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Old 08-18-2016, 03:35 PM   #1
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1000 Watt Inverter

Hello, Folks! What's the difference between a lawyer and a catfish? Well, one's a low-life, scum sucking, bottom dweller . . . the other one's a fish! Biddie Bang Biddie Boom! Yes, I am a lawyer, but somedays I'd rather be a fish. Now for my question: I am looking at a 1000 Watt Inverter from Harbor Freight that connects to a 12V battery to give me a little bit of power while on the beach at Padre Island National Seashore, which has no hookups. The inverter information does not state how big of a battery is needed to produce 1000 watts of power, nor does it state how long the battery/inverter power will last when using it conservatively. I intend to use it mostly to power electric fans and my electronics. I will use it to power the refrigerator and/or microwave as needed. I appreciate any and all advice from the senior experts on this forum. I'm still learning how to turn on the light switch.
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Old 08-18-2016, 04:00 PM   #2
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1000 watts won't power a microwave. The Harbor Freight invertors are not pure sine wave invertors and should not be used with many electronic devices. 1000 watts will most likely not handle a refrigerator (depending on size). If you want to run fans, small electric drills or other smaller wattage devices that are not power sensitive then the Harbor freight modified 1000 watt invertor will do the job.
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Old 08-18-2016, 05:23 PM   #3
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Most "cheapee" inverters are not only modified sine, but are also rated at "Peak" and not continuous. A 1000 watt inverter will most likely reliably produce about 800 watts without tripping off if the peak (starting up a small drill for example) lasts more than a few seconds.

So at 800 Watts, any 12 volt battery will need to supply about (800/12) or 67 amps. A single fully charged 75AH Dual Purpose Marine battery will not be able to sustain 12 volts for very long at that size of a power draw.

Using the graph below as a guide (instead of 100 AH think 100% of 5 amp rated capacity for 20 hours - the definition of Amp Hour), a 75AH @ 5 amps (60 watts) will last 15 hours (or 100% of its rated capacity).

At 12.5 amps (150 watts), the capacity to deliver power will drop to 70% of rated capacity or 10.5 hours.

The chart does not go to 67 amps, but at 44 amps (525 watts), the capacity of the battery to deliver 12 volts will die (drop to 10.5 volts) at 45% of rated time or about 6.75 hours.

With only one deep discharge battery, buying anything more than a 500 watt inverter is a waste of money and that single battery will only last 6 or 7 hours before it is deader than Elvis.

So, forget the microwave and coffee maker; think more like a small TV or laptop computer and a phone charger or two for maybe 2 - 3 days before recharging.

For example, my HP laptop's transformer draws 120 watts continuous.
A small LCD TV draws between 85 and 125 watts depending on model.

Yea, I know ... bummer, right?
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Old 08-23-2016, 09:00 AM   #4
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What about while driving with 2 deep cycle batteries? Will engine maintain charge for 2 bateries?
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Old 08-23-2016, 09:52 AM   #5
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I installed a 1500 watt unit in my Ole Toyhouse years ago. Mainly to run the microwave and also make morning coffee.

We didn't have a genny, and only had a standard Group 27 Walmart marine battery, so we couldn't run the high loads to long, maybe 15 minutes or so. (We'd run the truck to recharge the coach battery)

My 1500 watt would not run the 5000 BTU AC unit. It would run the blower, but couldn't start the compressor, the inverter would kick out with an overload error.

An interesting side effect of RVs, a lot of people learn about energy conservation, and get an awakening on how much it costs to generate electricity.

Here's a link to my old Toyhouse inverter install..

http://toyotamotorhome.org/forums/in...erter-install/

..
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Old 08-23-2016, 10:13 AM   #6
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Quote:
Originally Posted by msubryan View Post
What about while driving with 2 deep cycle batteries? Will engine maintain charge for 2 bateries?
An automobile alternator will easily maintain the charge on even 4 deep cycle batteries. What it won't do is recharge even one deep cycle battery in any reasonable amount of time.

The reasons are complex and involve the difference in construction between a deep cycle and a starting battery, the voltage regulator and design of the alternator, and the distance (and wire gauge) between the trailer battery and the alternator.

https://answers.yahoo.com/question/i...9124749AAoihZL

Here is a great article on using an alternator to charge deep cycle batteries (attached).
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File Type: pdf Automobile Alternators as Chargers.pdf (805.9 KB, 19 views)
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