Off grid battery bank question.

Discussion in 'Off Grid Living' started by Frozen2death, Dec 20, 2016.

  1. Frozen2death

    Frozen2death Monkey

    Hello all, I guess this is a introduction as well as an advice post. I live here in alaska, I am a plumber and a jack of all trades been in constuction since i could piss , I have been lurking on the forums for awhile absorbing all the information I can here.
    I have some challenges that I could use some advice on so I'm just going to start.

    I'm building a new house for me and my family heat will be wood stove backup Toyo, I will have a well with a normal 1/2 hp pump that I have a big boy gas hog generator to pump water into a 500 gallon holding tank which uses a 60psi dc pump to pressurize the water system in the house (single bath, kitchen sink). Now my plan is to run a Honda 3000is to power the house which if everything is on and powered (TV, low watt microwave, led lights, DC pump, low watt fridge, misc small electronics,) I'm looking at 2500 watts give or take with the fridge and microwave, obviously not running 24/7.

    Now to the fun stuff I will have a 24v battery bank, around 10 12v 100amp hour batteries wired to 24v, with a 3500 watt pure sine inverter giving me on paper 500amp hours I am figuring loss of 100amp hours just to play it safe so I'm just saying 400 amp hours, which is more then enough to run my system for a day, now the question, should I
    A: run the house system off the generator while the generator also charges the bank then switch to bank power,
    B: Run only the bank power 24/7 and only charge with generator will this work?

    C: Run the house off the generator and use a smaller 1000watt to charge the bank system and when charged switch to battery bank. Like I said when I get more money together I'm adding solar but I'm building the house out of pocket and have set limits on money right now.

    I understand the cost of fuel and this system, what is the best way for me to power my house any other ideas, I greatly appreciate any help or advice that you take time out of our day to give.
    Last edited: Dec 20, 2016
    Yard Dart likes this.
  2. Yard Dart

    Yard Dart Vigilant Monkey Moderator

    First off, welcome to the forum... glad to have you here!!
  3. Frozen2death

    Frozen2death Monkey

    Thank you :D
  4. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Have You bought all this stuff before you ASKED ??
    CUZ that cell layout is math out.
    Whos puresine ? Post pix & real info on this Plus where are you living now & washing by ??
    How big is the fam ? & if your paying for power , post your power bill specs

    Sloth & welcome
    Last edited: Dec 22, 2016
  5. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Ok, I live out in the Bush of Alaska, and have run a similar System, as yours, for two plus Decades... Looks like you have most of the things figured out... I would start off FIRST, by looking around for a Diesel Genset. Preferably one that turns at 1800, or 1200 Rpm... You can find used Onan Diesel Gensets,for easily less than a Grand, if you look around... With Good Routine Maintainance they will outlast ANY Honda, or other Gasoline Fueled GenSet, by double, at less Fuel Costs, per Kw Generated... Your Domestic Water Storage should be inside an INSULATED, Heated Structure, or I would suggest you look for a Stock Tank Heater, for it, so you don't waste the water, as Ice, in the Winter. Some of my neighbors put their Water Storage, inside the Insulated Attic space, in their Cabins, so that it stays above Freezing, using Cabin Heat... If you care to share other details via PM (OpSec Rules around here) I would be happy to chat, about what I know works...
  6. Frozen2death

    Frozen2death Monkey

    Thanks for responding:p
    No have not bought the equipment yet.

    Pure sine wave is a voltage wave form not a brand that has very low harmonic distortion unlike modified sine wave which you would get from say just a standard generator. It provides a wave length close to the utility company. I have not picked a inverter yet but I am looking for the most efficient.

    My current energy bill is null because my heat, water heater, dryer is electric but I am using about 1400kwh a month, and am humbly wasteful about it. New house will have only led TV using 128, low watt led lights, DC pump, low watt microwave and fridge and misc small electronics. I will be washing at home with a gas powered motor washer and dryer invention of mine and Laundry Mat until I devise a better system also forgot to mention water heating will be done by gas water heater
    Last edited: Dec 21, 2016
  7. Frozen2death

    Frozen2death Monkey

    First thank you for your response

    I have considered using a diesel Onan in fact, the gal/hr put me off even though you generate more energy per fuel consumed it seemed like I would be wasting power unless of course I could harness all of it into my battery bank within a few hours.

