Turn off power to pump when sun goes down

[Stuee123]

Hi, im setting up a small pump to push through solar hot water to my spa.
I have a 190w solar panel >12v regulator. 90ah 12v battery and a small 12v pump. 50Lph/.
I want to have some sort of sensor so when the sun is up and the solar panel is charging the battery then the pump runs, when its dark its off. This way it works for 2 reasons. 1 if no sun then no heat to the water solar heat pipes so no point in pumping the water. 2nd I dont want the pump running if the battery isnt getting its charge back or it will just flatten it.

Any ideas/ schematics?

Cheers

 

[augustinetez]

Well, you already have the 'sun sensor' - the solar panel.

All you need to do is detect when there is voltage from the panel which might be as simple as 1 transistor, a few resistors and a relay with snubber diode.

(The dog has decided to have a nap on my lap so I'm typing this one handed and will draw up my idea when he gets off.)

 

[Ramussons]

Why not run the pump directly off the solar panel? No sun, no pump.

 

[AnalogKid]

What are the peak and steady-state current requirements for the pump? As above, a simple power transistor switch should suffice, although I would add a 2nd, small signal transistor and hysteresis to prevent overheating in the power transistor.

A more simple, but a bit less efficient, solution is one relay with just the right coil voltage to act as a solar panel voltage level detector. Because a relay's pull-in current is higher than its holding current, it has a small amount of hysteresis built-in to prevent contact chatter.

Pump running current?
Peak voltage out of the solar panel?

ak

 

[davidganthony00]

can solar panels charge with hot conditions without necessarily being sunny?

 

[gophert]

can solar panels charge with hot conditions without necessarily being sunny?

No, a solar panel converts light to electricity and is directly proportional to the amount of photons hitting it - regardless of temperature. Overcast days make less power than sunny days but some light makes some power - it doesn't have to be a sunny day.

note, there is some temperature effect when you are outside the design specifications of 60 to 90F. Efficiency drops about 3 to 4% for every 10-degrees F change (above or below the design range.

 

[davidganthony00]

thanks for taking the time to reply and well explained.