Water Pressure Pump

rp3703rp3703 Registered Users Posts: 61 ✭✭

I looked through the forum and could not find anything relating to my situation. Feel free to direct me if there is one I missed. I have a lake cabin that uses a gas trash pump to pump water to an elevated water tank that feeds a shower, sink and kitchen sink using gravity alone. As you can guess water pressure is next to nothing. I am wanting to add a water treatment system so we can drink the water from that same tank. This treatment system requires at least 40 PSI to push water through it’s various filters. As of yet, we do not have a solar power system yet but I am currently working out my power requirements. One of which is powering a pump that will add water pressure. Correct me if I’m wrong but I am thinking all I need is a pump similar to what RV’s use running off 12V, hooked in line that only turns on when it detects a draw. I need to determine what equipment I need and then how much power will be required to run it. 



  • mvasmvas Registered Users Posts: 298 ✭✭✭
    edited February 9 #2
    Start with ->  How many gallons of drinking water per day will you need?
    Then select the water pump and storage tank to satisfy your water requirement.
    Then select the size of the solar panels, battery & charge controller per the ( Watts x On-Time ) of the electric pump.  

    Is it possible to store enough pressurized drinking water to eliminate the expensive batteries?
    A small pressure tank will help keep the water pump cycling to a minimum.
  • EstragonEstragon Registered Users Posts: 1,416 ✭✭✭✭
    +1 on the pressure tank if possible. The 12v pump on my boat makes quite a racket. Someone getting a drink in the middle of the night would wake the dead.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mike95490mike95490 Solar Expert Posts: 7,249 ✭✭✭✭

    Gravity is your friend.  If you have elevation, pump to the high tank, and let gravity do the work when the pump is off.  I've got several thousand feet to get to the high tanks, but now have 70PSI (on the high side) while there is any water in the tank, and I manage the pump running only on sunny days
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • dennis461dennis461 Registered Users Posts: 81 ✭✭
    If the goal is to provide drinking water only, then GPM is not a big issue, you simply need the pressure for pushing through filters.  A 12VDC positive displacement pump should work for you. Search for ,12V DC MARINE/UTILITY WATER PUMP.  I think you will find some cheap ones (meaning buy two) with 50PSI.  Perhaps two separate holding tanks, then you don't need a pump on demand system.  Also consider that 50PSI (or your required 40PSI) will be on the filter inlet, filter outlet pressure will be lower, right?

    Does the trash pump proviede 40PSI? Tap into that pump outlet for water filters, and separate pipeline to the clean water tank.
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • rp3703rp3703 Registered Users Posts: 61 ✭✭
    While my primary concern is the water treatment system, I would actually like to at least add pressure to the shower if not all the fixtures. I'm just trying to figure out what is required. I've put in a request with a pump company to size a pump and tank. Once I get that info, I should be able to move forward. The gas powered trash pump is only turned on to fill the elevated tank. It would be kind of impractical to use it for the water filter unless we were filling water bottles. Good idea though.
  • mike95490mike95490 Solar Expert Posts: 7,249 ✭✭✭✭
    Generally, you want to limit "Starting Cycles" on a pump.  using a larger pressure tank (2x 50 gallon vs a 12gal) gives fewer starts but longer run times to pressurize the system.  You have to calculate the flow rate (pressure bleed down) for the water filter to come up with a reasonable size pump & pressure tank.  Both should be sized together as a whole, to work better together.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • ramlouiramloui Solar Expert Posts: 102 ✭✭

    Hello RP,

    I am in the same situation at my cabin and my gravity tank (about 15 ft elevation) feeds into a 12V rv pump to a 20 gallon pressure tank, through a 1 micron filter and on to the cabin. The pump, pressure tank and filter are installed in the shed. This setup works very well for me. Plenty of pressure at the faucets and shower. It is not drinking quality though. Pressure also allows me to meet the minimum required by my on-demand propane water heater.

    My system needs to be winterized when I close the cabin in the fall. To do that I have installed a Tee, valve and pipe on the suction end of the rv pump so that I can stick a jug of RV antifreeze and push that all the way through the cabin piping to prevent damage to the pipes in freezing weather. In the spring, I just gravity drain all the piping, fill the gravity tank with lake water, rinse a little and voilà!

