Running a 12V 4.5A transfer pump of 70W 4A solar panel?

Hi there, I would like to run a 12V@4.5 Amp inline/submersible transfer pump of a solar panel with the following specs:

Max power 70Wp

Open circuit voltage Voc 21.2v

Short circuit current Inc 4.34 A

Max power voltage Vmp 17.8V

Max power current 3.93A

Max system voltage Vmax 1000V Dc

Is the 70Wp sufficient to run the 60W pump and if so is there a converter I need to add to make the system work?

This is a video I got the idea from Running 12V Dc Load Directly From Solar Panel Without Battery - YouTube

Pump specs:

Rule iL280p 12V pump

• Submersible or inline operation

• 1080 litres/hour (18 litres/minute)

• Rated for continuous operation

• Suitable for fresh/sea water or diesel (not suited for petrol)

similar to TCE125 (iL200) except 280 gallons/hour (1080 litres/hour) 1/2" barb type inlet and outlet hose fittings.

• Model iL280P (Red Housing)

• Ok to pump diesel fuel

• 12V@4.5 Amp

• Pump body 102(L) x 40(Dia)mm

Hi Sandra,

It’s hard to know exactly how much power you will be able to draw out of the solar panel throughout the day as solar panels are usually a bit overconfident with their ratings. This is in part due to the way they are rated, typically they are tested in a lab against a 1000 Watts per square meter solar test source, then they measure the power out of the panel.
That kind of illumination level only really happens for a very brief window at midday on a sunny day, if at all. So assume your 70W panel will be capable of less than 70W most of the time.

Your pump motor will also not necessarily draw 100% of its power rating all the time. It will depend on the kind of motor, but most will draw anything from 2 to 8 times their rated current for a second or two as they startup, then settle to the rated values once the motor is up to speed.

We sell buck and boost converters that can regulate the voltage that comes out of the panel, with some efficiency losses, but your pump motor might be drawing what’s close to the maximum output from the panel before many losses are considered.

To determine if the 70Wp solar panel is sufficient to run the 60W pump, we need to consider a few factors.

The 70Wp solar panel has a maximum power output of 70 watts. This value represents the maximum power the panel can generate under ideal conditions. However, the actual power output may vary depending on factors such as sunlight intensity, panel orientation, shading, and efficiency losses.

The pump’s power requirement is 60 watts. If the solar panel can consistently provide 60 watts or more, it should be sufficient to run the pump. However, keep in mind that you might experience some power fluctuations due to varying sunlight conditions, which could impact the pump’s performance.

Now, let’s look at the electrical specifications of the solar panel:

  • Open circuit voltage (Voc): 21.2V
  • Short circuit current (Isc): 4.34A
  • Maximum power voltage (Vmp): 17.8V
  • Maximum power current (Imp): 3.93A

The voltage and current values provided indicate the operating range of the solar panel under different conditions. The maximum power point (MPP) occurs at the Vmp and Imp values. In this case, the maximum power point is approximately 70W (Vmp * Imp = 17.8V * 3.93A = 70.154W).

Based on the specifications you provided, the 70Wp solar panel should be sufficient to run the 60W pump. However, it’s worth noting that the pump’s power requirement is close to the maximum power output of the panel, which means it might not operate at full power continuously, especially if there are efficiency losses or lower sunlight intensity.

Regarding the converter, you mentioned that you want to run the pump directly from the solar panel without using a battery. In that case, you won’t need a converter, as long as the pump can operate at the 12V output provided by the solar panel. The voltage output of the solar panel should be compatible with the pump’s voltage requirement.

It’s important to ensure proper wiring and connections between the solar panel and the pump, following the manufacturer’s instructions for the pump’s electrical connections.

Don’t forget you will only get a “reasonable” solar output for about 4hrs per day, if that.
Cheers Bob

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Thank you so much for your replies guys, very much appreciate your answers.


An interesting idea. The short answer is it might work.

The first question is: what is it used for? most pump applications are intermittent. They run until the fluid is transferred and then they stop. Many pumps don’t like running with no flow, they overheat and burn out. So if the applications is intermittent, there has to be a way of stopping the pump when it is not needed. It follows if it is unattended then there needs to be a way of starting the pump when it is needed.

It is desirable to have a DC-DC converter to limit the voltage to 12V - I see Core have a 150W 13.8V model (13.8 being the voltage of a fully charged 12V battery, the pump specs say for marine use so should handle 13.8 OK). The little converter in the video would not handle the current (they are cheap, I just bought 10 for $1.60 each. They will deliver up to 1 Amp but I wouldn’t ask for more despite their specification).

That said, the maximum output of the panel is 4.34A and the pump will handle 4.5A so directly connecting the panel to the pump could work. It can’t deliver too much current. But it is inefficient.

It may be a better solution to get a lower powered pump which is likely to run more hours of the day if needed. Or more panels. As pointed out by others, it is rare to get the full output of a panel. I have a 1kW system that might get to 900W on a good day but most times in the 300-600W region as the sun is only at the right angle for a short time.

Yes: insufficient information for a clear answer.

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Hi Alan

Thank you for your answer.

The pump is going to transfer water from one tank to another, as the overflow tank has been drained and water now needs to be pumped into it form another tank, so it can fill up and overflow to a tank which is being used as a water supply.

I have thought about the nuisance of having to remember to take the pump off power, despite it only being used intermittently or even just once to top up the drained first tank which can now be left full to just provide the overflow to the next tank which is being used.

I have the 70w solar panel so thought to use that with the little pump which someone recommended on water transfer into a caravan video. There is a power supply, battery bank which I can connect the pump to, but I can’t really visualise the set up in terms of where the power supply is vs distance to the tank being pumped from.

The pump does not need to move the water up much only a couple of metres to account for the distance within the tank itself and across to the other tank just a few metres away and maybe 50cm higher.

I did consider a direct connection to the panel after watching another video which explained the things to be aware of when doing that, but now I am thinking that the pump can be connected to the battery bank which runs the dwelling and just be taken off once enough water is transferred. I’d have to check as to the voltage configuration, but I think it is a 24 volt system, so I guess I’d need a 24v pump to connect it straight onto the batteries.

Hope this provides a clearer picture of what I am trying to achieve.


It sounds like you will be watching over this, turning the pump on and off. As a safety you can arrange overflow of the tank being filled to go back to the tank being emptied. That way if you forget it will just run until you remember (or your battery goes flat). A 24V system is preferable to a 12V system, the electrical losses in cables is a quarter. And I suggest you size the pump to be the smallest that does the job. The head is important - the pump must be able to pump from the lowest point in an emptying tank to the highest point in a filling tank. The other reason for smaller pump is losses in the pipes. I’m not sure of the figure there, but I think doubling the flow has four times the losses for a given pipe. I’m guessing you’ll use something like a garden hose. If it’s a fat pipe (50mm) then the losses are negligible.