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Thread: simple battery bank system for a cabin

  1. #1

    Default simple battery bank system for a cabin

    I am bulding a cabin and want to install a simple batterie system. I'm thinking 4 rv batteries anyone ever do this how long will a charge last? I just want to run a coupple of lights, tv/radio. any suggestions would be appriciated.

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    http://www.alternate-energy.net/calculateamp02.html

    there is a list of tools on this site to calculate things like battery bank run time.

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    Member mainer_in_ak's Avatar
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    There are specific batteries for a power storage bank, inverters, and charge controllers for off grid power. there is an actual store in anchorage that sells the batteries, the inverters, and the controllers. You can actually set the bank up to be charged by wind turbines......and the generator too. with generators, try to go with a small diesel model in the 3000-6500 wattage. Really good generators on the upper end will run 1,800 rpm. If they run 3600 rpms......they aren't all that great for long term reliability. Usually though......an 1800 rpm gen. will cost about 6,000 dollars, a cheaper 3600 rpm diesel gen will be between 2,000-3,000 dollars. Northern lights has a 6000 watt, 1800 rpm gen for about $6,500. Whenever you need a big load (powertools, washingmachines, etc). Turn on the generator going to the batteries.....that way there all the fuel is being used efficiently by both charging your batteries and providing you the extra power supply for the demanding load. If you do get a cheaper 3,600 rpm gen.....look for a HATZ or YANMAR diesel. they will usually burn about .2 -.4 of a gallon per hour......and they love a full load. The Yanmars, and Hatz motors are mated to a very precise computer and electronics freindly alt. much more efficient than a gasoline gen., and they last alot longer too. If you need any info about generators....pm me, i've hooked up dozens of remote units over the years. I especially like the northernlight gens......they last forever! (with oil and filter changes).

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    Quote Originally Posted by loose moose View Post
    I am bulding a cabin and want to install a simple batterie system. I'm thinking 4 rv batteries anyone ever do this how long will a charge last? I just want to run a coupple of lights, tv/radio. any suggestions would be appriciated.
    Your batteries will last longer if you think ahead and add some 12v lighting where you'll use battery lights the most. They'll drain less power than 120v lighting operating through an inverter. I even had a 12v TV and VCR before the new digital signal made them obsolete. But the flat screen that replaced it is easy to power off of a very small point-of-use inverter. So, to your question? The sum of your stored amps will only last until you use them up. How long that'll take is impossible for anyone to predict. I can say that 4 fully charged batteries in series will run a few lights and a television for quite a while if the inverter and appliances are efficient. But 4 batteries will also take longer to charge. You need to strike your best balance between storage capacity and recharge time. How you use your battery-powered appliances and how you use your generator are unique to you. There's no "one size fits all" answer.

    A few tips. 1) Use deep cycle batteries. You can get 6v golf car batteries at Sam's Club and connect them in series/parallel. Good storage capacity for the price. Two batteries will run your stuff pretty well. Make sure your battery charger is properly set for deep cycle and has the output to recharge in a reasonable amount of time. 2) Beware of noisy inverters. Most have built-in cooling fans that are louder than you'd expect, even the little ones. For small inverters I like the Duracell brand. They're still made by Xantrex, the big boys in the inverter business, but this particular brand is silent to operate. Very nice late at night when the TV volume is low. They have digital battery bank voltage meters built-in, too, so you'll know when you need to crank the gennie. You can get Duracell inverters at Best Buy. 3) Expect condensation on the batteries. It'll ruin your cabinet or floor if you don't do something to catch it.

    If you're going with a higher output inverter you'll likely get a built-in charger, but if that's what you're doing the system is more complex than what your post described. Built-in chargers require bigger generators. Small systems do not. There's nothing wrong with a couple of deep cycle batteries hooked to a typical automotive charger with an inexpensive inverter to plug your stuff in to. I did it for lots of years before I jumped into a big system.

    Good luck.

  5. #5

    Default Power

    Your power storage needs can be better met with the use of 4 golf cart batteries versus 4 RV batteries. The golf cart batteries are better electrical storge devices( holding more amperage and allowing more charge/discharge cycles). The cost is slightly higher with golf cart batteries but they last longer and the overall cost would be the same. There are larger storage batteries that are usable as well depending on your needs, but these are a stating point in power storage.
    The bigest difference would be if you have to pack them in as golf cart batteries are 20-25% heavier than conventional group 24/27 RV batteries. The best are made by TROJAN followed closely by EXIDE then come the rest of the battery makers. However once you get into the larger battery banks there are a lot of HEAVY duty and quality brands.
    IF you intend to use power only for lights and a water pump or small daily uses ( PC, TV,radio) I wouldn't use an inverter. Inverters are at best around 90-94% effecient across their power spectrum. The use of 12volt throuhout the cabin would make more sense. All of the commonly used items are available in enery saving 12 volt configurations. Then just use a small inverter for intermittent use of a TV-DVD player.
    When you discharge your batteries STOP around 12.2 volts and start recharging. AT 12.2 volts a battery is down to 50% power storage and any deeper discharge can cause damage and shorten the battery banks useful life.

