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Summer cabin off-grid design stage

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  • SolarIslander
    replied
    You might consider a more suitable pump like the ones designed for solar by Dankoff. They have a wide range of "slow pumps" which are easy to start on PV along (facilitated by a current booster) or can be run off battery power or even 120VAC. These are positive displacement vane type pumps with highly efficient permanent magnet motors. We've used a 24 V version for years on a pair of 12 V 50 W panels direct wired to the current booster. Starts every day in the morning and pumps all day at about the rate of 1/2 a garden hose, pumping up 150 feet and over 600 feet to our tank. Very durable, well engineered, replacement parts widely available at reasonable cost too. You do need an inlet filter though, we change about once a year.

    Leave a comment:


  • Mike90250
    replied
    8 golf cart batteries 6v 200ah wired in series = 48V 200ah Each battery is about 70# Use a dolly to roll them around. Interconnect cables, SS bolts for the cables, fuses...

    1000 w of pv @ 48V = 20A so that's all the MPPT controller you need. Matches a 200ah bank perfectly (well, maybe a bit under, 230w x 4 = 920 x .8 =736 watts excepted harvest..
    Bring 2 more panels if you can, wire 3S2P

    How do the batteries stay charged in winter ?

    Do you need replacement distilled water for them ?

    How often does that big 1/2hp pump run ? Shift as many loads to daytime as you can

    Leave a comment:


  • Tyson1978
    replied
    Thanks for replies.

    I have abandoned the small battery idea. Everything brought to the cabin must be brought by boat and I do not want to bring something that I will have to haul out the next season marked NFG.

    I have 250W of lighting, 144 W for a propane on demand hot water heater (vent fan and ignition), and a 1/2 HP water pump for a total of 767 Watts. I would like a little room for expansion (maybe a small fridge in the future) so I thought a 1000 W load would be a good target. Which would be inverter load, but would be matched by 4 x 230 watt panels.

    Suneagle has made me realize that I will require 400 Ah battery. Since everything has to be brought in by boat and carried up to the cabin, I think I can eliminate a 12 or 24V 400 Ah battery, as there is not enough beer power in the world to move something like that.

    The cabin is only accessible from late spring to early Fall so solar hours for most of the time the cabin is used (June, July, August) would be 12+/day.


    Leave a comment:


  • Mike90250
    replied
    > these batteries (12V 5.8Ah) are a terrible choice for a solar application, and it would be a waste of time (and money) install them.
    Yes. they are tiny little batteries and to build sufficient capacity, would be a wiring nightmare

    > So, is the best option to use 6V 200+ Ah batteries wired in series to produce 24Vdc? If not, what would be the optimum battery type and configuration for a 1000W system?

    When you say 1,000w system, are you speaking of PV or inverter watts ?

    What are your required loads you are running ? That sets inverter size, and your battery capacity and your solar hours and replacement watts set your PV array

    Leave a comment:


  • citabria
    replied
    Just a note that online there are solar suppliers that have pre-sized solar kits complete with batteries etc., depending on your power needs. IMO it is worth googling to look at those options.

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  • SunEagle
    replied
    Originally posted by Tyson1978 View Post
    Thanks for your reply Mike,

    I have since done some very informative reading on this website (great info on here btw).

    From what I gather, these batteries (12V 5.8Ah) are a terrible choice for a solar application, and it would be a waste of time (and money) install them. The reason I have gathered from Mike, and other knowledgeable posters on here is running in parallel will cause a NFG state within months. due to lack of time for each bank to reach equilibrium. So my only option would be to have a single bank of 4 batteries at 48V, for a total of 23 Ah....

    Can I get confirmation that these batteries will not work for a solar application?

    I am leaning towards a 1000W system with a 24 VDC battery bank. Sunking's battery vs inverter sizing posts were a good wake up slap for me that I need my panel wattage matched to my inverter wattage. Since it is only feasible to mount 4 of my 230W panels that dictates my max inverter size to 1000W.

    So, is the best option to use 6V 200+ Ah batteries wired in series to produce 24Vdc? If not, what would be the optimum battery type and configuration for a 1000W system?

    Thanks in advance,
    Tyson
    A quick rule of thumb foro a balanced system is to use C/10 charge rate for your batteries where C = Ah rating.

    So for a 200Ah 24v battery you need about 20 amps. A simple formula to determine the panel wattage needed would be to multiply the required charging amps by the battery voltage or in your case 20amps x 24v = 480watts. From there you can fine tune the panel wattage based on your location and amount of useful sunlight that can be used to generate charging amps.

