Battery power for home during power outage

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.

tcpip95 said:

- 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.

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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

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.

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

"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.

.

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?

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/TrojanBattery_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.


David

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.

tcpip95 said:

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

Click to expand...

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

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.

CMS said:

In-Rush/Start Up 26.4A

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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.....

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.

O C Diver said:

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

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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

O C Diver said:

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

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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.

I think I'd just go to a hotel for a few days.

Capt.Bill11 said:

I think I'd just go to a hotel for a few days.

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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.

Sleep in the truck with AC on. 1gal in two or three hours. Cheaper than batteries and inverters and hotels.

"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.

CMS said:

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

Click to expand...

Would a "soft start" device be helpful in this case?
Something like one of these from Hyper

Bacchus said:

Would a "soft start" device be helpful in this case?
Something like one of these from Hyper

Click to expand...

Likely cheaper to get a more powerful inverter?
If you got to buy one anyway.

I'm going to go with that AIMS 2,000w model. 6,000w start for 20 seconds should give me what I need. Just need to determine if I neel UL Listed for code compliance.

tcpip95 said:

I'm going to go with that AIMS 2,000w model. 6,000w start for 20 seconds should give me what I need. Just need to determine if I neel UL Listed for code compliance.

Click to expand...

I have watched a lot of reviews and he is thorough, Samlex is one of the best.
Aims he does not recommend them.

Threads combined into OFF TOPIC forum.

I'm not surprised at the 3000+ watt starting load on a 5K btu air conditioner. That is what it took to start the 5K AC on my boat.

If you look at the label on the compressor you'll see LRA followed by numbers. LRA is locked rotor amps. Unless the AC is equipped with some sort of start helper, this is pretty close to what it takes to start the thing.

I solved the problem on my boat by installing a Sepco Hard Start Capacitor. They are less than twenty bucks. It allowed me to start and run my boat AC on a Honda 1000. Come to think of it I put on on my 8k wall unit at home and ran it on a Honda 2000.

I'm running off at the fingertips so you might want to pour a cuppa coffee!

Ski in NC said:

We too tend to shelter in place, even if that means some risk. Mostly because the gov't knuckleheads prevent returning in a timely fashion. "It's not safe..." Oh pleeeaasse... They don't realize that by sticking to a "zero risk" policy regarding and thus delaying return, they are encouraging folks to take large risks by staying put.

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Exactly.

tcpip95 said:

Bringing it back to what I was originally asking about...

I'm looking at the following:

KEY ASSUMPTIONS
1. window A/C will be 10k btu Frigidaire; consumes about 7.7 amps.
2. over an 8 hour period that will be about 565 ah w/12v battery bank.
3. I'm expecting to be able to run at about a 40% duty cycle, which would work out to be about 226 ah.
4. I factor in a margin of 50%

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Today I tested (Killawatt meter) on the neighbor's Frigidaire 12k btu a/c unit. His starts at 120 watts and moves up to 1180 watts when cooling. Like mine his starts with just the fan then a minute later the cooling part kicks in.

Figure 1% for fan, and 10% for the cooling part when doing your math. Though the "real" math works at 7.7 amps I'd use 10 as a figure. You're going to have line-losses and there's your safety margin of error...

djmarchand said:

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.

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I have had and use an AIMS1000 (square wave) on Seaweed since 2010. It works fine. No issues.

It even will power my a/c unit. Mine is the simple dial Haier, not the one with a digital and remote. It works though. My Haier 5k btu will work from my batts using the AIMS1000.

CMS said:

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

Click to expand...

I see different figures for certain. When my Haier starts (on 3.5 incidentally of 10) first the fan starts. That 45 watts. Then a minute later the cooling part kicked in. The AIMS1000 handled it. I did not see anyplace near 26A draw. It went to 455 and then climbed up to 485.

HopCar said:

I solved the problem on my boat by installing a Sepco Hard Start Capacitor. They are less than twenty bucks. It allowed me to start and run my boat AC on a Honda 1000. Come to think of it I put on on my 8k wall unit at home and ran it on a Honda 2000.

Click to expand...

The other "trick" is to have your a/c turned on when you start the genny. During start-up (for the generator) you get more than peak amps out. That brief time-span when it's putting out extra can sometimes get larger power draws started.

Anyway, that's my take.
I did upgrade to an pure sine wave AIMS1200 recently. The AIMS1000 would not power my microwave. It's a newer one with digital controls. Though the nuker came on and the turntable moved it didn't sound right and nothing heated.

Pure sine wave solved that issue.
Hey, a girl's got to have popcorn with her afternoon DVDs.

J, who almost has this decadence thing down to a science.

Good luck. I did want to share that AIMS works for me. I did burn up the first AIMS1000 after 55 weeks at anchor. I came into a dock and the first thing I did was plug in -- without unplugging the inverter. Smoke. Toasted that thing.

