Livestock water well

SystemSystem Posts: 2,511 admin
I have a 24 volt submersibble pump for pumping water to a livestock tank. The pump is currently wired directly to two 24 volt solar panels. The system works fine all day long when the sunlight is adequate.

What I would like to do is hook up two 12 volt batteries (creating one 24 volt battery) inline so that I would get a few more hours of pumping after the sun goes down. I need the panels to charge the batteries and run the pump during the day and then have the batteries run the pump after the sun goes down. The batteries don't have to run the pump for the entire night.

Do I need a blocking diode between the batteries and the panels? Should the panels be hooked up in series or parallel? Will the system work the way I've described, or am I on the wrong track?

Comments

  • mike95490mike95490 Solar Expert Posts: 8,191 ✭✭✭✭✭
    Re: Livestock water well
    jjh266 wrote: »
    .... batteries and the panels? Should the panels be hooked up in series or parallel? Will the system work the way I've described, or am I on the wrong track?

    I'd call it the wrong track. You are now adding battery complexity to the mess.

    1) if you add batteries, you will need to add more PV to charge the batteries, right now, your current PV is busy running the pump.

    2) batteries will need a charge controller, with a load control, so the pump does not run the battery down flat.

    Just duplicate what you have, a pair of panels, and another pump. You gain redundancy.

    You could aim 1 array SE, and the other SW, and spread your pumping over a longer period instead of both pumps running full bore at noon, and drain the well.
    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 ,

  • BB.BB. Super Moderators, Administrators Posts: 28,768 admin
    Re: Livestock water well

    You will probably have to "do the math" and figure out how much water you are getting today, how much you need, and by season... Then price out the system changes/upgrades.

    I agree with Mike that adding batteries to the mix will add complexity and costs... Batteries will make the solar power about 3-4x more expensive (battery costs, battery replacements, maintenance, added controller/timer, needing to add solar panels because adding batteries will reduce your overall electrical efficiency from ~77% down towards ~52%).

    You might look at your pumping efficiency (can a more efficient pump get you more water with fewer panels/no batteries)? Can the well handle higher "noon" peak flow rates, or not? Have you looked at adding a linear current booster (here or here) to better match solar panel's output to the pump's input requirements? Would a larger water holding/storage tank help your situation or be needed if you just pumped more water when the "sun was shining"?

    Will adding more solar panels (or even possibly a tracker--though, probably would only suggest if your well cannot source more water at noon--spread solar energy farther out into the mornings/evenings).

    Regarding how to connect the solar panels--for any system with more than a few watts of solar panels, you will need a charge controller--probably an MPPT type controller (better controller, more power collected, better battery charging, more controller options). Panels and a blocking diode will not be "good enough".

    Also, regarding the size of the batteries... You really need to know how much electricity (amps, volts (or watts) and hours per day). The battery bank should be sized for about 3-6x your daily "battery" energy use (to ensure long battery life and some pumping on "dark days" -- if needed).

    In the end, you can create a very nice battery/solar power system for your water pumping--but the added expenses and complexity probably would guide you down the path you have already started (solar panels + pump) with just "more of the same" or other improvements.

    Going with full solar+battery would only be a solution if none of the other suggestions are practicable for your particular needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Livestock water well

    Thanks for the suggestion of a second pump....I really hadn't thought of just pumping twice as much water during the same time period. Since I have two 24 volt panels, I wouldn't need anymore panels, I could just buy one more pump and hook one panel to each pump.

    If I did want to use a battery system, couldn't I wire the two 24 volt panels to create 48 volts instead of 24 and have enough to run the pump and charge the batteries? I tried a charge controller and it was dead within a week (pretty sure I hooked it all up right...followed the instructions word for word). I got to thinking that I was making the system more complex than it needed to be.

    Thanks again for the suggestion.
  • BB.BB. Super Moderators, Administrators Posts: 28,768 admin
    Re: Livestock water well

    You may need more solar panels for running an additional pump... You need to measure the voltage and current required by your current pump vs what your panels are capable of putting out...

    A simple test, disconnect one of the panels and see what your GPM/GPH flow rate is (and/or run one full day with 1 panel vs 2 panels)... My guess is that you may get only 1/2 (or even less) of your daily water pumping when you disconnect 1/2 of the panels--leading to the assumption that you will need to replicate the whole system (new pump plus new panels).

    Also, really look into the "Linear Current Booster" (if you don't have one, or, if you have a pump controller that does not have LCB). They can really increase useful water flow in the mornings/evenings (basically, they act a bit like a MPPT type solar charge controller--the LCB converts the high voltage/low current of the solar panel into the low"er" voltage/higher current requirement of the typical DC pump motor.


    The problem with your previous try of pumping with a battery system--the usual end result of drawing too much power from too few solar panels/batteries. The standard charge controllers and pump controllers do not do a good job of monitoring the battery's state of charge--and it is easy to kill a battery bank without human monitoring of the system.

    To make a reliable system is not easy or cheap. It can be done--but I would suggest a "battery monitor" with a programmable output (like the Xantrex LinkPro/LinkLite). You can program them to turn off your water pump when the battery is XX% discharged--to prevent over discharging your battery bank. However, in the end, this will be a very expensive system to install and maintain...

    Your current system of solar panel+pump is a much more elegant solution (if you can make it work for you).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Livestock water well

    Thanks for the prompt responses and all the great suggestions. Considering the fact that this system will only be checked about every two weeks, I think I'd better stick to the panel+pump combination. I will check my gph output with one panel versus two panels to determine whether or not to purchase more panels or simply split the two I have.

    Thanks again for all your help.
  • BB.BB. Super Moderators, Administrators Posts: 28,768 admin
    Re: Livestock water well

    And, if you can, do the same GPH test in the morning or evening...

    It is very possible, with fewer panels that the pump will start later and stop earlier--shortening the amount of time, and reducing pumping rates outside of the "noon" peak sun hours.

    Conversely, if you decide you need (one or) two more panels for second pump--you could just try mounting the new panels and see if that gives you enough water without the additional pump. (also, if your pump is the appropriate size; voltage/current; the linear current booster may help a lot too--with just the existing panels).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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