How to Run Inverter Appliances From Lithium
How to run AC appliances from marine lithium: size the inverter for surge, check DC current against the BMS, sequence loads, and work out realistic runtimes.
Two different specifications decide whether an appliance will run: the inverter's ability to supply the load, and the bank's ability to supply the inverter. A bank can be large enough in kilowatt-hours and still shut down, because the limit that trips is BMS current.
How do I size an inverter for my boat?
Size the inverter on three figures: the largest continuous load, the total of loads that can run simultaneously, and the surge that motor-driven appliances demand at start-up. The surge figure usually sets the rating, because compressors and pumps draw several times their running current for a moment. Then convert the inverter's continuous rating to DC current at your system voltage and check the result against the bank's continuous BMS rating. The inverter size calculator does both steps.
How do I check my BMS can supply the inverter?
Divide the inverter's maximum continuous AC output by its efficiency, then by the nominal system voltage, and compare that DC current against the battery's continuous BMS current rating. If the inverter can draw more than the BMS will pass, the BMS will disconnect under load — with everything on the bank going dark at the same moment. This mismatch is the most common cause of an apparently well-sized system failing. BMS current rating and marine lithium BMS current sizing cover it.
How do I work out how long an appliance will run?
Multiply the appliance's power in watts by the hours you want it to run, divide by inverter efficiency, and compare the result against the bank's usable energy in watt-hours. Both figures must be in the same units, which means converting the bank from amp-hours first. Remember the inverter's own idle consumption, which runs whenever it is switched on regardless of load. The battery runtime calculator combines the two.
How do I run induction cooking from a lithium bank?
Run induction cooking by sizing for a short, very high draw rather than a long moderate one: the energy per meal can be modest while the instantaneous DC current is extreme. Check the DC current at your system voltage against both the inverter rating and the BMS continuous rating, and check the conductor between bank and inverter. This load is the usual reason a boat moves from 12V to 24V or 48V. Induction cooking and electric galley lithium battery system work it through.
How do I set up air conditioning on a lithium system?
Set it up as a system decision rather than an appliance purchase: air conditioning runs for hours, so it affects bank size, charging capacity and usually system voltage at once. Work out the compressor's running watts and its start-up surge, the hours you intend to run it overnight, and the energy that implies. Then check whether your generation can replace that energy the following day. Air conditioning on lithium and air conditioning lithium battery setup cover both halves.
How do I sequence loads so I do not trip the BMS?
Stagger the start of large loads so their surges do not coincide, and where possible avoid running the highest-current appliances simultaneously. Starting a watermaker while the kettle is on can produce a combined draw that neither appliance would cause alone. Some inverters and system controllers can shed or delay loads automatically; on a simple system it is a habit rather than a feature. BMS shutdown and safe boat design covers designing so a disconnect is survivable.
How do I run a watermaker from batteries?
Run a watermaker from batteries by matching production to generation: an energy-recovery unit run during peak solar hours is a very different proposition from a high-pressure pump run at night. Work out litres per kilowatt-hour for the specific unit, then decide when in the day it should run. Watermakers also draw a substantial start-up surge. Watermaker power covers the figures to ask a supplier for.
How do I power Starlink and onboard electronics efficiently?
Power always-on electronics from DC where a DC input exists, rather than through the inverter, so the inverter can be switched off overnight and its idle draw avoided. Continuous small loads dominate a cruising boat's daily energy far more than their nameplate watts suggest, because they run for twenty-four hours. Measure them over a full day rather than estimating. Starlink and lithium batteries and laptops, phones and TV cover the usual fit.
How do I reduce inverter idle consumption?
Switch the inverter off when nothing needs it, use its power-save or search mode if the connected loads tolerate that, and move any load with a DC option off the inverter entirely. Idle consumption is small per hour and large per week, which is exactly the shape of load that a shunt reveals and an estimate misses. On boats that leave the inverter on continuously it is often among the top few consumers.
How do I run a washing machine on a boat?
Run it by sizing for the heating element, not the motor, if the machine heats its own water — that element is usually the dominant load and the reason a washing machine seems out of reach. A machine fed with hot water, or run on a cold cycle, is a far smaller proposition. Check the spin cycle's surge against the inverter as well. Washing machine on a boat covers the options.
How do I size for a windlass or bow thruster?
Size these for very high current over a very short time, and treat them as a conductor and BMS problem rather than an energy problem. A windlass may draw hundreds of amps while the anchor comes up and use very little total energy doing so. The cable run to the bow is long, which makes voltage drop the deciding calculation. Windlass and bow thruster covers both.
How do I choose between an inverter and an inverter-charger?
Choose an inverter-charger when the boat takes shore power regularly, because combining the two functions saves space, simplifies the AC distribution and allows transfer switching and pass-through in one unit. Choose a standalone inverter when shore power is rare and a separate charger is either unnecessary or better matched independently. Inverter chargers and best marine inverter charger compare the approaches.
How do I stop my inverter shutting down under load?
Diagnose in order: check whether it is the inverter's own low-voltage cut-out, the BMS disconnecting on overcurrent, or a fuse or breaker opening — each has a different fix. Voltage drop in the battery-to-inverter conductor can trigger a low-voltage shutdown while the bank itself is still well charged, which points at cable size rather than capacity. Inverter shutdown works through the diagnosis.