Sunday, January 21, 2024

Inverter "Power Boost" Feature

 Many modern inverters have a "power boost" feature that is super useful.  I'm really talking about combined inverter/chargers, but I'm just going to call them inverters for simplicity.  When you are plugged into shore power, or running a generator, that power source is limited, typically to 30A or 50A.  If you overload it, a breaker trips.  To keep this from happening, it's your job to manage the power loads on the boat to keep them under the limit of the power source.  This typically means limiting how may appliances are turned on at once, not heating water while cooking dinner, etc.  Doing this isn't the end of the world, but it's kind of a pain.

For some time now, inverters have been able to help with this by varying how much they are charging the batteries.  In addition to all your boat loads, the inverter itself is an additional load when it's charging your batteries, and can consume close to, if not all of the available incoming power.  These smarter inverters have a setting where you can tell them what the incoming power limit is, and they will only use for charging whatever capacity is left over after powering the other loads.  So if your shore power is 50A, and your boat loads are consuming 30A, the charger will consume no more than 20A, ensuring that the shore power isn't overloaded, and no breakers trip.

This has been a great help to boat operators, but it has limitations.  In particular, the inverter can control how much power it consumes, but it can't control what boat loads are placed on the inverter.  So going back to our example, if the boat loads are 55A, there is nothing the inverter can do to reduce that, and you will trip a breaker.  But then along comes "power boost".

Those clever inverter engineers realized that not only could they reduce the internal charger consumption to manage the shore power load, they could actually turn the inverter back on and use it to supplement the shore power to support even larger boat loads.  So these super-smart inverters will see a boat load of 55A, and they will use the inverter to draw from the batteries to supply 5A to supplement the 50A from shore power, and now the loads work without tripping any breakers.  Then when the loads subside, the inverter goes back to charging to replenish what it took from the batteries.  Pretty cool, right?

This takes another huge bite out of power management on a boat.  You can now exceed shore power capacity by whatever your inverter capacity is.  You just need to be sure that the average consumption is less than the shore power capacity so you don't continually draw down the batteries.  This simplification to load management is so great that I depended on it in our power system design.  For example, our shore power connection is 50A, yet I know that the HVAC system can exceed this for periods of time.  But this power boost feature allows that to still work with a much more common 50A power connection vs a much less common 100A connection.  We almost never have to do load management.


  1. Thanks Peter, Good to have you back cranking out Nordhavn knowledge. We've missed that while you were commisioning/testing.

  2. I do love this feature. I also use it when at anchor. I can keep the inverter from overloading the generator which is running things not on the inverter, like the battery charger. It's a bit of a pain to reset the input limits, but it's useful and the breakers never trip.


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