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Thread: Best battery for Home Inverter system

  1. #1

    Default Best battery for Home Inverter system

    Hello gents, I am looking to fabricate a home inverter system to run a fridge and some lights during an emergency. The type of inverter I am looking at is a pure sine wave type approx 5000 watts. My question is what is the best battery to use? I will probably keep it on a trickle charger to keep it at 100% and I would probably keep it in the garage. I do not think lead acid is the best choice as from what I understand its not recommended to use them indoors (even a garage). I would like to have the longest run time available. So what are my choices? Gel Cell, Marine Battery (is this lead acid?).

    Thanks--Aristotle

  2. #2

    Default Re: Best battery for Home Inverter system

    You probably want a deep cycle battery. The various online inverter vendors should have batts available along with their inverter products. 6V golf cart batteries also work well. You have to put them in series to get the voltage up to 12V or 24V or whatever your inverter needs.

    Realize that to go from 12V to something like 120V/15A for a fridge circuit means that your wire connection from the batts to the inverter need to be able to handle on the order of 100A or more. So you have to get the right gauge cabling. Romex or lamp cord won't cut it. Also make sure that your inverter can handle the startup load from the fridge.

    How do you plan trickle charge the batt/batts? Separate charger, and then you disconnect the batt from the charger and connect to the inverter when you need it? Or are you going to get a pure sine wave inverter/charger setup?

    What run time are you trying to achieve? A single deep cycle batt probably won't give you long run time. You could parallel multiple batts together, although there is some risk to that if one batt goes weak. You could get a 24V inverter, easing the current draw a bit and allowing you to go with something like 2S2P if you use multiple batts.

  3. #3
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    Default Re: Best battery for Home Inverter system

    what he ^ said, with a 5000w inverter you dont need a battery, you need a bank of batteries to get an ammount of time https://www.google.com/search?q=alli...w=1198&bih=702. it might even be more practical to "invert" your thinking , and use way more efficient items, and/or things that run slower lower and or on lower voltages/amperages during an emergency. Like 12V fridges, and led or CFL lights, some backup systems have seperate lighting for the backups, way back when (~1960) they would have 12v incan bulbs and 12v seperate wiring to deal with that, today we have many efficient things that can replace the hogs.

    compressor motors are very hard to start, but 5k whould pull it off.
    I calculate ~300Amps at a low 12V would be needed for ~3500w pull that is some serious storage, and some serious cables. assume that somehow you could pull the 3500w from a 12V battery, it would be like continually trying to start a 8 cylinder gas hog, as the starter motors for big engines use that ammount of power at thier peak.

    Gells. marine batts are lead acid, and unless you have 10,000USD to build a specialised ni-mhy or lithium system (like a 'lectric car) lead acid is the only way to do that kind of power for any lenght of time.
    You will basically be having a storage system that is Very Very similar to a solar system that has battery storage , and that would be a good place to get information.

    Yes the lead acid batteries when charging (but mostly when overcharging) let off hydrogen gas, and (i am pretty sure) let out the oxygen too (seperate the water) , and that gas mix loves to recombine given any ignition source, which can include pilot lights and sparks.

    A "battery Bank System" has some sort of ventilation and safety for that aspect of it to insure that does not happen. or is in a box outside, many different methods, and some people use like no methods :-) to insure that aspect of it. It is possible to put them indoors with some of the venting methods used, either crazy enough, or having it worked out well enough. many garages are not very tightly sealed, and making ducting and venting, or even sparkless fan venting is all possible and done to solution the gas issue. which still leaves the fact that these things are full of acid.
    Last edited by VidPro; 07-21-2012 at 11:05 AM.

  4. #4
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    Default Re: Best battery for Home Inverter system

    The simple and best (as well as cheapest) solution would be to purchase a proper generator.
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  5. #5

    Default Re: Best battery for Home Inverter system

    If you are going to run 5000 watts, you'll need at least 4/0 gauge cables to connect the batts and inverter.

