Over-Voltage

[Roaring Girl]

Hi to the electrical experts - which we most definitely are not. Thanks in advance for advice, particularly the words in simple English for confused non-techies.

We are constantly experiencing a high-voltage problem (from 14.5 to 15.6v) which shows up as problems with our 12v microwave (bleeping and showing a high voltage sign), our fridge pump (overrunning) and our alpenglow lights which are very unhappy with too much power.

To describe this very specifically - the fridge (12v, watercooled with a pump) works very much as expected when not plugged in. When we are on shore power, it kicks in as required by the thermostat, and pulls power from the battery; the charger starts pulling in shore power, which then gets dumped to the fridge which then powers its pump much harder than needed or good for the pump.

The boat was mostly rewired in 2003, and we have a 2x 220aH domestic bank of AGM batteries. We use a victron multiplus charger/inverter (installed 2007) and have both a 240v system (only used when we have shore power) that does not run through the batteries, and a 12v system for everything else. A Balmar max charger is the regulator for the alternator

When away from the shore (most of the summer) we use solar, wind and a second alternator on the engine.

The battery voltage is at 13.2 to 13.3v when not attached to shore power but fully charged. The generators are all doing their jobs nicely. The problem is with the amount of voltage hitting the actual appliances.

This may be a really stupid question, but we cannot work out how to moderate this, so the appliances are not being damaged. Everything we have tried manages either the voltage in the batteries, or the impact of limited shoreside power, not our particular problem.

This system was professionally installed (in the UK) and has been reviewed twice since then by further professionals. It's not just us!

Any thoughts on this would be very much appreciated.