    Good luck!

    Louis R.

    Off-grid cabin in northern Quebec: 6 x 250 W Conergy panels, FM80, 4 x 6V CR430 in series (24V nominal), Magnum MS4024-PAE
  • 706jim706jim Solar Expert Posts: 154 ✭✭

    Maybe my experience will help. For several years, I ran a Jabsco 12 volt diaphragm pump to pressurize water in my island cabin. It fed a kitchen sink faucet and a shower that was heated by a 5 gallon RV tank. I used a group 24 deep cycle battery and NO solar panels whatsoever. I could usually get about a month's use before charging the battery. Nominal water pressure from the Jabsco was 20 to 40psi. I'd suggest fitting a captive diaphragm pressure tank of about 2 gallons capacity to reduce pump cycling. The newer Shurflo pumps would probably work just as well as the Jabsco.

    You could pump water directly from the lake if the elevation is within 5 feet or so. Those little pumps push well, but don't lift water very far.

    Island cottage solar system with 1400 watts of panels, Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. My 22nd year.
  • rp3703rp3703 Registered Users Posts: 61 ✭✭

    So I’m looking to at one of those Shureflo 12 volt pressure pumps to pressurize the water to run a shower and a water filter. The pump I looked at states it will draw around 6 amps and the average deep cycle battery has 80 amp hours. So do I just divide the the draw of the motor by the number of amp hours the battery has to figure out how long one battery will run the pump or 13 hours per battery? Is there any more to this calculation?

  • BB.BB. Super Moderators Posts: 26,758 admin
    Yes... There is a lot more.

    Generally, to keep things simple, we give "approximatly accurate" answers to questions to keep things easy to understand. And from that point of view, your answer is correct.

    The details... Batteries are not ideal, and as you draw larger amounts of current from the battery bank, the apparent capacity drops.

    For example, here is a Trojan T-105 (6 volt, golf cart type flooded cell lead acid storage battery) various discharge rate capacities:

    • 5-Hr Rate185 AH
    • 10-Hr Rate 207 AH
    • 20-Hr Rate 225 AH
    • 100-Hr Rate 250 AH
    AGM, GEL, various Li Ion type batteries will have a "smaller spread" (more efficient, less capacity loss at high current draw, etc.).

    Your ~13 hour discharge rate puts you closer to the 10 Hour Capacity... Say a 10% loss of apparent capacity, you will have -1.3 hours less useful energy, and ~11.7 hours of discharge.

    And, for deep cycle batteries, we recommend that you only discharge to 50% of capacity--Or 5.85 hours of stored energy between recharging cycles.

    Flooded cell batteries lose (at 75F) around 25% of their capacity per month... So, over one months between chargers, you are now closer to 25% of usable capacity--So now ~2.9 hours of usable energy (monthly recharges).

    But, if you store a lead acid battery below ~75% state of charge, they begin to sulftate (fluffy gray lead sulfate becomes hard black sulfate crystals which are permanently lost to the discharge/recharge capacity of the battery).

    There is is the differences in apparent capacity at different battery temperatures. A hot battery has more apparent AH vs a cold battery (Rolls):

    And then there is battery aging... One battery mfg. (Concorde) says their battery end of life is when capacity falls to 80% of new... So, another derating for old vs new batteries.

    The long "answer" depends on details of your usage, battery chosen, environment, how you recharge, etc...

    The short answer is we use "rules of thumbs" to give "close enough" answers that will give you a reliable system that will meet your needs.

    Does this help?

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 844 ✭✭✭✭
    But figure that you don't want to draw your battery below perhaps 50%.  So 6.5 hours.   Regarding filters, best to do it slowly (ie, low pressure) and store the result in a large pressure tank.    High flow rates through small filters is inefficient.

    Consider using chlorine as part of your water treatment.
  • rp3703rp3703 Registered Users Posts: 61 ✭✭

    I posted that question a little prematurely. It’s looking like the kind of pump I may get(5 GPM) will draw more like 15A but with at most ten 10 minute showers per day, probably closer to 5, the pump would run for 1.5 hours each day for the showers alone. I plan to use a UV light water filter with a two stage cartridge filter which I think requires at least 30PSI to push the water through the filters and I would like to hook it up to it’s own spout. So I’m guessing to supply 10 people with drinking water will maybe run the pump for at most 2 hours a day. So that’s a total of 3.5 hours of use each day. Where I’m having trouble is figuring how much power will be used to charge everyone’s cell phone each night. After I get that figured out, the only other load on the system will be a few LED lights that should run for at most two hours at the end of each day. 

