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Old 09-29-2016, 08:55 AM   #121
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CMS: thanks for that post. I've got to read it a few more times as there's a lot of great information in it.
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Old 09-29-2016, 10:06 AM   #122
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Originally Posted by tcpip95 View Post
- Thank you for catching the cable size issue. I'll be going with 2 AWG and will keep the length less than 5'.


"Go with 5000 at 80% duty cycle". Not sure I'm following you there. What does the 5000 represent?

I have been looking at this one: AIMS Power PICOGLF30W12V120VR 3000 Watt 12V Pure Sine Inverter Charger


- 3000 Watt continuous pure sine power
- 9000 Watt peak power for 20 seconds
- Built in 100A smart battery charger with 7 selectable battery type settings
- Auto gen start feature
- Marine and industrial grade


I will be purchasing the window A/C unit and doing the test that twistedtree is suggesting.

Please keep the feedback coming. It is greatly appreciated.
Wire Size - Check the manual for that Inverter - it recommends 4/0 for the 3KW unit <3M cable run

Consider 5000 - I think the poster was recommending considering a smaller A/C unit (5000 BTU) recognizing that it will run longer
This might be worth considering as the max Amps will be lower - A/C smaller cheaper$? - inverter req'd smaller - cable size lower - starting Amps lower - overall a cheaper system - it will just run longer but I don't see where that would be a problem

- Am I missing something???

Might be worth working up a second scenario
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Old 09-29-2016, 10:25 AM   #123
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Don't overdo this. You don't need an underground bunker with a bank of submarine batteries, state of the art inverters, first rate engineered cabling and control systems, engineered battery management protocols, etc, etc.

You just need to run a cheap chinese window AC unit for a few hours to cool down a bedroom.

My vote is for the smallest AC possible, it will be fine for one room with a towel shoved under the door. A 2kW inv and four golf cart batts should do it.

It's not like you are designing a system for a trawler where you are going to have in use for months at a time. If things are so bad you don't get power back in a week, you probably will run out of gennie gas. And stations will be out too.
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Old 09-29-2016, 10:35 AM   #124
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OK, here are some answers and background:


The statement "5,000 at 80%" was derived from your specification of installing a 10,000 BTU A/C and running it at 40% duty cycle. I and others suggest that a smaller 5,000 BTU unit would work better as it will run at a longer duty cycle and keep the room comfortable at a lower humidity and higher temperature. Unless the bedroom you are cooling is huge, 5,000 BTU should work fine and keep the humidity lower and use less energy than the 10,000 BTU unit. It might get warm during the middle of the day, but you won't be sleeping there then and since you can run your generator until 10:00 PM that should give plenty of time to cool down so the A/C reaches its set point and starts cycling.


AIMs Inverter/Charger- These haven't developed a reputation in the boating market or the home solar panel market. I suspect AIMs is Chinese and all that that implies.


A quality 2,000 watt inverter and 100 amp charger won't be cheap, something near $2,000. Several brands that have a good reputation in the boating market are Magnum and Victron and MasterVolt. I have mixed feelings about MSW inverters. Usually they do fine running motors like the A/C. A sine wave inverter is more expensive and usually less efficient.


I was a little surprised by one poster's criticism of cheap AGMs for deep cycle service. I had thought that all AGMs were basically the same and worked fine in deep cycle service. But he sure sounded like he knew what he was talking about.


What I do know is that golf cart batteries will work well in your application and are 1/3 the cost of the better AGMs he mentioned. You might have to add water twice a year with these and in your garage off gassing isn't an issue.


You won't know your amp hour consumption at night until you try it and see what the system really does. I think you will be in the 300-400 AH range. I hadn't considered the effect drawing down the battery bank at more than 1/20 the capacity per hour and that will certainly bring them down faster and you don't want to go below 50%. I would start with 880 AHs of capacity (8 GCs) and add more if necessary. BTW, they are about $85 each for Duracell GCs at Sam's, but I would check with battery supply shops since you are making a big purchase. You might even get Trojans for near that price- worth 10% more IMO than Duracells.


