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Old 08-15-2013, 01:05 PM   #1
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Default Inverter to run a 500-700 watt microwave

What would it take to run a 500-700 watt microwave? I am looking for what inverter would work and then how much battery juice. Thanks,
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Old 08-15-2013, 05:01 PM   #2
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run it for how long? I'm sure there is a formula somewhere...pie r square..nah.....dang. Do you want it to run the microwave for say like 5 minutes? then drain the batteries or have a lot to spare? I used to have a houseboat with 110v fridge, microwave, coffemaker, lights , stereo etc. I had a 2500 watt inverter and 6 big deep cycles. Batteries would last fair amount of time but micro and coffeemaker would put a good drain on them if I remember correctly. I'm sure there are some experts that will come along shortly
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Old 08-15-2013, 05:14 PM   #3
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Most of the good inverters have a good start up capacity. I think I would look for at least a 1250 or so.

It will handle the startup plus still operate some small stuff onboard. ( we are not talking costco)
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Old 08-16-2013, 02:26 AM   #4
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I have a Freedom inverter 1500 watt on my Fortier and a 1000w compact micro. I use the micro only occasionally to heat up coffee and the like and don't see any noticeable impact on the batteries (1 house 1 starter). Never have used it for long periods when off shore power though.
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Old 08-16-2013, 07:19 AM   #5
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Originally Posted by JAGSARE1 View Post
What would it take to run a 500-700 watt microwave? I am looking for what inverter would work and then how much battery juice. Thanks,
Rough estimates for battery juice-
700w @ 120Vac = 6amp +/- (watt/voltage). To get amps at 12vdc, multiply by 10 = 60amps per hour.

10min of micro use = 10 amp +/-, 20min = 20amp+/-. Plus whatever loss occurs at the inverter.

(Deep Cell)
Group 27 battery holds 100 amp hours +/- = 1 hour of mirowave useage at best - with battery in perfect condition at full charge.

4D battery = 200 amp hours.

(non deep cell starting battery)
A standard starting battery - one with high cold cranking amps but low continous output may last 20-30 min max.
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Old 08-16-2013, 08:27 AM   #6
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Read this, and this.
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Old 08-16-2013, 08:39 AM   #7
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Originally Posted by JAGSARE1 View Post
What would it take to run a 500-700 watt microwave? I am looking for what inverter would work and then how much battery juice. Thanks,
500-700 watts

Sorry, had to make a joke.
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Old 08-28-2013, 02:12 PM   #8
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I'm sorry, I completely forgot about this thread. Still not sure which direction to go. I was simply looking at a small microwave in the console of my boat to heat a sandwich or something. The engines will be running when this happens. Using Jughed's info above, I should be able to use a microwave pretty easily with 2 deep cycle batteries for short uses especially with the engines running at the same time right?
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Old 08-28-2013, 02:19 PM   #9
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Originally Posted by JAGSARE1 View Post
I'm sorry, I completely forgot about this thread. Still not sure which direction to go. I was simply looking at a small microwave in the console of my boat to heat a sandwich or something. The engines will be running when this happens. Using Jughed's info above, I should be able to use a microwave pretty easily with 2 deep cycle batteries for short uses especially with the engines running at the same time right?
Did you read my links?

Jughed's information is correct.

Last edited by river_boater; 08-28-2013 at 04:19 PM. Reason: correction
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Old 08-28-2013, 03:51 PM   #10
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Go to a Rv type store .
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Old 08-28-2013, 04:03 PM   #11
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Did you read my links?

Jughed's information is incorrect.
Ummm, care to explain how?
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Old 08-28-2013, 04:04 PM   #12
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Wrap the sandwiches in foil and heat them by putting them on top of the running engine.
Lasagna would be fine but not fried chicken.
Seriously it works.
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Old 08-28-2013, 04:19 PM   #13
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Ummm, care to explain how?
I just looked at your calculations again, and you are correct--AC appliances draw 10 times their rated amps when running on 12 volts. Brain fart.
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Old 08-28-2013, 04:37 PM   #14
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I just looked at your calculations again, and you are correct--AC appliances draw 10 times their rated amps when running on 12 volts. Brain fart.
No prob... And I was double checking against what your link says, they match up - except the author made a mistake that confuses the issue. He equated running the motor starter to operating a coffe pot. He was off by a big factor. The motor starter may pull 10-20x the current of the coffee pot.

If the OP has two group #27's in parrallel, he has 180-200 stored amp hours, microwave and inverter uses about 1.25 amps per min. 6-8% of the battery capacity for a 10 min run.
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Old 08-28-2013, 06:50 PM   #15
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Did you read my links?

Jughed's information is correct.
Yes I did. Thanks. Jughed's info just took it 1 step farther.
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Old 08-28-2013, 06:51 PM   #16
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Originally Posted by reel axin View Post
Wrap the sandwiches in foil and heat them by putting them on top of the running engine.
Lasagna would be fine but not fried chicken.
Seriously it works.
Not real smart running around in the ocean with the cowling off the outboard just to heat a sandwich. Inboard, yes, outboard, not taking the cowling off for anything.
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Old 08-28-2013, 06:52 PM   #17
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Quote:
Originally Posted by Jughed View Post
No prob... And I was double checking against what your link says, they match up - except the author made a mistake that confuses the issue. He equated running the motor starter to operating a coffe pot. He was off by a big factor. The motor starter may pull 10-20x the current of the coffee pot.

If the OP has two group #27's in parrallel, he has 180-200 stored amp hours, microwave and inverter uses about 1.25 amps per min. 6-8% of the battery capacity for a 10 min run.
I am still unclear on the size of the inverter though?
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Old 08-28-2013, 10:44 PM   #18
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I am still unclear on the size of the inverter though?
You will add things later. So if you need 700 watts output now you must increase for the loss in conversion and start up. A 1000 will operate your 700 microwave but a 1250 would be the way I would go.
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