  • rp3703rp3703 Registered Users Posts: 61 ✭✭
    I should not have to worry too much about cold batteries since the system will only be used from June through August.
  • EstragonEstragon Registered Users Posts: 1,416 ✭✭✭✭
    If you can charge phones with 12v directly with a cigarette type plug, I'd guess 1 or 2 ah each. It could be a lot more if using a big inverter for the small load though.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • rp3703rp3703 Registered Users Posts: 61 ✭✭
    Wow, I never even thought of that. Would it be easier on the batteries if I used DC for everything? Would just installing USB outlets at a distance of 20'-40' from the batteries be an issue? Like I said, I'd need about 10-15 of them. Anybody know whether DC LEDs are any good?
  • rp3703rp3703 Registered Users Posts: 61 ✭✭
    So how do I use your 1-2 AH for each phone to figure my power needs? Do I multiply that by the max number of possible phones(15)? Is the 1-2 AH the total usage to charge the entire phone ?
  • mcgivormcgivor Registered Users Posts: 1,190 ✭✭✭✭
    edited March 24 #18
    rp3703 said:
    Wow, I never even thought of that. Would it be easier on the batteries if I used DC for everything? Would just installing USB outlets at a distance of 20'-40' from the batteries be an issue? Like I said, I'd need about 10-15 of them. Anybody know whether DC LEDs are any good?
    All LED lights are fundementaly DC, the ones that use AC will have a driver to rectify the AC to DC, so using an inverter simply to use LED's is not the best method, the inverter would most likely consume more than the lights themselves, assuming there are just a few. Your  phones will use 1Ah +/- each, the same rationale as the lights applies, cell phones are DC.

      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • BB.BB. Super Moderators Posts: 26,758 admin
    If you are keeping wire runs short--DC can work.

    However, if you have lots of wires going everywhere and longer distances (20-40 feet is getting towards longer distances), then I would get a nice little AC inverter. The MorningStar 300 Watt TSW 12 VDC inverter is pretty nice for the job. Plus has low power standby/remote on-off functions too.


    You can send 120 VAC at 300 Watts for hundreds of feet on a small gauge extension cord. 12 Volts, not so much:


    For example, 14 AWG (house wiring) sent 40 feet (one way run for above calculator) will have a 0.5 volt drop with only 2.5 Amps (roughly 29 Watts at load).

    I also like using an AC inverter... An off grid solar off grid 12 VDC Battery bank will see ~10.5 to 15.0+ volts (full load/voltage drop to EQ'ing battery bank)... A lot of "12 volt car adapters" may "have issues" with that wide of voltage range.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rp3703rp3703 Registered Users Posts: 61 ✭✭
    According to your calculator, the voltage drop at 40' for the same load running DC is .8. Is .3 difference that much of a difference? My concern is more with which method will draw the batteries down the quickest. If there is no difference or very little difference then yes, an inverter would be the best way to go. To me converting energy from DC to AC and then converting it back to DC, seems like it would be wasted effort but I'm no expert.
  • HorseflyHorsefly Registered Users Posts: 250 ✭✭✭
    As a general rule, an inverter will be about 85% efficient, meaning that you lose 15% in the conversion.

    For DC, the important number is the percentage drop, not just the voltage drop. You are using a lower voltage in the first place, so to get the same watts you need more current. More current means you lose more voltage due to wire resistance. Since the original voltage was small in the first place, the percentage drop is even bigger. 

    So if all you DC loads add up to a higher percentage drop than 15%, an inverter would be more efficient. 

    In my case, I'm going to have a few select DC loads in the house but most will be via the inverter. I will be using some leftover #6 wire  for the home runs to those loads to keep the losses low.

