid particle protection, the second is liquid protection.

IP43 means:

  • 4 — protected against solid objects greater than 1mm (tools, wires). Dust is not excluded.
  • 3 — protected against water sprayed at up to 60° from vertical.

That second digit is the problem. A 60° spray test does not represent a marina environment. It does not test for horizontal wind-driven spray, for fine salt aerosol, or for the condensation cycle that occurs every morning when temperature drops. IP43 was designed for an indoor or sheltered outdoor environment. Not a dock.

IP67, by contrast, means:

  • 6 — dust-tight. No solid particle ingress.
  • 7 — immersion to 1m for 30 minutes. No liquid ingress.

Every piece of electronics on that vessel that is rated for exposed mounting is IP67. The standard exists. The precedent is there. The solar controller is the exception.

The Workaround the Industry Has Normalised

Ask any marine electrician who installs solar regularly and they will describe the same process: buy the Victron SmartSolar, buy an aftermarket IP65 or IP67 enclosure, add cable glands for each cable entry, run a longer wire run if needed to get the controller into a sheltered position.

It works. It adds time, cost, and complexity to every install. It means an extra box on the vessel or dock that needs to be opened every time the charge profile needs adjusting. It means the controller is not actually mounted where the wiring wants to go — it's mounted where the enclosure can live.

Three independent sources (Victron Community ×2, DIY Solar Forum ×1) document this workaround. One user noted directly: "I found the IP43 rating surprisingly low — I'm used to at least IP65 for marine equipment."

They are right to be surprised. IP43 is an indoor rating being used in a marine environment, and the marine solar industry has accepted this as normal.

The Design Implication

The correct specification for a marine solar controller is IP67, end-to-end. Not just the enclosure — the connectors and cable entry must be rated to the same standard. NorComp's guidance on marine electronics explicitly notes that connectors and cable assemblies must meet the required IP rating — a controller body rated IP67 with standard PG gland cable entries is not IP67.

This is the design constraint that defines the MicroCore Solar Charger:

  • IP67 enclosure with sealed M12 connectors on every external cable entry
  • Fanless construction — a fan housing requires a vent, and a vent is an ingress path
  • Gore ePTFE pressure-equalisation vent to manage internal condensation without creating an ingress path for salt aerosol

If a controller can't be mounted in the same position as the chartplotter, it isn't a marine controller. It's an indoor controller being used outdoors.

MicroCore Systems is building an IP67-sealed, fanless MPPT solar controller for marine and dock installations. Follow the build on Hackaday.io or reach out directly: jonathan@microcoresystems.co.nz