    For 1000w a 24v battery would need to be around 400Ah (1000w / 24v = 41.6amp x 10hr = 416Ah). The formula is not perfect but it gets you in the ball park.


    Leave a comment:


  • Tyson1978
    replied
    Thanks for your reply Mike,

    I have since done some very informative reading on this website (great info on here btw).

    From what I gather, these batteries (12V 5.8Ah) are a terrible choice for a solar application, and it would be a waste of time (and money) install them. The reason I have gathered from Mike, and other knowledgeable posters on here is running in parallel will cause a NFG state within months. due to lack of time for each bank to reach equilibrium. So my only option would be to have a single bank of 4 batteries at 48V.

    Can I get confirmation that these batteries will not work for a solar application?

    I am leaning towards a 1000W system with a 24 VDC battery bank. Sunking's battery vs inverter sizing posts were a good wake up slap for me that I need my panel wattage matched to my inverter wattage. Since it is only feasible to mount 4 of my 230W panels that dictates my max inverter size to 1000W.

    So, is the best option to use 6V 200+ Ah batteries wired in series to produce 24Vdc? If not, what would be the optimum battery type and configuration for a 1000W system?

    Thanks in advance,
    Tyson
    Last edited by Tyson1978; 02-22-2019, 01:37 PM.

    Leave a comment:


  • Mike90250
    replied
    In stand-by float use, batteries wired in parallel have time to reach equilibrium. In daily cycle service, they will drift apart in capacity and start failing in domino fashion in a couple weeks/months. If only weekend use, where they have a week to stabilize between cycles, you might get away with it for a year.

    Leave a comment:


  • Tyson1978
    started a topic Summer cabin off-grid design stage

    Summer cabin off-grid design stage

    Good Day Folks.

    This spring I will be installing a solar system in my remote cabin in Northwestern Ontario Canada (about 1300 kWh/kW/yr). I have an electrical/electronics background but most of my experience is unrelated (but transferrable). I have done a lot of reading on designing an off grid system. But due to circumstances my design process differs and this is making it hard for me to find the information to figure out some key things.

    Most system designs are based on the question what will the load be? In my case there is no electrical existing (all propane lights and fridge and stove) and everything will be added new. Also, I have access to some of the parts required for the system free of charge and plan to use them. I think this may dictate my maximum load I can output.

    Here is what I have so far:

    Batteries:
    My work replaced a 10KVA UPS system that had the inverter unit fail on it. Its battery banks consisted of 48 12V batteries (HR 1234W) These are spec'd at 34 watts, and I calculated from the data sheet for the battery that they will put out 5.8 Ah each. Other specs for individual batteries:
    I(short circuit) 349A
    I(maximum charge) 3.4A
    I(max discharge) 130A (5 secs)

    Yes I think this is overkill for my 2 season cabin which only is used on the weekends and a few week long trips every summer. But they were free, and I have no other use for them.

    Question1: what voltage configuration should I wire my batteries in? All my reading has pointed to the benefits of wiring up these batteries in a 48V x 4 bank configuration, which I calculate at 17.4 Ah per bank to a total of 69.6 Ah. This seems to limit the choices in charge controllers and inverters.

    Solar panels:
    At my residence I have a grid feed 10KW PV system. I have spare panels which I would like to use. My panels are Q-Cells QC-c05 230W with the following spec.

    Nom Power : 230W
    I(short circuit) - 8.3A
    V(open Circuit) - 36.6V
    I(at max power) - 7.75
    V(at max Power) - 29.65V

    I plan on bringing 4 of these units up to the cabin.

    Question: how should these arrays be set up, 2 arrays of 2 panels each? Without knowing the load is it possible to tell how many panels I should be using?

    Charge controller:

    I am trying to size the controller, it seems I am not sure how to go about this. I think I need to figure out my battery bank voltage setup and how my solar array will be wired before I know what current rating I should have on a MPPT charge controller? Is that correct?

    Inverter:
    Again, without knowing the total load it is hard to size the Inverter. I also think that I need to know what the battery bank voltage is before I can select one. Based on the system described can I calculate the maximum Wattage unit I should install? I know this is backwards from how it is usually done but I was hoping we could think this through.

    Load:

    Currently I plan on installing about 250W of LED lighting.
    L.P. on demand hot water heater rated 1.2A at 120V = 144 W
    0.5 HP Electric water pump - currently my father powers this pump with a generator. It is located at the cabin(no winter access) and I don't know the specifications for it. It may stay Generator only, but would be interested in putting it on the Solar system. It likely only gets about an hour of use per day.

    Thanks in advance for any insight you choose to share:
    Tyson
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