    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • BB.BB. Super Moderators Posts: 26,758 admin
    I am not sure what numbers specifically for 0.8 volt vs 0.3 volt drop... But the usual math for a battery in a car is:
    • 12.0 to 12.8 volts (good, charged battery)
    • 13.8 to 14.2 volts (nominally charging battery at ~75F)
    • 15.0 to 16.5 volts ("equalization voltage" for typical lead acid flooded cell battery)
    • 10.5 volts (dead battery at rest)
    • ~11.5 volts (minimum battery voltage for 50% discharged battery under load at ~75F)
    • ~10.5 volts (typical cutoff voltage for AC inverter input--To protect the AC inverter and loads, not to "save" the battery from being taken "dead" which is a bad thing for most rechargeable battery chemistries).
    So--Now you have to look at your DC loads... Most car adapters seem to "expect" 12.0 (perhaps 11.5) volts to ~14.5 volts. Above 15 volts, we have had reports of some failures (cheap adapters and "good quality" laptop computer adapters too).

    Most DC devices (electronics, motors) are designed for a 5% +/- (0.6 volt) regulated output. An off grid battery bank is something like:
    • 16.0v - 10.5v = 5.5 volt volt spread
    • 10.5v + 0.5*5.5v spread = 13.25 volt nominal +/- 2.75 volts or +/- 21%
    That wide range of "unregulated" voltage is not "ideal" for many 12 VDC loads. Lights will be dim or bright, brushed motors will vary in RPM, electronics will need "better regulators", etc.

    Also, if you assume a 11.5 volt minimum battery voltage 10.5 volts minimum load voltage. That gives you 1.0 volt headroom for wiring and fuse/circuit breaker voltage drops. And your load has surges--Say 2x current for starting load, then you only have ~0.5 volt "headroom" for your loads.

    The difference between 0.8 volt drop and 0.3 volt drop at the end of the wire run to the load may mean you have dimming lights, DC radio dropout, etc. when loads are turned on. For things that are charging batteries (cell phones, laptop computers with batteries, etc.), the "dropouts" are not usually a problem.

    In the end, assuming that your AC inverter is ~85% efficient, and that a 120 VAC to 5 VDC USB charger is about as efficient as a 12 VDC to 5 VDC USB charger--You have ~15% losses to run the inverter. 1/0.85=1.18 or your Solar panels+battery bank needs to be 18% larger to support the AC inverter--That is not too expensive these days.

    Also, secondary issues become "easier" to manage with 120 VAC circuits. A 300 Watt AC inverter is ~2.5 amps output . If you have 300 Watts of 10.5 amp (minimum battery voltage load input), that is ~28.6 amps. You need much heavier wiring for 12 VDC circuits (with 0.5 volt drop allowed vs ~12 volt drop for a 120 VAC circuit).

    Plus you now need fuses/breakers for each (as an example) 14 AWG + wire that leaves the battery bus to its 40' wire run. You have a battery bank that can put 100+ amps into a dead short. The 300 Watt inverter, only ~5 amps into a dead short before it shuts down. No fuses/breakers needed for "nominal 14 AWG or even 18 AWG wiring (recommend keeping with 14 AWG wiring for 15 amp rated circuits).

    Plus, if you have an AC genset for backup/heavy loads (tools, vacuum, etc.), you can use the same AC wiring for those loads with the AC genset (and a larger AC inverter if you ever upgrade your off grid system).

    For "standard" DC outlets--you are left with cigarette lighter receptacles (the car 12 VDC standard). Big, bulky, (some of mine fall out from spring contact pressure issues), and limited to 10 amps/120 watts maximum. A 120 VAC power strip typically supports 6 outlets, is much smaller/more compact/more reliable. And a kid cannot drop a penny in your 12 volt receptacle and blow the fuse/wiring.

    That is why I suggest an AC inverter for any power that needs to be sent much more than a few feet from the battery bank, or needs to be much more than 10 amps / 120 Watts.

    Figure out the costs and design issues for your needs--People have done fine with 12 VDC--Converter to Anderson Power Pole connectors for your 12 VDC (common connectors for HAM Radio 12 VDC installations--And there are 12 VDC "power strips" and such available too). Your needs, your installation. Just my two cents worth of opinion.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Registered Users Posts: 1,416 ✭✭✭✭

    I was thinking you might be able to charge phones at a common charging point close to the battery, not charging 15 of them at various points up to 40' away. As Bill points out, wiring and managing that gets unwieldy.