I do understand Ski's point above that all you need is a simple system. It doesn't need to withstand the rigors of full time cruising. A small A/C powered by the AIMS inverter and supplied by 6 GC batteries should work, even if the batteries are taken down to 30% by morning. You can always add a couple of more batteries if testing indicate that is happening.


You are in Florida, right? Forget about a swamp cooler.


David
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Old 09-29-2016, 10:35 AM   #125
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"a cheap chinese window AC"?

Bill Kimley's (of Seahorse Marine located in China) idea of a cheap Chinese AC system is a damp towel draped over you with a fan overhead.

Funny thing is it actually works.

.
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Old 09-29-2016, 01:15 PM   #126
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Thanks again for all the input.

Ski's idea makes sense. I'm adjusting my overall plan. I'll use a different room (guest bedroom) which will be 205 sq ft of space to cool. That will easily allow me to downsize the window A/C unit to 5,000 btu. That will have the ripple effect (power-wise) that you all have mentioned. In addition, this room faces due east, so the hot afternoon western sun will not heat this room up as much.

Some real-world numbers on the 5k btu Frigidaire model I'm looking at, from someone who used an inline power meter for measurements:
fan only low: 57w
fan only high: 60w
low cool w/compressor: 324w
high cool w/compressor: 336w
start-up peak: 400w

Running these numbers through OC's formula, and substituting in 80% duty cycle, I come away with 211 ah continuous draw for 8 hours (assuming 85% efficiency of inverter).

I would up the battery capacity to 450 ah. Someone mentioned the Trojan line of batteries. Trojan has an office right here in Ft. Myers. They only wholesale to dealers, but they referred me to a golf cart vendor here in town who's an authorized dealer. I can get 4 of the Trojan T-105 6v 225ah batteries new, out the door, for $485. That would get me 450ah @ 12v DC.

So now I've got the A/C, and batteries. The only other thiing I would need is the inverter/charger.

Based on the changes we're making, I think the Go Power! GPC-75-MAX 100 Amp 4-Stage Converter/Battery Charger should be sufficient, no?
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Old 09-29-2016, 02:10 PM   #127
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That Go Power model is not an inverter. Also didn't I remember that the no generator times are between 10:00 PM and 7:00 AM. That is a minimum of 9 hours and may be 10 if you sleep in a bit.


Try your system out one night once you get it set up. The next morning, turn the power to the inverter/charger off and let the batteries rest for at least 4 hours then measure the specific gravity and compare against this Trojan chart. You need to stay above 50%.


http://www.trojanbattery.com/pdf/Tro...UsersGuide.pdf


Then plug it in for 14 hours to recharge. Unplug it and let sit until morning. Check the specific gravity against Trojan's chart. Add batteries if you are much below 95%.


Or you can hook up a battery monitor for another $200 and closely monitor the state of charge dynamically.


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Old 09-29-2016, 02:34 PM   #128
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David, thanks for catching that about it not being an inverter. I need to pay closer attention to what's actually written LOL.

The times for no generators are 10:00 pm - 6:00 am, so it will be 8 hours on batteries.
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Old 09-29-2016, 02:52 PM   #129
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Thanks again for all the input.

Ski's idea makes sense. I'm adjusting my overall plan. I'll use a different room (guest bedroom) which will be 205 sq ft of space to cool. That will easily allow me to downsize the window A/C unit to 5,000 btu. That will have the ripple effect (power-wise) that you all have mentioned. In addition, this room faces due east, so the hot afternoon western sun will not heat this room up as much.

Some real-world numbers on the 5k btu Frigidaire model I'm looking at, from someone who used an inline power meter for measurements:
fan only low: 57w
fan only high: 60w
low cool w/compressor: 324w
high cool w/compressor: 336w
start-up peak: 400w
A watt meter can't be used to determine in-rush loads as it is far to slow.. The in-rush can be many times more than running and in general at least double to triple running load. The HF 1800 can handle 3600W for about 0.3 seconds so an 1800W HF inverter is cutting it close.

I just measured the 5k BTU Haier air conditioner in my daughters bedroom using my Fluke 376 (current and in-rush) & Fluke 289 (voltage).