    My holding tank will be inside a extra room inside the house I am building.

    I'm not sure if I fully understand (OpSec Rules around here)
  8. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    OpSec is a Personal thing... "Operational Security". You only reveal limited Personal information in open forums like this... You just do NOT know who might read what you write.... Because of where I live, I. Am a bit more free, with my info, because I rarely leave here, and it isn't cheap, to fly or Navigate here... No Roads IN OR OUT...
  9. Frozen2death

    Frozen2death Monkey

    Well thank you for clearing that up, I think as long as address and my ssn is kept safe i should be safe and if not with my new 1911 I feel ok. :D
  10. Frozen2death

    Frozen2death Monkey

    Yeah haha I wish I could do trimming at my current house but with a 75 gallon electric hot water heater, electric heaters, electric wash/dryer, and electric appliances that's not happening, now my new house will be running about 600-800kwh from my calculations which I very much exaggerated for crazy amount of use, which is based off what I will be using and the max draw/startup also what I will limit myself to, I could afford to run a 5k generator 24/7 but I do not want to afford that, lol.
    I'm looking the most effective and efficient way to charge 500ah battery bank that's in 24 volt config. Possibly using a 3000 what gene to do it / power the house, simply put I set my limit on what my power consumption will be and will not go over it and if I do the culprits go away.

    Back to original thought here let's pretend I can manage to use 200Amp hours in a 24 hour period bringing my bank to 50%, and I want to charge it back is it better to run the generator to the house and charge bank and then switch only to bank till drained, or charge bank with generator while running from bank.

    I am very flexible on setup and the best way to do it that's why I'm here, but I do understand I need to manage my electricity consumption, it's impossible for me to give you or even myself the energy consumption that I'm truly expecting considering that everything that I will be putting in this new house will be new and different and built/works for offgrid rather than what I currently have. But I cannot just build the house and move into it with my family without having a power system setup.
  11. Frozen2death

    Frozen2death Monkey

    Also no harbor freight in my state. Which sucks:(
  12. Frozen2death

    Frozen2death Monkey

    So thinking to myself if 3000 watts ac is only going to allow me 27amps ac watts÷volts=amps. So let's say for loss of efficiency 20amps. 20 amps charging 500ah battery bank. Would charge to full in 25 hours assuming you could charge without slowdown the last 10 percent.

    So I answered myself I guess lol, 3000watt is not enough to power a bank if my current draw is say more then 800watts/hour. I could run my small gene 16 hours for my house and slow charge have enough bank power to run 8 hours at bed time. So if I move up to 10k generator I could charge the bank in full at 90 amps in 5.5 hours 10000÷110=90 then 500ah÷90amps per hour charge=5.5. Give or take some time/amps.

    So my brain hurts now, going to go locate my single malt scotch.
  13. Altoidfishfins

    Altoidfishfins Monkey+++ Site Supporter+

    Just my [2c]. If I were going to be using a genset that much, I'd listen to BT post and seriously consider a diesel, even a small one. They make 'em in 5 kw. Considering where you live you need reliability, fuel efficiency and long running time.

    I use a cheapo gasoline screamer but sunshine on solar panels is almost guaranteed in the Mohave desert. So use is occasional.
  14. oil pan 4

    oil pan 4 Monkey+++

    If you want the batteries to last use less than half the name plate amp hours between charges.
    Also if you want the batteries to last properly charging them is a must, they will need to be float charged for at least a few hours just about every day.
  15. arleigh