    The morningstar inverter would probably be a better choice for your use. I use one for smaller overnight loads, and it is quite efficient for that. What you don't want to do is run a bigger (eg 2000w) inverter all the time just charging phones, as you can end up with ~1kw (80ah) of daily load just to keep the inverter lit. The actual charging load for 15 phones might be 20ah or so.

    I get all the wall warts put on a power bar which gets turned off at night.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • rp3703rp3703 Registered Users Posts: 61 ✭✭

    Thanks for the in depth explanations. Sorry for taking this post down that rabbit hole but thanks for pulling me out. Inverter it is.

    I realize I should look this up myself but I figured since it sounds like I have a panel of experts here, I’d like to get as many opinions as I can on how best to fulfill my power requirements. So I have the 15 amp water pump that will run up to 3.5 hours a day(hopefully less with the addition of a pressure tank), the up to 15-1AH cellphones charging each night and I’m figuring 8-10 lights using cheap 9 watt LED bulbs that would run at most 1-2 hours each night. How do I go about figuring how many batteries I need and how many panels I will need to keep these batteries charged sufficiently?

  • BB.BB. Super Moderators Posts: 26,758 admin
    RP, this is your thread--It "goes" where you want to to go. As always, have fun here!

    To design your system, you need to understand your loads. And pick as energy efficient loads as you can for your needs.

    Note that sometimes, picking your loads also has other issues to think about. An inexpensive DC RV 12 (or 24) volt water pump is usually a "brushed" or "universal AC/DC" motor (like typical electric drill or vacuum cleaner motor). Their drawback is that they use carbon brushes on a commutator (so that the motor will run on DC power). The downsides (tend to be) are "relatively" short brush life (2,000 to 5,000 hours +/-) and electrical noise from "sparking brushes/communicator" (possible problem if AM radio, HAM radio).

    There are brushless pumps (both DC and AC) that will run longer. For running "cabin/RV" water, you are only running the pump minutes to an hour per day--That means something like a 2,000+ day life (5+ years). If you where pumping for irrigation water (10 hours a day, 200 day life) and/or had deep well pump (pulling the pump for service every year)...

    The difference between a $200 nice quality DC RV pump and a $1,000-$2,000+ VFD (variable frequency AC drive) pump for an "off grid" friendly installation, or a large AC inverter+battery bank to drive a standard in well 120/240 VAC deep well pump which drives up the costs of your solar power system with a less expensive/longer life pump.

    You may have to do several paper designs (and costings) to figure out what works best for you.

    Energy budget wise:
    • Cell phone (guesses): 1.77 amps * 1.5 hours * 5 volts USB = 13.3 Watt*Hours per day (my Samsung S7 one full charge per day)
    • 15 cell phones * 13.3 WH per day * 1/0.80 typical charger eff = 249 WH per day
    • RV Pump: 15 amps (sounds high) * 3.5 Hours per day (sounds high) * 12 volts = 630 WH per day (that is typically >>1,000 Gallons of pumped water per day--Average home uses ~40-80 gallons per person per day)
    • 9 Watt lights * 10 bulbs * 2 hours per day = 180 WH per day
    Normally, we would divide the loads between AC and DC... DC loads do not have the 85% efficinecy of an AC inverter to deal with... But, for now, I am going to assume that all of your loads run from AC inverter just to keep the "math simple" in this post (and be on the conservative side).
    • 249wh + 630wh + 180wh = 1,059 Watt*Hours per day loads
    Battery bank design... This is a "small system" (1,000 WH or 1 kWH per day is a cabin size system with lights+small electronics+RV pump type system--very reasonable) and will run on a 12 volt battery bank. 2 days of storage (usually optimum price/performance point) and 50% maximum discharge (for longer battery life):
    • 1,059 WH per day * 1/0.85 inverter eff * 1/12 volt battery bank * 2 days storage * 1/0.50 max discharge = 415 AH @ 12 volt battery bank
    A good battery bank would be 2x 6 volt @ ~210 AH "golf cart batteries" in series * 2 parallel strings (4x batteries total) for a 12 volt @ 420 AH battery bank (cheap/rugged/forgiving batteries--Especially cheap).

