How does the cut off and charge work

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Benchallis
Benchallis Registered Users Posts: 1 ✭
in Solar Beginners Corner #1
Hi all i have recently installed a solar water pump running of 3 x 12 volt battery and the pump in on a float switch  

My question is when the battery run low and stop and the float switch is I still on is it possible to charge the battery without the pump wanting to draw the power?

The site does not get a regular visit so ideally I need to be able to charge the battery without the pump kicking in while I am not there 

Any suggestions would be greatly appreciated 
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    As long as float switch says pump, the pump will try to pump, perhaps fatally draining the battery, unless you buy and install a
    Low Battery Cutoff Switch.
    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 ||
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited January 2021 #3
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    Welcome to the forum @Benchallis

    There are charge controllers which can be configured for use as  a load controller or diversion controller, Morningstar TS series is an example. When used as a load controller it is programmable to cut the load when battery voltage drops below a safe threshold, from 75% state of charge down to 8%, low cutoff values are not recommended other than for critical applications such as in telecommunications. These controllers can be programmed for a single application at any time not multiple, if the pump is the only load this may work.

    NOTE ! These controllers can not have an inverter to them as a load, a DC pump would be OK

    There are ways to use an inverter in load control mode, Can you provide details on what equipment you have?  

    There are also  voltage sensing relays available which could be used in a similar way but it is essential that the batteries actually get charged to prevent cronic undercharging, this requires careful setup.


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
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