    The typical battery type used in these applications are deep cycle, sealed lead-acid, AGM. They should release minimal gas due to oxygen-hydrogen recombination. Make sure you don't abusively re-charge the battery. If you get something like a 200+ Ah deep cycle batt, it should be able to deliver any current draw that your inverter will demand. To run some simple calcs, if your fridge draws 1000 watts when running, and it has a duty cycle of 25%, then one 200Ah batt can run the fridge for about 12V*200Ah/1000W * 4 = 9.6 hours. I'd probably reduce that 9.6 hour figure in real life since even the deep cycle battery probably won't like getting discharged to zero SOC. Let's try 80% discharge depth, or 7.7 hours. Let's round that to 8 hours. If the duty cycle is 50%, the run time drops to 4 hours. If you parallel four of these batts together, your run time at 25% duty cycle for the fridge is ~32 hours.

    I'd probably put an inline fuse between the charger and Batt+. Maybe also a cutoff switch.

    An inverter-charger with built-in transfer switch would allow automatic switching between grid and backup batt power to keep your fridge running, and charge the batts off of grid power so that the batts are ready when needed.

    The setup adds up to a lot of money. Why not something like a Honda EU3000is generator instead?
    Last edited by Justin Case; 07-21-2012 at 03:58 PM.

  6. #6

    Default Re: Best battery for Home Inverter system

    I have a inverter with a deep cycle battery. It works great and I can continue to have lights and TV etc. But to power larger equipment a big cash outlay is needed. My father wanted to go this route but I talked him out of it. He would have needed at least 4 batteries in parallel. 4 batteries cost as much a 2X 3500W generators, when they are on sale which happens a lot. Yes its not Honda generators but it works well. He bought only one and really it was cheaper than what just 2X deep cycle batteries would have been. Then you must also take into account the cost of the inverter, which will be quite a bit of money. Then all the trickle charging/maintenace and replacement of batteries as they don't really last that long, at least not with me.


    I don't know your setup but my father put his generator in a shed about 20m from his house, therefore its gases and noise are no problem. He had an electrition to integrate the system into his house's power grid and its just a flip of the switch to go from city power to generator power. He can therefore use all the plugs and lights just like he is normally using it. But heaters are not used, the geiser is switched of and only one plate of the stove is used at a time. He can also use the kettle etc. If your situation allows it, you will be much better of with a generator.

  7. #7

    Default Re: Best battery for Home Inverter system

    What you need is a bunch of NIMH D cells..... about 6500 of them!
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  8. #8
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    Default Re: Best battery for Home Inverter system

    That last time I looked at 5 KW inverters, most were designed to run from 36 - 48 volts, which sort of makes sense when you think about it. At that time, the battery packs that made the most sense (for me) were the fork lift batteries.

    This is not a small setup, but I do understand why you are interested in it. The place to look at inverters is through the solar related distributors. There are some pretty clever systems out there that will combine whatever power generation is available (solar / generator / grid ) to keep the battery fully charged, and then invert it for use, as needed.

    None of this stuff is small or cheap, but it can make sense depending on your situation.

    One of the great tragedies of the electric cars on the market, esp. the Volt, is that they have not included the concept of using that massive battery pack / generator capability for emergency home power use. That feature alone would make me consider a hybrid car, but without it - forget it. I think that either Chevy or Ford had a pick up truck on the market for a while with 120 V outlets on it, but I can't remember which one.
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    Default Re: Best battery for Home Inverter system

    It is interesting that you are targeting a pure sine wave generator, because I actually was at the semicon west / intersolar show a few weeks ago, and it was full of inverters.