    To charge the battery bank, to calculations. First based on battery bank "size" (larger battery banks, need more charging current). 5% to 13% rate of charge recommended. 5% can work for weekend/summer use. 10%+ recommended for full time off grid system (9+ months of the year).
    • 420 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 395 Watt array minimum
    • 420 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 791 Watt array nominal
    • 420 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,028 "cost effective" maximum array
    And then there is sizing the system on the amount of load and where it will be installed. I may have missed your your location, but guessing as near Nashville TN, fixed array:

    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 69° angle from vertical:
    (Optimal summer settings)
    Jan Feb Mar Apr May Jun
    Jul Aug Sep Oct Nov Dec
    June through August usage... >5 hours of sun per day... Will use 4.0 hours per sun to allow for some cloudy weather (reduce any genset usage):
    • 1,059 Watt*Hours per day * 1/0.52 end to end system eff * 1/4.0 hours per day = 509 Watt array minimum recommended
    So--Somewhere between a 509 and a 791 Watt array would seem to make sense (based on all of my above guesses).

    And, probably a MorningStar 300 Watt TSW AC inverter would work nicely (remote on off/sleep mode--Do not find often on small AC inverters):


    Should work nice if your loads are less than 300 Watts. It is always a push figuring out if you need to design for "worst case" loads (everything at once, vs typical loads, some lights, some cell phones, DC water pump)....

    Some numbers to start with....

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rp3703rp3703 Registered Users Posts: 61 ✭✭

    Wow, thanks Bill, for putting this together. I do live in Nashville but the system will be installed in Ontario Canada in a lake cottage near Sudbury. From what I could find, it says they get around 7 hours of sun each day from June through August so the 5 hour numbers you used should be safe.

    This is the pump I was looking at:


    It lists 12 amps max. I just rounded up to 15amps incase I find something else. 

    My figure of 3.5 hours a day came from 10 people taking a 10 min shower each day(1.5 Hrs-about) and the drinking water faucet being open for up to 2 Hrs each day. I know it was mentioned that adding a 2 gallon pressure tank would allow to pump to cycle on and off less but I don’t know how to figure how much that will be. As I stated in my first post, I still plan to use a gas powered pump water from the lake to an existing elevated water tank. The 12v RV pump will only be used to pressurize the water from the tank to a shower and a UV water treatment system for drinking. Now that I think about it, I need to figure the load from the UV light. Oops.

    Do you have any recommendations for brand of battery. Trojan seems to be the brand of choice, just wondering if there are any cheaper alternatives with similar performance.

    I would also like to shut the system off completely for the winter, would that just involve disconnecting the batteries, bringing them home, hook them to a charger all winter and then bring them back? I know there is more involved to maintain the FLA batteries which is a whole other subject, I’m just concerned with not messing up the panels or any other equipment.

  • BB.BB. Super Moderators Posts: 26,758 admin
    For Sudbury, the estimated hours of sun for a 30 degree tilt (weighted towards summer production) from horizontal is:
    MonthSolar Radiation
    ( kWh / m2 / day )

    Not 7 hours of sun, but 4 hours would seem to be a very safe estimate. Also--Panels must be shade free (at least, ideally, from 9am to 3pm)--Any shading (just one branch, overhead electrical line, vent stack/chimney will cut the array output by a lot (upwards of 1/2 or more is not uncommon).

    If you mount panels for over winter float charging--Do them near vertical mounted on wall/sort of high... The will be, more or less, self clearing except when the snow gets too deep. ~100 to 200 watts of panels and a simple PWM charger would work well to float the batteries during storage.

    I will let others discuss battery brands... Many times getting batteries local is a good idea (heavy, acid electrolyte, etc.). For your first batch, probably want to not spend a lot of money--Many people murder their first bank or two. Golf cart batteries at less than ~$100 each (Costco, Walmart, etc.) are not a bad deal. If they only last 3-5 years, you are still ahead. And if you kill your first bank, it stings less.

    Regarding storing of batteries... Disconnecting them for 3 months (after they are fully charged) and letting them cold soak, not bad (fully charged batteries will not freeze until under -70F--Cold batteries do not age very fast and can last for many years).