The AIMS1200 has a cord and automatically disconnects when a/c power is present. It automatically will restart too when the a/c goes out. It's a hefty unit. The good thing for me is that the inverter can be mounted in any direction. And it comes with a remote control so I can shut if off when starting Betsy (my engine)

The AIMS 1200 does not have a charger. I prefer separate units.

Walmart sells Group 27's that are 109A for $80 each. That's what I have in Seaweed and they are fine. I check them on the first of each month.

janice142 said:

I see different figures for certain. When my Haier starts (on 3.5 incidentally of 10) first the fan starts. That 45 watts. Then a minute later the cooling part kicked in. The AIMS1000 handled it. I did not see anyplace near 26A draw. It went to 455 and then climbed up to 485.

Click to expand...

Without the proper measurement tools designed to capture in-rush you won't see it. A kilowatt meter won't capture in-rush. Your inverter likely have better in-rush specs than the Xantrex previously discussed which could only do double its rating for 0.3 seconds.

janice142 said:

I did burn up the first AIMS1000 after 55 weeks at anchor. I came into a dock and the first thing I did was plug in -- without unplugging the inverter. Smoke. Toasted that thing.

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This is an unsafe and dangerous installation, if that is what happened..

BandB said:

I thought I'd toss a bit of Fort Lauderdale requirements on installations of generators.

EMERGENCY GENERATORS
Requirements for Permitting and Installation
(OPTIONAL STANDBY FOR RESIDENTIAL USE)
Emergency generators must be submitted as a package with the following items:
1. Electrical Permit Application.
2. Two (2) copies of the Electrical Riser Diagram showing entire service, including:
a. transfer switch.
b. all conduit and wire sizes.
c. overcurrent protection of generator and equipment.
3. Two (2) copies of the Generator Specifications (usually supplied by the manufacturer).
Specifications must provide length, width and height of the generator to be used.
4. Two (2) copies of Site Plan (survey) highlighting the location of the generator:
a. showing exact location of proposed generator (minimum 5’ from building openings).
Exhaust must be minimum 10’ from building openings.
b. showing exact location of fuel tank (if applicable).
c. providing the dimensions of the distances between the proposed generator/fuel tank
and the side and rear property lines (set backs).
d. providing verification that generator will be installed at current base flood elevation
or above per FBC 3110.1.2 and FBC R301.2.4 FEMA.
Note: Mechanical equipment and generators cannot be closer than 5’ to the property
lines and 10’ to the water. Equipment can be no larger that 40 sq. ft. in area and
5’ in height.
5. A Building Permit Application is required if a slab is to be poured:
a. if the slab is existing or “prefab”, a building permit is not required.
b. the slab must be a minimum of 4” thick and comply with standards set forth by
FBC 1820.5.
c. specifications for generator anchorage for wind loads per FBC 1612.1.2.
Note: It is the responsibility of the contractor to verify that the soil bearing capacity
will support the slab and generator.
6. If natural or LP gas is used, a Plumbing Permit Application is required from a licensed
contractor.
7. Two(2) Isometric Rise Diagrams with plan view:
a. showing total length and type of piping and chart used to size gas system.
b. showing generator BTU rating.
8. If a non-self contained diesel fuel generator is proposed, a Mechanical Permit Application
is required. In addition, the plan showing diesel fuel holding tanks must be approved by EDP.
Note: Portable generators will be reviewed on a case-by-case basis.

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That all seems pretty typical for a populous area. When you have a lot of people closely packed together, any corners you cut become an endangerment to others, and that's where your "freedom" ends in a civilized society.

twistedtree said:

That all seems pretty typical for a populous area. When you have a lot of people closely packed together, any corners you cut become an endangerment to others, and that's where your "freedom" ends in a civilized society.

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As it should, I think. Our contractor had no problem complying as the rules are well known locally. The generator suppliers even refer to one size as their Fort Lauderdale model, jokingly, as it's the largest legal here.

CMS said:

This is an unsafe and dangerous installation, if that is what happened..

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I failed to unplug... My error entirely after a year plus on the hook. I have a visual now though the 1k is now out of the system.

My AIMS1000 has three outlets to plug in items. Instead I took one cord and wired it into my AC panel. The plug part goes into one outlet on the inverter. Thus the whole boat has power available. The flaw was my user error. When I docked I should have shut off inverter AND unplugged that cord. Operator error for certain.

Since then, for maybe four years or so, I had a visual on the 30amp inlet of Seaweed. I recently "put to bed" the 1000 because I upgraded to a 1200. The old square wave is not in service. At some point I will probably swap it for something I want more...

I have a pure sine wave inverter now. It automatically switches on and off though I have a remote to shut it down manually.

Janice, it seems the problem is in the plug-in connection you make and the hard-wired output you have to your AC panel. Having two AC sources feeding the panel simultaneously is dangerous. A switch that controls the power from only one source at a time would help. Know any friends with marine electrician skills?