    I couldn't help but wonder though if it would be easier to just connect a 12 V motor to a 220 VAC motor to produce sine wave power ?
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  10. #10

    Default Re: Best battery for Home Inverter system

    Yeah, Deka makes some pretty beefy 36v fork lift batteries that would be nice for this application.
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  11. #11
    Flashaholic Aquanaut's Avatar
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    Default Re: Best battery for Home Inverter system

    I bought a top of the line water cooled Honda 5500 watt generator over 25 years ago, and it is still running like new. I use it several times a year due to power outages to power my entire house. The last outage was for three days. I shut the generator down overnight. My refrigerator and freezer will stay cold enough to avoid spoilage for 8 to 10 hours. I keep gas store in the fuel tank. I highly recommend "seafoam" for gas storage. My generator has sat for over a year with absolutely no attention, and it will start right up. I wouldn't even consider a battery/inverter setup.
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  12. #12

    Default Re: Best battery for Home Inverter system

    The Honda EU3000is is rated at 2800W max and runs for about 20 hrs on a tank of gas (3.4gal, 1/4 load). It is very quiet -- under 60 dB. If you want more power, you can parallel the EU3000is with another EU3000is for 5600W. However, if you do just a bit of juggling with appliance demand, you should be able to run a fridge, microwave, lights, and room AC with one unit. You just can't run them all at once. But there is most likely no need to do so.

    The inverter and battery setup could be useful if you had a solar setup to re-charge the batts. A generator could also re-charge the batts.

  13. #13
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    Default Re: Best battery for Home Inverter system

    Quote Originally Posted by Aquanaut View Post
    I bought a top of the line water cooled Honda 5500 watt generator over 25 years ago, and it is still running like new. I use it several times a year due to power outages to power my entire house. The last outage was for three days. I shut the generator down overnight. My refrigerator and freezer will stay cold enough to avoid spoilage for 8 to 10 hours. I keep gas store in the fuel tank. I highly recommend "seafoam" for gas storage. My generator has sat for over a year with absolutely no attention, and it will start right up. I wouldn't even consider a battery/inverter setup.
    That's what I'm sayin'. No bank of batteries will EVER replace my generator...I live in the heart of hurricane country!
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    Default Re: Best battery for Home Inverter system

    Battery banks are good only as short-term backup and/or low power backup for security systems, UPS for computers to bridge short power outages and prevent unexpected shutdowns etc... For longer power outages (like your hurricane season etc) is generator a must! But here in Europe we A) don't have hurricanes and B) we have power lines in cities mostly in ground - so falling tree is not a problem. The longest power-outage I remember was around 8hours but it was scheduled maintenance. Other unplanned outages are around 1-2hours max so I can live even without generator just fine.

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    Flashaholic* mattheww50's Avatar
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    Default Re: Best battery for Home Inverter system

    As a practical matter, a 5000 watt inverter from a 12V source is the height of impracticality. The losses in the wiring are I^2 x R. Once you get past 100 amps, I^2 gets to be a very large number.
    So for example drawing 400 amps with .01 ohms in the wiring entails the loss of 1600 watts! As an electrical Engineer I will tell you it is tough to get the wiring resistance down to .01 ohms.
    By going to 48 volts you reduce the current to about 100 amps, and that same .01 ohms is only 100 watts in losses. Because I^2 is such a big number, the rule of thumb is to always try to
    keep the current under 100amps when possible. The very high current also means you are going to spend a lot of money for copper. Copper wire that large is both expensive, and hard to
    work with. As another poster points out, the recommended copper wire size for that current is 4/0. 100 amps means much smaller gauge copper, which is both less expensive, and easier to work with.

    If you really need 5000 watts, you are looking at a very hefty investment for both the battery pack and the inverter. A generator is a much more practical solution.

  16. #16

    Default Re: Best battery for Home Inverter system

    I would suggest that you buy a small 12v refrigerator that is designed for 4 wheelers to carry with them. Use a small solar array to keep the AGM batteries charged. You can transfer your best food to the small refrigerator. A generator is also a good idea. Get a good one.

  17. #17

    Default Re: Best battery for Home Inverter system

    4/0 gauge is about 0.05 ohms per 1000 feet. If you had a 2 foot long run, the resistance in the cable would be (1/500) * 0.05 = 0.0001 ohms. If I=400A, the I^2R loss is 16W. I'm not sure why you think there is a problem regarding wiring resistance. Use the proper gauge and keep the runs short.