AC Service Voltage = 119.22V
Running High AC = 4.1A (Ran 5 min before taking measurement)
In-Rush/Start Up 26.4A
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Old 09-29-2016, 03:24 PM   #130
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Startup inrush on various machines is all over the map. Unless you can find data for the machine at hand, you pretty much just have to try it. Some older machines the compressors were very easy to start, and some newer ones would stomp on what seemed to be an adequately sized inverter or generator.

You never know til you try it or test it.

Inrush also changes depending on what kind of power source you are using.
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Old 09-29-2016, 05:23 PM   #131
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In-Rush/Start Up 26.4A
The math says that thing pulled 3,168 watts.

Not doubting you for a minute, but HOLY COW! Never would have expected that. That Xantrex is cutting it close.

Hmmm.....
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Old 09-29-2016, 05:47 PM   #132
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I don't like running anything close to the edge. CMS just gave me some real world numbers, and as Ski points out inrush numbers can be all over the place - maybe even higher that what CMS just measured.

The AIMS Power PICOGLF20W12V120VR 2000W Pure Sine Inverter Charger looks - at least on paper - to beat the pants off of the Xantrex HF 1800.

The cost difference between the Xantrex HF 1800 and the AIMS is about $100 ($473 vs $588 for the AIMS), but the AIMS will give me a wider margin of error on load (6,000w for up to 20 seconds).

One point of concern on the AIMS is that this model is not UL Listed. They have a version that is UL Listed, but it's another $100. I need to check and see if local code dictates UL-Listed or not.
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Old 09-29-2016, 05:55 PM   #133
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Go buy the 5,000 btu window shaker; install it in the guest bedroom window, and buy a power consumption meter. The meter is good for up to 15 amps and will show you how many watts you consumed over night. Then do a test run by sleeping in the room with the central AC turned off and the window unit plugged into the power consumption meter plugged into the wall outlet. No more guessing; you will know how much stored energy you will need. Between the AC unit and the meter, you will probably invest less than $300 in the experiment.

Ted
I posted this in the other thread. Why don't you start with this and get real consumption numbers. You could even try it in both bedrooms as a comparison. Once you have solid KW consumption numbers for a whole night, you can be much more precise about the other parts.

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Old 09-29-2016, 06:41 PM   #134
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I posted this in the other thread. Why don't you start with this and get real consumption numbers. You could even try it in both bedrooms as a comparison. Once you have solid KW consumption numbers for a whole night, you can be much more precise about the other parts.

Ted
Thanks Ted. That is my plan. I was not aware of the "inrush factor"; that's significant enough to warrant the larger inverter by itself. The rest of it I will "back into" as I get real world numbers from the actual A/C unit.
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Old 09-29-2016, 09:52 PM   #135
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I think I'd just go to a hotel for a few days.
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Old 09-29-2016, 10:15 PM   #136
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I think I'd just go to a hotel for a few days.
Where's the fun in that?

Actually, if after a week we're still in trouble, we've probably got bigger problems. Truck will be full of diesel just in case we need to bug out.
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Old 09-29-2016, 11:43 PM   #137
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Sleep in the truck with AC on. 1gal in two or three hours. Cheaper than batteries and inverters and hotels.
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Old 09-30-2016, 06:20 AM   #138
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"Sleep in the truck with AC on. 1gal in two or three hours. Cheaper than batteries and inverters and hotels."

Except in most states ideling long term is illegal, and if caught could be expensive.
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Old 09-30-2016, 03:13 PM   #139
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Quote:
Originally Posted by CMS View Post
A watt meter can't be used to determine in-rush loads as it is far to slow.. The in-rush can be many times more than running and in general at least double to triple running load. The HF 1800 can handle 3600W for about 0.3 seconds so an 1800W HF inverter is cutting it close.

I just measured the 5k BTU Haier air conditioner in my daughters bedroom using my Fluke 376 (current and in-rush) & Fluke 289 (voltage).

AC Service Voltage = 119.22V
Running High AC = 4.1A (Ran 5 min before taking measurement)
In-Rush/Start Up 26.4A
Would a "soft start" device be helpful in this case?
Something like one of these from Hyper
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Old 09-30-2016, 04:34 PM   #140
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Would a "soft start" device be helpful in this case?
Something like one of these from Hyper
Likely cheaper to get a more powerful inverter?
If you got to buy one anyway.
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