Off grid well water pumping system solar panel powered

JuliannJuliann Registered Users Posts: 2
Hi everyone,
I have been thinking to install an irrigation drip system for our strawberry beds. But then I thought why not do this as my next project and build a 12v solar power pumping system from our well. This should help me understand solar power and try to go as self sustainable as possible.😁😁
So my plan is to pump water from the well in a tank in the middle of the day when the sun is up and the batteries are fully charged and then pump from the tank 30 minutes early morning and 30 minutes late evening every day to the dripping system as I normally water my beds.
I thought this is a good idea as I don't have to use both pumps( or a bigger pump) at the same time so I don't need a bigger battery bank.
So the pumps are
•ECO-WORTHY submersible deep well pump .rated at 12v DC/4 amps
• SEAFLO pressure pump 42 series .rated at 12v DC /8amps

So my questions are:
1. How do I work out the size of the battery bank I need to use the submersible pump twice a day for 30min so 1 hour in total and to be enough atleast 2 days without sun?
2. How do I work out the corect size of cable i need?
3. Are 2× 100w/ 5.5A solar panels and a 15amp charge controler enough for what i wanna do?

Ps: ooo I forgot to mention that I am thinking to use lead acid battery as they are a bit cheaper 😊

Thank you so much in advance for your help and replays.

Have a good day.


  • EstragonEstragon Registered Users Posts: 4,484 ✭✭✭✭✭
    Can you elevate the tank above the beds? If so, you could use a bigger tank to last a couple of cloudy days instead of batteries, and eliminate the second pump. A bigger tank and gravity will likely be cheaper and more reliable in the long run.

    Running the pressure pump, assuming it takes 8a and runs for an hour, would use 8ah/day so 16ah for 2 days. A smallish 12v powersports battery around 50ah might work. I have what I think is a similar pump on my boat, and it seems to use power in surges though, so a bigger battery might be needed to handle. A pair of 225ah 6v golf cart batteries handles it on my boat.

    Wire size depends on current and distance. You could use a voltage drop calculator like the one at with you distances to get a reasonable size.
    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
  • JuliannJuliann Registered Users Posts: 2
    Thanks a lot for the replay and advice. There was a time when i considered gravity feed system but the distance between the beds and the well is about 20m aslo i asume the tank it po be placed high which I prefer not to do.

    The thing Im most confused is the watts,volts amps.. like the batterys are in amph(i know it means amount oh amps can supply in one hour) but then the panels are in wattsand tben on top of it the loads(in my case though the water pump has amp).
    But now it start to make a bit of more sense as u put it like the pump will use 8Ah( so then the amount of amps printed on the label will the Ah drained from the battery) 😁😁😅
  • BB.BB. Super Moderators, Administrators Posts: 31,336 admin
    Amps is a rate... Amp*Time (Hours) is the amount

    Roughly, a 32 AH battery discharging at 8 amps will last about 4 hours (of course, should not take it below ~50% capacity for longer battery cycle life).

    Yes, you can use Amps and Amp*Hours for figuring how much you take from the battery bank... It is assuming that all is at 12 volts (or 24 or 48 volts).

    However, when you start mixing voltages (12 VDC and 120 VAC)--It is better to work with Watts and Watt*Hours... Those are "complete units":

    Amps * Volts = Watts
    Amps * Hours * Volts = Watt*Hours
    Watts * Hours = Watt*Hours

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Registered Users Posts: 4,484 ✭✭✭✭✭
    At the risk of adding to the confusion on amps and amp-hours... the amps on the pump label may be an average rate of consumption over some period of time. This rate works for estimating the daily drain on the battery, but pumps in particular can have brief high loads to start.

    The pump on my boat appears to start and stop about twice per second (maybe using a piston sort of mechanism?), so my guess is it draws (say) 24a for 150ms twice per second, averaging out to 8a over the second. On the boat, this makes the lights dim at the same rate as the surging, about twice per second. Aside from being a little annoying, it otherwise works okay with a [email protected] battery. I don't know how a much smaller battery would handle the surging.
    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
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