Solar powered water pump (kit?), for the veg garden

[eggsarascal]

10 minutes ago, Macpherson said:

Hi, interesting thread,..... I'm putting together a similar system to you to keep batteries charged for off grid power, I rarely find anything on Amazon to be cheaper than ebay, cheers. 

 

http://www.ebay.co.uk/itm/20W-solar-panel-kit-with-controller-for-camper-caravan-boat-20-watt-charger/122630270712?epid=16015680039&hash=item1c8d556ef8:g:EJgAAMXQwwlSABHG

What batteries are you wanting to keep charged?

[Macpherson]

49 minutes ago, eggsarascal said:

What batteries are you wanting to keep charged?

Hi, nothing very Tesla I'm afraid for the time being... I've got access to a ready supply of s/h car batteries  many of which may have been replaced unnecessarily and can last years just running lighting / fans, etc in a 12 v system.

My old workshop ran this way for years and although I'm not off grid, I plan the same again in my new place especially outside lighting, my electricity use is small and I don't want to add to my bills, so this would seem the easy way to go, cheers.

[difflock]

Thanks McPherson,

I got an old 12V tractor battery that should do, to be charged from a panel kit like you linked to.

And

Then use the car type undervoltage protection kit to safeguard the motor,

I can let the pump motor run ad-infinitum, while the sun is shining and the battery is charged,

and let the water overflow back down into the "well",

perhaps past a waterwheel for aesthetic effect!

cheers

marcus

 

P.S.

How does the solar controller "dump" the excess voltage/current from the panel, after the battery refuses to accept any more charge,

simply put it through a resistor and dump as heat?

 

Anyway the 20W Solar panel per McPherson

A 12 V battery

a "battery Guard" at £18.00

Plus, this pump & see link,

https://www.ebay.co.uk/itm/DC12V-Speed-Adjustable-Brushless-Water-Pump-Solar-Pump-DC50K-12120A-1260L-H/282909534103?epid=1985627580&hash=item41deb8e797:g:yQcAAOSwTmtawoJn

 

Should work

To pump say, at worst 1000l per day = enough

 

Edited May 6, 2018 by difflock

[openspaceman]

8 hours ago, difflock said:

Then use the car type undervoltage protection kit to safeguard the motor,

 

It's the battery that it safeguards

Quote

I can let the pump motor run ad-infinitum, while the sun is shining and the battery is charged,

Remember the battery charging takes some of the power, which in marginal sunshine is why a capacitor may be better.

Quote

How does the solar controller "dump" the excess voltage/current from the panel, after the battery refuses to accept any more charge,

simply put it through a resistor and dump as heat?

I imagine it just uses a MOSFET to cut the current, the panel then is simply open circuit and the heat is dissapated in the panel instead of the current taking energy out.

Quote

 

Anyway the 20W Solar panel per McPherson

A 12 V battery

a "battery Guard" at £18.00

Plus, this pump & see link,

https://www.ebay.co.uk/itm/DC12V-Speed-Adjustable-Brushless-Water-Pump-Solar-Pump-DC50K-12120A-1260L-H/282909534103?epid=1985627580&hash=item41deb8e797:g:yQcAAOSwTmtawoJn

 

Should work

To pump say, at worst 1000l per day = enough

 

That pump has 8l/min output at 7 metre head. At full flow it requires 54W=4.5A and 12V.

 

I wonder if it would be cheaper to find the 12V pump out of a Toyota prius, as the impeller has permanent magnets and the coils that give a brushless rotating field are sealed, I've no idea what head it will pump.

Edited May 6, 2018 by openspaceman
misread output chart from ebay listing

[difflock]

OSM

 

Thank you, your advice is genuinely apreciated.

 

I understood the "battery guard" protects the battery from over-discharging, or perhaps more correctly ensures sufficient charge remains in the battery to start the vehicle the battery is mounted in,

based on the dropping voltage from supplying ancillary devices,

but in so doing it will thereby protect the pump from damagingly low voltage, or so I figger?

I understand 12V Lead Acid batteries, but not capacitors, and I got a battery already.

 

I am not concerned about marginal sunlight conditions, since I only need to irrigate during, for us, exceptionally hot/sunny weather, when the panel should be working optimally.

btw

the pump I linked will pump to a max of 12m head(at zero flow) and  7l/min my needed 7m of head, per the attatched graph(s) ,the one labelled in red ink.

Or the pump I order certainly will as per the specification table presented.