    Also remember that 12volt systems should be wired in stranded type wire not Romex as is used in 110 volt houses on the grid.
    Your charging system should NOT exceed 15% of your storage capacity of your storage capacity.
    IF you are considering a wind charger check the annual wind charts in your cabins area for the viability of such a purchase. SOME ares have poor winds and wind chargers just become YARD-ART.

    Also remember that 12 volt systems should be wired in stranded not solid Romex as houses on the grid are.
    Last edited by brav01; 09-10-2009 at 08:19. Reason: left out
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    Quote Originally Posted by brav01 View Post
    Also remember that 12 volt systems should be wired in stranded not solid Romex as houses on the grid are.
    Brav01:
    Very good post. I do not understand the reason for using stranded wire in a cabin. There is no vibration in a cabin and the dc resistance of a stranded wire is the same as a solid wire.

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    Mr. Pid,

    good call on that duracell inverter. they are electronics freindly "true sene wave". They are made by Xantrex, and the duracell line of inverters are availible all the way up to 3000 watt. Everybody knows that Xantrex inverters are excellent quality.....as well as there 40 amp charger.......one of the fastest chargers for the money. With that said, you have to plan your electrical system for the future. It's more important to spend the money and do it right the first time than to spend too much extra money upgrading to a larger off-grid electrical system.

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    Default Solid vs Strand Wire

    The reason you need to use stranded wire in a DC system is because DC current travels along the outside of the wire whereas AC current travels thru the wire. In a DC system you need to maximize the outside surface available which means stranded. An inverter run off of batteries will end up being less expensive due to cheaper wire but also much cheaper fixtures. Probably the best local source for materials and advice is ABSAK Electrical in Anchorage, 907-562-4949. I bought mine from them and their advice was great.

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    loose moose,

    Don't get intimidated by all the info about inverters and batteries. You want simple? For many years I used a trolling motor battery with a car battery charger clamped to it. For output I had a Costco el-cheapo inverter. Whatever was plugged in to the inverter ran off the inverter whether the gennie was on or not. I ran the TV, VCR, CB radio, and a light from one battery. I never ran out of juice that I can recall. Add a small solar panel and you can eliminate the generator for all but the darkest months. My system worked great but I graduated up into a more comprehensive system as the family grew. I have several friends who still use the simple systems today without any problems. Probably the most important rule is to determine how much peak power and storage capacity you really need. Buy the appropriately sized componenets for those needs. More is not better if you don't use it. More is just more expensive. Keep the batteries charged and they won't freeze. And in all cases, a warm battery out-performs a cold battery. That applies to input and output power.

    On-site power systems will make you a power conservationist.

  10. #10

    Default System

    Keeping batteries warm is a good idea; however keeping conventional lead acid batteries in a cabin can cause the production of flammable hydrogen sulfide gas in enclosed spaces, "IT STINKS TOO". The off gassing is a by-product of batteries charging. When you mount your inverter or other electrical equipment it shouldn't be directly above the battery bank as these gasses are corrosive and can damage or cause corrosion. A fully charged lead acid battery (12.8 v) doesn't freeze until -93* they do however have a self imposed shelf discharge rate. This rate varies with battery brands and as the batteries charge level goes down so does its ability to witstand cold.
    AGM ( sealed) batteries don't off gas but have a slower power release than conventional batteries. They (AGM's) also need to be charged slower and are much more expensive than their conventionally sized lead acid couterpart. They do however freeze at the same rate as lead acid batteries based on charge rate. Batteries are the expendable and most replaced part of an electrical system; either due to growth or just daily use.
    SIZE matters and too big is TOO BIG. Your system should have a surplus of about 15-25 %.
    If you plan to expand your system some components should be purchased with the end goal in mind, thereby saving money on the overall finished system down the road.
    " Americans will never need the 2nd Amendment, until the government tries to take it away."

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    My limited understanding of stranded vs solid wire for lower voltage DC systems is that the amperage for a given load is higher in lower voltages which causes more problems with heat at connections with is exacerbated but the tendency to have poorer connections at terminals unless proper connective appliances and methodology is implimented.

    One website article describes it this way.

    A 120 watt load draws one amp at 120 volts a.c.

    That same load would draw ten amps at 12 volts d.c.

    With solid wire you can not get the intimate contact between two
    wires nor at the connections on a device (switch, etc) or load.


    With stranded wire you get more intimate contact, thus reducing
    voltage drop and power losses.
    Poor connections can rob a system of a significant portion of the
    power being produced.