  18. #18
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    Default Re: Best battery for Home Inverter system

    The problem at very high current is usually the connectors/connections, so while the resistance of the 4/0 wire wouldn't be a problem, the resistance in the connectors probably would be. That is why it is so tough to get the resistance down to anything on the order of .01 ohms. The connectors need to have enormous surface area, and be protected from oxidation. This tends to be difficult. Suppose
    each connection is .001 ohms (hard to achieve). At 300 amps each connections still has to dissipate 90 watts. The result is heating, and unless care is taken, corrosion usually occurs, raising the resistance still further,which makes local heating problem worse. It can be a vicious cycle!

    Keep in mind you also also to connect the individual batteries in the system, and 4/0 wire is pretty hard to work with, the result is you are likely to end up with a whole lot more than 2 feet of the stuff. Even at 12 volts, you would need to make at least 4 connections, two each at the battery and the inverter. It really pays to raise the voltage and lower the current. Doubling the voltage halves the I^2 x R losses.

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    Default Re: Best battery for Home Inverter system

    a big lead acid bank
    is the best for this application, since weight of the batteries is not an issue (not moving or carried)
    keep them topped off with a serious solar array

    Yes... have generators and inverters, but if the crap really hits the fan what do
    you do when your 450 gallon tank of diesel runs out ?
    Last edited by 127.0.0.1; 07-23-2012 at 08:19 AM.
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    Default Re: Best battery for Home Inverter system

    Quote Originally Posted by 127.0.0.1 View Post
    a big lead acid bank
    is the best for this application, since weight of the batteries is not an issue (not moving or carried)
    keep them topped off with a serious solar array

    Yes... have generators and inverters, but if the crap really hits the fan what do
    you do when your 450 gallon tank of diesel runs out ?

    It all depends on what you're planning for. I can spend $1000 on a generator and power switch installation, get some gas and stabilizer, and be set for a few days worth of not suffering.

    A solar array to run a normal fridge and appliances (Call it 24 kWh per day, US average last year) would be massive. I think I could put a few hundred watt-hours per day on my roof if I spend tens of thousands of dollars. If the excrement really does impact the oscillatory air mover (In a way to put power and go-get-gas infrastructure out for weeks) there are things to worry about besides mere electrical power. tl;dr, for infinite duration solar power may be better, but then it's a different question than "For power outages."
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  21. #21
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    Default Re: Best battery for Home Inverter system

    PV solar is a huge up front investment, but it can eventually pay for itself in the form of cost savings. I'm not sure what the interest rates on loans are these days, but it might be something to look into if you're considering going this route. Some PV solar installation companies will likely also offer financing options. Make sure you get your setup covered under a reliable insurance plan too.

    Fuel powered generators are still initially much more cost effective. So if this is only a once in a while to use as backup kind of setup, then that's probably the most cost effective way to go, but don't let me dissuade you from going solar.

    Getting a Pb setup with high enough capacity and voltage (if you go that route, but remember Wh is what you want to look at for energy storage, not just capacity, of course) would be pretty expensive too. Keeping them topped off and maintained properly will require some maintenance now and then too, and of course they don't last forever.
    Last edited by Wrend; 07-23-2012 at 09:59 AM.

  22. #22

    Default Re: Best battery for Home Inverter system

    Google Nickel-Iron batteries. I have off-grid soalr power system with nearly dead old salvaged Lead-Acids,planning to replace with nickel-iron.

  23. #23
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    Default Re: Best battery for Home Inverter system

    I have an APC 2200VA UPS in my basement for exactly the same reasons the OP is talking about. It is a 48V system and accepts external batteries. I currently have two banks (4 12V jars each) of ~90AH capacity each on it. Each bank is fused at 100A between the middle two jars, and I can unplug each for maintenance via Anderson connectors. These are like 80# batteries and I have eight of them in the basement, on a crawlspace ledge. They are AGM SLA batteries and perfectly safe in this application.

    I also have an EU2000 generator that I can plug the UPS into in an extended outage. My dryer vent is short and right by the UPS so tossing an extension cord in from outside is super easy and convenient.