That site impressed me with the data/facts so clearly laid out.

cheers

marcus

Edited May 6, 2018 by difflock

[openspaceman]

1 hour ago, difflock said:

understood the "battery guard" protects the battery from over-discharging, or perhaps more correctly ensures sufficient charge remains in the battery to start the vehicle the battery is mounted in,

based on the dropping voltage from supplying ancillary devices,

but in so doing it will thereby protect the pump from damagingly low voltage, or so I figger?

Yes I see what you mean now, the battery guard protects the battery from being too deeply discharged, in doing so it means that the pump will always get enough voltage to run rather than just sitting there humming.

 

It will be interesting to see how it manages.

[eggsarascal]

7 minutes ago, openspaceman said:

 

 

It will be interesting to see how it manages.

Do you think it will manage OSM?. 

[difflock]

OSM,

You said;

"How about nicking a super capacitor from a pimped up Corsa and having a relay running the pump only when the capacitor is at 12V. This way the motor isn't draining current below its stall speed."

 

Since the battery I intended to use is apparently "goosed", having failed to trickle charge overnight,

 

could you better explain/describe the circuit/components needed for to get the above set-up to work?

 

cheers

marcus

[openspaceman]

8 hours ago, eggsarascal said:

Do you think it will manage OSM?. 

It's difficult to decide, for a start we don't know how much bright sunshine Marcus has. I do know in my latitude that over a year each Watt of installed PV capacity will generate 0.75kWh over a year and 80% of that will be from May to September. This is no problem as he only wants top irrigate in summer.

 

Marcus's tank is about 3000litres and at 6metre head his pump will deliver 8 litres/min. So IF he supplies 12V to the pump it can empty the tank in about 6 hours. The average solar energy received is about 4kWh/day per square metre in summer so it's only about sizing.

1 hour ago, difflock said:

 

could you better explain/describe the circuit/components needed for to get the above set-up to work?

 

cheers

marcus

First the thing about super capacitors is that they mustn’t be overcharged. Given that a solar panel only delivers a fraction of the voltage when shaded  by cloud compared with in full sunlight this means the charge voltage from it will vary greatly. Also as super capacitors are rated at about 2.6V you need 6 of them in series and a means of making sure each one only receives <2.6V. This normally means having an equalising circuit around each capacitor. Ones sold in packs for boost starting a car will have this built in.

 

The quandary is should you have a 12V 54W panel that only works in full sunshine, in which case you can connect the pump directly to the panel and have the pump stalled when the voltage is too low to run it or should you have a 20 or 30V panel and higher power and then control the output. If you already have the panel I would just try this first. I have been given one of those panels that you stick inside a car windscreen when parked up, charging via an always live cigar lighter socket, it seems to use most of its power flashing a built in diode

 

I think I would opt for the 12V panel a germanium diode then the super capacitor pack and a simple circuit using a Zener diode  to trigger a transistor and switch the pump via a latching relay. Then when the pack is above 12V in bright sunshine the pump runs constantly. If the panel is shaded then it still trickle charges the super capacitor until it reaches 12V, then the zener triggers the relay and the pump runs on the energy stored in the super capacitor until the voltage drops.

 

These super capacitors are hundreds of Farads and will run the pump for minutes whereas the bass booster capacitors in car audio systems are 1 or 2 Farad and will only run the pump in 1 or 2 second bursts.

 

You could just use the type of controller

 

https://www.water-garden.co.uk/prod/solar-charge-controller-10-amp

 

and simply have the capacitor where the battery should be

[difflock]

OSM

thanks for the above, 

 

I do not possess any of the needed components at present.

(i) I think I looked at a very similar/looked identical visually solar charge controller from "Photonics" on Ebay

 

My  understanding of DC motors is limited to "knowing" insufficient voltage will not run them/"stall" them and eventually burn them out? and excess voltage will overspeed them/kill them quicker, but that they cannot "draw" excess Amps, (i.e. can connect direct to a 12V automotive battery that can supply hundreds of Amps to a starter motor, without harm),

but quite how lower than max Amps affects them I am not sure?

 

I prefer to source "off-the-shelf" stuff rather than faff about soldering and wiring individual electronic components.

 

And I am minded to simply purchase a new 12V liesure battery, and stick to simple 12V DC circuits which (I imagine) I understand.

So,

(i)Solar panel(s) bought complete with solar battery charging unit.

(ii)12V battery

(iii) battery guard

(iv) 12V pump

 

simples ?

 

 

 

marcus

 

 

Edited May 7, 2018 by difflock