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    regarding the actual batteries.......One of the best performing batteries in cold weather and long charge/discharge life are the AGM batteries (absorbed glass matt). There are numerous AGM battery brands. One of the top dogs out there are the Concorde brand batteries. What makes them one of the best is that they have bolt style terminals as opposed to the regular automotive and marine style terminals. Because the paticular model battery I'm reffering to will not see automotive/marine use (even though it is identical to the other models)...........the warranty is cheaper....therefore the overall price is cheaper. I believe a 100 amp will run about 200 dollars and a 220 amp will run about 450 dollars.

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    In 10 years the only time I've smelled any off-gassing is when I was equalizing and that's because I remove the condenser caps to do so. My wife has the nose from hell around any chemical fumes. I guarantee she'd complain if there was any sulpher smell!

    FWIW, I use Exide L-16 batteries in series/parallel to push a Trace DR2412 inverter. A friend has an almost identical system except he uses Rolls-Surrette L-16s. His batteries are better than mine. No question.

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    With all do respect you have it reversed. DC resistance is the same in a stranded or solid wire.

    What you’re talking about is skin effect, the faster a frequency moves through a wire the farther it is from the center, DC does not change amplitude (frequency= 0) . If you looked at coax cable, skin effect is not a consideration when determining size. Also if you measure the AC resistance of a wire be it 10 ga. (stranded or solid) or 3/0 (stranded or solid) the AC resistance @ 1000 hz. is = to the DC resistance.

    Or

    DC resistance = E/I
    There is no mention of stranded or solid wire in the formula for DC resistance.

    Mics 54:

    Everything you say is correct; it just does not answer the question that stranded wire is better than solid wire in this application.

  15. #15

    Default GAS

    Many batteries have hydro-caps or caps which stop batteries from off gassing or boiling out electrolyte. These caps also stop the electrolyte from spilling if the battery is inverted as in airplanes. These are available for nearly all styles and types of batteries.
    Concorde does make hi quality batteries and these are used in off grid systems. The Concorde PVX-1040 12v@100 amp costs about $289.00 that's almost the same amount as 2 Exide golf cart batteries @ $148.50 ea. It is however only 1/2 the power storage of 2 Golf Cart batteries, for the same dollar.
    There is also a battery size or 2 between the Golf Cart Batteries and the L16. The most common are floor sweeper batteries; FS 6 size.

    As far as stranded wire for DC use, I'm not sure why it's used. BUT, I believe it's listed in NEC as code.
    Last edited by brav01; 09-10-2009 at 12:25. Reason: left out
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    moose
    Everything you say is correct; it just does not answer the question that stranded wire is better than solid wire in this application.
    I believe it's the authors position that stranded was preferd because it was easier to get better connections thus decreasing power loses and reduce heat which is more inherant in lower voltage systems.

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    My 12v wire that runs from the distribution box to each fixture is simple 2 conductor lamp cord on a bulk spool I picked up at Frigid North. Except for one circuit where I used monster speaker cable, lamp cord has been more than adequate, easy to hide, and cheap. My 12v distribution box is from Alaska Battery Mfg and uses plug-in automotive fuses. Very tidy.

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    Default Bad gas

    If you have your batteries inside and smell sulfur, then you likely have a problem with your charger. We've got three 12v RV/marine batteries in our 12'x16' cabin and never smell anything (from the batteries anyway). Excessive off-gassing is usually caused by overcharging. Ideally, you want a 3-stage charger that automatically cuts back on the amps being feed into the battery bank as it becomes charged.

  19. #19

    Smile thanks for all the info

    I am now just wiring the cabin and will do a little more home work on the system I want before i invest the money untill then i will run on gen power. thanks for all the info

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    Quote Originally Posted by Mr. Pid View Post
    My 12v wire that runs from the distribution box to each fixture is simple 2 conductor lamp cord on a bulk spool I picked up at Frigid North. Except for one circuit where I used monster speaker cable, lamp cord has been more than adequate, easy to hide, and cheap. My 12v distribution box is from Alaska Battery Mfg and uses plug-in automotive fuses. Very tidy.
    What did you use for fixtures and switches? I like simple. Ever use 6 volt Trojan batteries? Like in a man lift?

    Sorry for the questions. I like the quiet of batteries and hate the generator late at night. I would prefer using the generator for a couple hours in the AM for coffee and a charge on the batteries, then quiet for the evening.

    I have a 1700W generator. Basically a smaller Honda 2000. Still too noisy for me.

    Can a guy use a normal circuit breaker panel with 110 wiring throughout?

    Common uses:
    1000W halogen lights for getting in on a Friday night, 1 hour.
    4 60W lights and possibly a stereo in the evening.
    1000W Microwave and other short use appliances.

    Thanks,
    Mike

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