    arleigh Goophy monkey

    I run on both wind and solar and grid and diesel gen if necessary.
    If the gen is running I'm charging the battery bank as well.
    Primarily I am on the battery bank,
    Other things are contributors.
    Solar during the sumer is good, but not during the winter,
    wind is good all year round. and runs at night as well.
    If I had the $ I would get thermal charging panels as well and attach them to the wood stove, and run their cooling from the out side. and rout that residue air to feed the stove air. and multiply the heat.
    i recommend designing your home with more than you currently anticipate,in every way. collect books on alternative energy and learn from the pros/
    One thing I've learned through all my years is that every contribution IS a contribution large or small. and down the line they pay off in other ways as well if you've done' your planning right . ( bigger than expected).
    If I had the $ and plan to build a home , the foundation though it were made for a 2 story, a single story is done first .
    If I am planning a shop the foundation and pad would be made for a structure twice its initial size, so there is room for growth.
    Planning solar and battery banks and other needs in the same fashion.
    Pulling new wire replacing small conduit and relevant things is costly , but if from the beginning you plan big ,and build small expecting to grow naturally hopefully in the end your capacity can be met.
    When I built my shop trailer I didn't consider future growth . I should have started with 3 axils not 2 .
    ghrit likes this.
  16. Frozen2death

    Frozen2death Monkey

    Thanks everyone for your replies, I think BT is right about a 5kw diesel gene, enough to power house and charge my bank. Also I surely will build my power bigger then I need as arleigh suggest also thermal charging panels is somthing I should look into it never even considered that.

    Also I talked to a retired lineman today and I was worng about my calculations 3000watt 120v is 25amps ac but when you switch to lower volt dc the amps are higher. So 3000watt ac at 120v which is 25 amps is actually 138 amps at 24v dc. So since I probably want to charge somewhere between 20-40amps dc my Gene will be using 600-1000 watts ac and 4-8amps ac to make 20-40 amp dc at 24v. So I'm thinking of a 3-5k diesel genset would be more power then I would know what to do with but it does give me room to grow.
    Last edited by a moderator: Dec 22, 2016
  17. ghrit

    ghrit Bad company Administrator Founding Member

    I think you'll find 5kw is plenty, but not overly so in average household use. If your load study indicates that you will need less, go with it, cautiously. I would also consider two smaller units that could be paralleled; for the sake of argument, say a pair of 3kw machines. (Saying that, I have yet to see an 1800 rpm diesel that small.) Twin units would provide lots of flexibility as well as redundancy.
  18. Frozen2death

    Frozen2death Monkey

    I am setting up some autonomy to my system so whatever gene I get will have to be able to auto start or I atleast where I can engineer a start function into it. I have found some old old low rpm under 5kw diesel generators and a few newer ones. But the new ones are very pricy even more then the larger diesel but great fuel economy. Here is a old one i found for instance.
    Homelite 1800 RPM Generator Model G-3600-1
  19. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    If you can score an Onan MDJB/E (6Kw Twin Cyl) and an MDJA (3Kw Single Cyl) and put them in the same Powerhouse, with your Battery/Inverter Setup, you will have the best of BOTH Worlds... Big and Small.... The MDJA will run ALL Day on a couple of Gallons of Diesel, @2.5 Kw, and the MDJB/E is big enough to power a whole Outfit in the Alaskan Bush.... The ALSO have MANY of their Parts, and Filters, that are interchangeable, and in common. Should you need more Power than that, you can look for the MDJC/F (12Kw 4 Cyl) version.... These are ALL Liquid Cooled, which allows for Heat Exchangers, on the Cooling System, that will allow the Cooling System BTUs to be used for other purposes, like heating the House, an Outbuilding, or PreHeating Domestic Hot Water... Onan also made Air Cooled versions of each of the above units. (DJA, DJB/E, DJC/F) which also share many common Parts and Maintenance Items, as the rest of the J Series Onans. Onan also made Gasoline/Propane/Natural Gas versions of each of these Generator Designs. (JA, JB/E, JC/F) which also share many common Parts and Maintenance Items, as the rest of the J Series Onans. All the Manuals are available still and most of the Internal Parts are still around if you look a bit. These are ALL 1800 Rpm Gensets, and if you do the required Routine Maintenance , will still be running when your Grandkids, are living and running the place.
  20. ghrit

    ghrit Bad company Administrator Founding Member

    With a two unit setup, I'd be inclined to put them in separate houses. That way, should you be so unlucky as to have a fire in one powerhouse, the other might get by unscathed. But that's just me.
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