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

[Daniël Bos]

I'd just keep it simple:
12v panel
Pwm charge controller
Battery

The charge controller will have a load out, which will only be powered when there's sufficient voltage, thus preventing battery/pump damage.

[openspaceman]

2 hours ago, difflock said:

 

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

 

Yes but it's worth reading about how a three stage conttroller enables the batterry charge rate to be optimised and as Daniel says this is simple and the battery can be tiny or simply a large capacitor.

 

https://www.powerstream.com/pv-control.htm

 

Same $ price as our £ price

2 hours ago, difflock said:

 

My  understanding of DC motors is limited to "knowing" insufficient voltage will not run them/"stall" them and eventually burn them out?

Yes this is how we did it in the old commutator days, the current increase as the back emf drops as the motor slows down, this is why there is a large inrush current as the motor starts. My guess is the modern brushless stuff has built in under-speed protection. It will be interesting to have an ammeter in circuit to see how the current behaves as the voltage drops.

2 hours ago, difflock said:

 

 

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?

It won't but if you size your panel to produce sufficient Volts when it's cloudy then it may produce too high a voltage when sunny and therefore a higher current.

 

In your case it may well be that if the pump motor is protected and the motor runs for long enough in bright sunshine you need nothing else.

2 hours ago, difflock said:

 

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 ?

 

 

Yes simple is best but the leisure battery can be small, say a 17Ahr golf cart type. As Daniel says  the charge controller  could handle the battery protection too. I'd still consider swapping the battery for a large capacitor.

 

I still tinker, am making a headlight on buzzer when the ignition is off as I keep flattening the battery on an old car, just a buzzer and diode circuit.

 

 

[difflock]

Daniel, and OSM,

I "missed" the fact that the charge controller "doubled up" as a battery guard, or should, if the correct one is sourced.

thanks Daniel.

And yes, I have grasped the battery need only be big enough to "smooth" the voltage/current input/output.

cheers again

mth

[Macpherson]

So whether battery or capacitor would the charge controller supplied with the original solar panel kit not do the job ?  Just presumed that would be it's purpose, cheers.

 

 

 

[difflock]

yes

[Macpherson]

16 minutes ago, difflock said:

yes

So the whole charging system less the battery for £40 ish ....not bad at all

[openspaceman]

1 hour ago, difflock said:

yes

What I didn't mention is that as the solar charger power is smaller than your pump requirement even in full sunshine it means the pump will be switched on and off by the  under voltage feature of the charger. Now this may not matter to you but it will mean the battery is constantly cycled from around the low charge voltage, 11.5V ish and the state of chrge when the solar charger cuts back in, this could mean the battery charge discharge cycles will shorten its life.

[difflock]

Oops,

OSM

I had started looking at 100W solar panel arrays, for this very reason!

To drive my 54W pump

cheers again

mth

[aspenarb]

Everything solar I have seen to date has been very underwhelming , some of the output figures are based on blazing sunshine directly onto the panel and unless the panel tracks the sun you are highly unlikely to get a fraction of the claimed output.

 

If its just water you want to lift  build a small version of windmill pump, beat that with yer urlectrickery

 

Bob