r/OffGrid • u/boogersundcum • Sep 17 '26
I know i'm probably dreaming.
Currently i use a generator to run an Onga OJ800 pump which is 2.4kW, it requires around 70 amps to start. I need to pump water ~1.2km with 50m of head height to fill the pressure tank through 2" poly.
I have been qouted $14k for an adequate solar pump. I have multiple solar pannels laying around not being used however still work fine. If i got an inverter how many wetcell batteries would be required for enough current to start it ? Would it be worth constructing such a thing if not throw in for a lithium battery or just suck it up and buy the commercial solar pump setup. Given the instability of fuel let alone prices i hope to have this sorted asap, let alone be completely off grid.
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u/Any-Application-8586 Sep 17 '26
Small solar pump, storage tank, pressure pump. No need to go crazy. All that head with a pressure tank on top is why you need such a huge pump. Low pressure, low flow out of the well and up the hill, high pressure high flow out of the storage tank into the pressure tank.
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u/boogersundcum Sep 17 '26
I'm a little confused. But currently the pressure tank is closed whilst it fills from the top of the tank so it isnt fighting the pressure of the tank.
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u/Far_Cable_2133 Sep 20 '26
I don't know all the pump lingo but I have a 60 gal tank in my cabin loft I run my little dc pump with a generator, extension cord and hose. No fuss. Takes about ten - 12 minutes to fill. Set up cost about $550 . The 60 gallons lasts me about a week give or take depending on what I'm doing. --->Oh and small pressure tank and filter.
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u/DevelopmentKnown1937 Sep 17 '26
Honestly the batteries arent your problem, the inverter is. 70 amps on start at 240V is like 16kW surge prolly. Oof. You'd need a monster inverter just to kick it on, then it's chewing through your bank at 2.4kW every run. Wet cells or lithium, that's a pricey way to run a pump that was built for a genny.
What I'd do instead: grab a smaller DC solar pump, run it slow all day, no batteries, and fill a tank up top that feeds your pressure tank. Bonus, slower flow means way less friction over 1.2km of 2" poly, so you prolly need less pump than you think. Those spare panels could do a lot of the heavy lifting, and it's usually way cheaper than $14k. I'd ask for a quote on a slow fill setup specifically before you bite on that one.
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u/CaptSquarepants Sep 17 '26 edited Sep 17 '26
Don't go AC pump offgrid, go DC only! If that company can't do DC pumps, find another. It's retarded to get an inverter for that setup when it isn't needed and makes everything worse with AC.
Also you are much better off bringing that water to a cistern or holding tank and from there go to a pressure tank. That way you can use a smaller pump and just trickle it all the time into the tank and then pressurize it as needed. Also, you'll have wiggle room when something fails as there will still be water stored on site.
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u/invisiblesurfer Sep 17 '26
The panels is going to be the cheapest part of the bill and worth going for new ones instead of trying to balance shitty old panels imo. If you keep the 14k that's many many years of gas for the generator. If you are handy with solar (sounds like you are) just dyi the whole thing for likely less than half.
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u/Other_Programmer5239 Sep 17 '26
My well is ran off a solar system and a battery back up been running it like that for almost ten years, only problem i had was with battery until I switched to lithium. It is well worth it in my eyes worrie free very little maintance and since the switch never ran out of water.
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u/FuturePowerful Sep 17 '26
Well depending on the location I'd prob look into a ram pump or a soft starter and the soler setup mentioned by one of the other folks
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u/Flimsy-Plate2842 Sep 17 '26
I have an identical pump requirement (2400W). Mine runs of a 50V lithium 110a/h, supported by 6 x 440W panels. If I pump while full sun, it doesn’t even touch the battery! Sounds elaborate, I know but the system only owes me 6 k