Can I skip the battery?

[thinkmps]

My goal is to part-time run a pump in our small duck pond, it's about 400 gallons (20 inches deep), so I want to move water off the bottom to a bog filter and have it pour back in. We also have a bottom drain that directs the water into our garden (yay fertilizer) so this pump project is just to reduce how often we need to do that.

I'm wondering if I can skip the battery. I found a small pump that can handle 1/4" solids, requires 40 watts. I could obtain a couple of 25-watt panels and an inverter. Would that be enough, ie could the pump simply kick on during the daylight when there is power, otherwise sit silent?

 

[sunshine_eggo]

My goal is to part-time run a pump in our small duck pond, it's about 400 gallons (20 inches deep), so I want to move water off the bottom to a bog filter and have it pour back in. We also have a bottom drain that directs the water into our garden (yay fertilizer) so this pump project is just to reduce how often we need to do that.

I'm wondering if I can skip the battery. I found a small pump that can handle 1/4" solids, requires 40 watts. I could obtain a couple of 25-watt panels and an inverter. Would that be enough, ie could the pump simply kick on during the daylight when there is power, otherwise sit silent?

50W worth of panels running a 40W pump and an inverter means you'll rarely run the pump. 50W worth of panels will only put out their 50W at high noon in conditions that almost never exist. You'll be lucky to get 40W+ for an hour or two a day if you're lucky.

A 12V DC pump with a 12V/100W panel and a DC-DC converter would get you where you want to go, e.g.,

Amazon.com

This would convert the panel output to 12V. You could then use that 12V to direct power a pump up to 72W.

 

[thinkmps]

50W worth of panels running a 40W pump and an inverter means you'll rarely run the pump. 50W worth of panels will only put out their 50W at high noon in conditions that almost never exist. You'll be lucky to get 40W+ for an hour or two a day if you're lucky.

A 12V DC pump with a 12V/100W panel and a DC-DC converter would get you where you want to go, e.g.,

Amazon.com

This would convert the panel output to 12V. You could then use that 12V to direct power a pump up to 72W.

Thanks very much for the explanation and clarifying how much wattage to plan for.

Based on your explanation, it sounds like it is ok to skip the battery, and just let it run when it gets power from the converter?

 

[sunshine_eggo]

Thanks very much for the explanation and clarifying how much wattage to plan for.

Based on your explanation, it sounds like it is ok to skip the battery, and just let it run when it gets power from the converter?

Only if you forego the inverter, i.e., three components:

100W 12V Panel
8-40VDC-12VDC converter
12V Pump

(+ fuses, wires, etc.)

 

[Tomthumb62]

Only if you forego the inverter, i.e., three components:

100W 12V Panel
8-40VDC-12VDC converter
12V Pump

(+ fuses, wires, etc.)

So such a converter would be enough to cover startup surge of the pump? If so that would be nifty.

 

[sunshine_eggo]

So such a converter would be enough to cover startup surge of the pump? If so that would be nifty.

Good point! Not sure now! Depends on the pump size...

 

[Partimewages]

I was thinking there's a 12 volt RV pump that "soft started" but I can't find it. Not sure of the GPM.

 

[Tomthumb62]

I was thinking there's a 12 volt RV pump that "soft started" but I can't find it. Not sure of the GPM.

There’s a $169 device that will make your RV 12v pump run quieter and smoother. I assume it’s some kind of soft start device. But it’s $169 for that convenience.

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[thinkmps]

How do you estimate or know the "startup surge"? This is the pump I'm looking at: https://www.thepondguy.com/product/...28Wh-y1yfcrvPn1u8oJWeIYcCG7Up19hoC7foQAvD_BwE