C30 microwave power consumption?

[serpa4]

Is the micro a 1000 watt or what? I'd like to do the VxA=watts calculation to see the amps it pulls off batteries.

 

[Wee Venture]

If you have the Muave 0.7 cu ft microwave, it is rated at 1150 watts input power (700 watts output). So at 12VDC you are looking at 95 amps or so. (If you wanted to really get technical you could subtract a few amps for actual voltage higher than nominal 12V but then add a bit for losses in the inverter. But 95 amps is a good approximation.) So one fully charged 110 AH battery would give you approximately a half hour of run time if that were the only thing drawing power from it. I like to have my engine running if I am going to run the microwave on the inverter though we have sometimes run it for short periods of time just on the house battery bank.

John

 

[Martin610]

Let me help out here a bit.

The Muave is a 120 volt unit. If we're powering that via the inverter we are supplying it with 120 volt AC power.

Therefore I think the calculation is 1000 watts divided by 120 volts and would equal about 8.3 amps.

These paper calculations are always approximate, good for planning. Always best to use a clamp meter and read the draw directly. Not always easy to get at the wires though.

Battery run time is highly variable. The phone company is a major contributor to that issue because we use absolutely huge quantities of these in our systems. The rule of thumb where you can get 50% of the capacity of a FLA battery is based on our conditions in the central office which has controlled temperature, controlled draw, etc. I don't think you ever see 50% in the real world.

-martin

 

[serpa4]

Thanks all. I guessed 125 amps at 1500 watts out of a 1000 watt micro. Guess I was off a lot in a good way. 95 amps is a lot less.

 

[Martin610]

Some context may be helpful.

A 4 bedroom house typically has has 150 amp service. The whole house.

Most fluid motion boats have 30 amp service, some have 50. All the wiring in the boat is gauged for that amount. Higher than that breakers blow and wires melt.

That helps you figure out where upper and lower limits would have to be. Most of the appliances on the FM boats are going to be 20 amps or less. Exceptions might be the stove top and AirCon that need 25 amps.

 

[serpa4]

Finally figured how to get micro to run on the inverter. It was an inverter setting. I DO have the 1000watt with convection. On the actual victron shunt, it pulls 130 amps. The convection was less at 116 amps 12v DC.

 

[Alpina]

Some context may be helpful.

A 4 bedroom house typically has has 150 amp service. The whole house.

Most fluid motion boats have 30 amp service, some have 50. All the wiring in the boat is gauged for that amount. Higher than that breakers blow and wires melt.

That helps you figure out where upper and lower limits would have to be. Most of the appliances on the FM boats are going to be 20 amps or less. Exceptions might be the stove top and AirCon that need 25 amps.

I think a lot of confusion on the forum comes from the conversion from AC amps back to DC amps since the batteries is what supply the inverter the power. And then there are components that only work on DC. The answer depends on which portion of the circuit people are speaking about.


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[Alpina]

Finally figured how to get micro to run on the inverter. It was an inverter setting. I DO have the 1000watt with convection. On the actual victron shunt, it pulls 130 amps. The convection was less at 116 amps 12v DC.

Do you recall which setting you changed and to what? Sometimes my microwave runs for a few seconds and then quits. If I keep trying it will eventually work. I don’t use it much off shore/generator power so I haven’t the details crisp in mind. I know your details were different than mine but maybe I will learn something.


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[serpa4]

My inverter kise 2000 has 3 settings.
1 if no shore power, inverter is off after like 20 seconds.
2 if no shore, inverter goes to standby.
3 if no shore, stay on.
So I'd turn on inverter on battery, but it would turn itself off after 20 seconds. I set to if no shore, go to standby.

I was only concerned with the DC side of the equa6. Even on the inverter, I am concerned with how much it's pulled from my 12volt bank.

 

[Alpina]

Thanks serpa4.

Not sure if you've seen them but there are some great videos on youtube put out by FM called "As the prop turns."

Here's one on power management, if you haven't seen it: https://www.youtube.com/watch?v=Uj_am-ecSt4&t=2934s

They reference a spreadsheet in there which is helpful. You input the how long you plan on using specific devices and it sums up the total amp-hours consumed.

Here the link: https://www.dropbox.com/sh/x39enzb027so ... lator.xlsx

Plugging into the spreadsheet: 1150W running for 15 minutes will consume 24 Amp.Hr. If you have 4 batteries totaling 440AmpHr, you have effective capacity of 220AmpHr with standard batteries when new. Under the above conditions, using the microwave for 15 minutes would consume ~11% of your battery capacity not accounting for solar panel charging.

Franco

 

[serpa4]

Microwave, 1000 watts, pulls 130 DC amps according to the Victron BMV gauge.

 

[Wee Venture]

Microwave, 1000 watts, pulls 130 DC amps according to the Victron BMV gauge.

That seems about right. Microwaves are normally rated by output power (sometimes referred to as “cooking power”). The input power is greater because of inefficiencies. Our 700 watt Mauve actually has an input power of 1150 watts. If we use that same ratio, a 1000 watt microwave would actually draw about 1,643 watts. At 12.5VDC that works out to about 131 amps from the battery bank, which is almost exactly what you measured.

John