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Old 08-04-2010, 08:29   #1
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Sizing an Inverter

Hi all,

I have only a few 120v appliances that I may need to run off of an inverter. Toaster, kettle, microwave and printer. They are all 1000W. Can I use a 1000W inverter, or should I go up to 1500W.

Hank
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Old 08-04-2010, 08:46   #2
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Hank, I think it's more important that your battery bank is large enough to handle the 100+ amp draw without voltage droop. My 120v toaster and microwave can each droop my bank to 11v or less, so I generally only run them when the generator is on.

As such, the inverter handles computer and other battery chargers, my printer, etc. and doesn't have to work near its capacity, hopefully will last a long time. I'd go with the 1500W if you have the budget and space. Remember that run near its max, the inverter will generate a lot of heat that needs to be dissipated or it will overheat (good ones will cut out).
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Old 08-04-2010, 08:56   #3
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Originally Posted by Troubadour52993 View Post
Hank, I think it's more important that your battery bank is large enough to handle the 100+ amp draw without voltage droop. My 120v toaster and microwave can each droop my bank to 11v or less, so I generally only run them when the generator is on.

As such, the inverter handles computer and other battery chargers, my printer, etc. and doesn't have to work near its capacity, hopefully will last a long time. I'd go with the 1500W if you have the budget and space. Remember that run near its max, the inverter will generate a lot of heat that needs to be dissipated or it will overheat (good ones will cut out).

My battery bank is 210ah @ 48v. So i'm going to go with a 48v inverter. thinking once a day use for each of my toaster/microwave/kettle @ 5min each. roughly that would be about 6amps consumed for each appliance. That doesn't seem that much, but then again I don't fully undestand "voltage droop" and its long term effects on batteries. Anybody see holes in my logic?
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Old 08-04-2010, 09:22   #4
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The AH rating is for a low amperage draw, I think 20A. Battery capacity is inversely exponential with current draw. Trying to power a high wattage appliance is more like a CCA rating; unfortuantely, the deep-cycle batteries we use for battery banks on boats don't have CCA published.
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Old 08-04-2010, 09:35   #5
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Inverters only supply their rated output at a given temperature, when it is warmer their output goes down. My Victron loses 10% capacity going from 25 celsius to 40c, so your 1000W probably only gives you 900W in the summer. I'd go with the bigger model. 1000W is only 20A @ 48W and is well within what your batteries can supply!
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Old 08-04-2010, 09:47   #6
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ONLY 20 amps...

Quote:
Originally Posted by Zanshin View Post
I 1000W is only 20A @ 48W and is well within what your batteries can supply!
....sounds like something my wife would say.

Go with 1500 watts as a minimum. It's better for the inverter not to have to work at full capacity.
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Old 08-04-2010, 10:33   #7
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Thats's kinda the way i was leaning. Although hoping to save a couple hundred dollars and a little space.

Can anybody recommend a good 48v inverter. found this one:

Samlex 1500W, 48V, Heavy Duty Samlex Inverter - 1000 to 1999 Watts @ AltE

anybody have any experience?

hank
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Old 08-04-2010, 11:58   #8
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Victron does 48V: Phoenix Inverter 12 / 24 / 48 Volt / Phoenix Inverter Compact 12 / 24 Volt - Victron Energy

cheers,
Nick.
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