    Problem will be with flooded cell batteries, 9 months without service (even on a light float charge)--You run the risk of running the batteries dry (expose the plates to air/oxygen, and the battery is not long for this world). I just don't know if standard flooded cell golf cart batteries would go that long without servicing/checking electrolyte levels, etc. (you would need at least 4-8 amps of float charging from solar or utility power for that bank).

    Hauling 4 golf cart batteries back and forth to Canada may not be a favorite either. If you can find somebody to leave them with in Canada with a float charger (Battery Tender or Battery Minder or good quality small solar panels+charge controller) where somebody can check the water and charge once a month or so would be better.

    Trojan does make some newer off grid RE batteries:


    A few people here have said that they use much less water (the reports I saw were full time occupied, and in the desert southwest--Should use less water in Canada through a long winter on float).

    AGM batteries are a possibility--But they are much more expensive and a bit more temperamental (they do not like hard/over charging--The are sealed batteries and once you over charge and vent them, their life is limited). Also sealed/AGM batteries, you cannot check specific gravity with a hydrometer--The gold standard for determining battery state of charge and diagnosing problems. Not great for learning on a first bank, but pretty nice batteries in general.

    And there is always the question of security with unoccupied structures--Not spending too much money on stuff left over winter is usually not a bad idea.

    I will let others here talk about what is best from their experiences.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • westbranchwestbranch Solar Expert Posts: 4,822 ✭✭✭✭
    Ah ha..Sudbury.  I suggest you inquire with the Border  cops about bringing in materials like the pressure tank, pex pipe, pumps etc ... you may find it cheaper to source on this side of the 49th than getting them down south and having to pay our 12% GST ,  there is normally no DUTY applied due to NAFTA, applies to all stuff made IN Mx. USA and Canada... Sometimes they let you pass, others they want 2 pounds of flesh..  inflation.... had it both ways with solar stuff. :) :o
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • EstragonEstragon Registered Users Posts: 1,416 ✭✭✭✭
    HST in Ontario - it's 13%. You will (almost) certainly have to pay this at the border. On the other hand, you will certainly have to pay it buying stuff in Ontario. I have never had duty on any solar stuff I've imported - just GST or HST.

    Some things may be cheaper to bring with you. I've found controllers, inverters, panels, and racking cheaper and easier to find in the US. Batteries, pumps, pipe, etc. not so much. Might be worth finding out what's available in Sudbury and asking for some prices. Ontario had a pretty generous feed in tariff program until fairly recently, so there may be some good vendors there.

    If you can locate batteries somewhere that moderates temps you might be able to get away with leaving them fully charged over the winter. Most people with sailboats and houseboats at the NW Ontario marina I use leave batteries in boats over the winter with no charge source from Oct to May. In your case the problem would be the late spring. It starts getting pretty warm by late April. If the batteries got warm too, and sat through May, they would sulfate. If they were in a dug out, the ground would keep them cool, but in a cabin they would probably get too warm.

    Taking batteries home is the best option. 4 golf carts wouldn't be so bad to handle. If your needs expand and you have to move 4 L16s at ~140lbs each back and forth though...
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • rp3703rp3703 Registered Users Posts: 61 ✭✭
    The border is the least of my worries at this point. If I rub some dirt on everything, who's to say I don't bring all the equipment back and forth every year. Anyhow, I'm more concerned with making sure the system will work. I found with a local source for 270 watt Canadian Solar panels that I can buy without having to pay freight and there is a Trojan battery distributor 30 min out of town. I'm looking at using a Midnite Solar Kid for the charge controller. I need to do more research on advantages to series and parallel wiring of the batteries and panels though. Thanks again for all the help with this.
  • rp3703rp3703 Registered Users Posts: 61 ✭✭
    Bill, if you are out there. In line #19 of this thread you suggested I use "The MorningStar 300 Watt TSW 12 VDC inverter". I was wondering how you came up with 300 watt. If you feel 300 watt is more than enough for what I have listed above, then I'm fine sticking with that but if that is pushing it and with minimal cost difference, should I just up it to 600 watt? Would a 600 watt inverter work with a 12V 450 AH battery bank?
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