    The UPS is wired to my two computers and tv/entertainment system. In that configuration it'll run everything for about 12 hours. It has enough capacity to connect my chest freezer and kitchen fridge also with no problem. It is kinds fun when the power goes out in a big storm and I can sit and continue to watch the news and either wait for power to come back or once the weather clears to pull the generator out (which I've only had to do one time now).


    anyway.... I think 5kVA is well oversized for just lights and fridge and stuff. And yes, pure sine is what you need for a fridge. My APC is that. Check craigslist and/or ebay or ask any computer people you know, These type unit can often be had very cheap with dead batteries in them, which you won't use anyway because those batteries are so small in capacity.
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  24. #24

    Default Re: Best battery for Home Inverter system

    If a person is worried about refrigeration which would be on of the largest draws in a power outage, you might consider getting a 9.9 cubic ft propane/Ng frdige. A Servel runs off both 110 volt and propane/Ng and it will last about 2 1/2 weeks on a 20 lb propane cylinder. No worrying about long term gas storage. Drawback is they cost around $1100. Dometic is another excellent brand.


    For batteries, most folks off grid use to use Trojan T-105s or US 2200 6 volt deep cycle batteries(run in series parallel to make correct voltage and amp hr storage). They take much, much more abuse than an AGM will and are best suited to folks who haven't run battery banks before. Ours(US 2200) lasted 6 years of heavy abuse and we now use them at or cabin. I highly recommend against getting marine batteries.

  25. #25
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    Default Re: Best battery for Home Inverter system

    Does anyone even make a 5500 watt Inverter that runs off 12 volts ???

  26. #26
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    Default Re: Best battery for Home Inverter system

    It does not take as much power as most think just to run a refrigerator and a few low power light bulbs. I have monitored my refrigerator over a year now. It runs most of the time and varies from 90-135 watts ( voltage irrelevant) I put a 35 watt headlight on 2 X 6 volt golf cart batteries for over 2 days trying to run them down and they held out for 48 hours.

    Its not unreasonable to shoot for 48 or more hours minimal power usage on a set of 4 full sized lead acid batteries. My fridge averages 2.7kw per day. The 1.2kw-1.5kw batteries are not uncommon. A set of 8 batteries @ around $1,600 total should run you 3 to 4 days if you are really frugal.

    Personally , I just keep extra gasoline on have for my welding machine that has a 10kw generator. Downside is that it consumes a minimum 1 gallon per hour and more on a heavy load. I figure on running it intermittently as needed only but you could do the same thing with battery power.

    BTW: The refrigerator mentioned is a 22CF high efficiency.
    Last edited by lwknight; 08-05-2012 at 07:05 PM.
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    Default Re: Best battery for Home Inverter system

    I am very impressed that people have such good luck with their honda generators. I can tell you this, my experience with using their lawn mowers is less than stellar. I have pretty well confirmed now (after years of trying to figure it out) that the carb is not compatible with gasoline that contains ethanol, and when used on a small yard / low consumption situation, it is a poor choice.

    If you really need long term power after a hurricane, then consider to buy a gasifier + matching generator, and skip the liquid fuel approach. You can load them up with wood scraps, and produce 5 - 10 KW as needed, no other fuel required. Example, gekgasifier and there are others out there. I was surprised how well this concept works.
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  28. #28
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    Default Re: Best battery for Home Inverter system

    Concorde AGM ( http://www.sunxtender.com/ ) driving a Prosine 2000w or 3000w inverter. These have charger and transfer switch built in, good peak power and lot's of battery protection built in.

    See; http://www.hearth.com/talk/threads/b...2/#post-149743 for an example I built.

    I have a Solar (5.2kw) powered grid tied system with battery backup. The inverter is 5KW with 7KW peak for motor starting, the battery bank is 8-8D 12v 250amp batteries wired as 48v 500amp 24kwh. This gives me 12kwh of usable power. This will run most of the house, for just a fridge 5Kw is not need as long as the inverter has peak power for motor starting.

    Gasifier require dry wood, after a hurricane there is not much dry anything. Just like going camping with solar power system no sun no power like it's cloudy, rain or your camp is in a redwood forest with 100+ foot trees.

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    Last edited by Kilted; 08-08-2012 at 11:57 PM.

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