Will a 12v DC water pump work if directly connected to solar panels without a battery?

noradawn456noradawn456 Posts: 5Registered Users ✭✭
Most of common DC water pumps can work directly connected to the solar panel, but their biggest problem is stuck. At dawn, the sunlight begins to change from weak to strong, when the output voltage of solar panel achieves the starting voltage, the pump will start to work. But at this time the solar panel can’t provide its full performance, the voltage will decrease significantly because of the load. If it drops to a voltage which can’t maintain the pump running, the pump will get stuck.

Comments

  • mike95490mike95490 Posts: 7,654Solar Expert ✭✭✭✭
    The function of a Linear Current Booster (LCB) is to work around panels not well matched to the motor.   It will cause the motor to run in short useful bursts, instead of slowly turning and not doing any work.   Our host sells them
    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 ,

  • littleharbor2littleharbor2 Posts: 915Solar Expert ✭✭✭✭
    I cant find any LCB on the host site. Lots of pumps and shunts. Do you have a link?

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • PhotowhitPhotowhit Posts: 4,544Solar Expert ✭✭✭✭
    There might be a difference between brushed and brushless motors. I've had no problems running, or I should say a friend hasn't... I bought a cheap brushless water pump with a 12-24 volt range and it ran off a single 55 watt solar panel, in a hydroponics system. I think it was on a timer, so might not have had the situation you are inquiring about, but circulated nutrient rich water in her system.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • mike95490mike95490 Posts: 7,654Solar Expert ✭✭✭✭
    Darn them. Who want's used LCB's ?  now you have to go off-site.  

    NAWS !  why does your store search engine return 20+ hits for Linear Current Booster and shows Shunts and current sensors ?

    Google is your friend

    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. Posts: 27,444Super Moderators admin
    I have sent an email to NAWS about the wrong search results... I think the following is probably what NAWS stocks/sells at this time:

    https://www.solar-electric.com/residential/solar-water-pumping.html?cat=772

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • littleharbor2littleharbor2 Posts: 915Solar Expert ✭✭✭✭
    Trying to figure out what makes an LCB so expensive.  Amazon has a 48 volt, 10 amp version for $435.00  plus $69.99 shipping for a two pound item.  

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • BB.BB. Posts: 27,444Super Moderators admin
    They are, more or less, very similar to MPPT charge controllers (switching power supply).

    Probably not as much volume/quantities as solar charge controllers.

    I agree, they seem to be very expensive.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EquinoxEquinox Posts: 6Registered Users ✭✭
    Most DC pumps will have problems to start as there operation point does not match the operation point of a pv panel.
    If the pump does not rotate it will basically actas a resitor and almost have the panel operating in short circuit.

    A very reliable DC-DC controllers for mid size systems (150 Watt) which is especially developed for deep well pumps is the Shurflo LCB-G75

    sold e.g. by Phaesun:
    http://order.phaesun.com/index.php/accessories-40894/pumpaccessories-40922/shurflo902200pumpcontrollerslcbg-41039/pump-controller-shurflo-lcb-g75.html?___store=default&___from_store=german

    A very reliable pump for small system is the ecocirc D5 vario. This is a pump that can directly be connected to solar panel as it includes a built it MPP controller. Its operating voltage is from 8 to 24V DC..



  • jonrjonr Posts: 951Solar Expert ✭✭✭✭
    I've used a simple brushed DC pump directly connected to panels.  Worked fine without a LCB.
  • BB.BB. Posts: 27,444Super Moderators admin
    Rick are NAWS has fixed the lcb search results.

    More or less, pump torque is proportional to motor current. Solar panels are more or less current sources (50% sun=50% torque).

    The LCB takes solar panel power at low current and fixed Vmp (=Vmp*I sun) and converts to high current & low voltage used to start the pump motor). Solar panels, when there is, at least, weak direct sun, run a constant Vmp and low Isun current.

    If the pump does not start against high pressure, then it does not take much starting torque to get running).

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