Hi just wanted to get some feedback on my latest project.
A small farm with a well for irrigation currently has a 240v pump installed. They want to try and run offgrid using a 3kw 12v inverter and 6 x 2v 720Ah lead acid batteries (already purchased).
I had a look at the data sheet for the smart solar mppt 150/100 controller which i think could be suitable to charge the batteries. The controller will also be connected to 3 x 450W pv panels.
Can anyone confirm if this will work?
Hi @sunblocks,
You didn’t specified nominal power for the pump and how often does your pump run.
Anyway, it will work in summer, but in winter it really depends on your location, power drawn…
Usually, you have to respect a balance between produced energy, battery capacity and inverter nominal power, they should have close values. Charging power would be a little bit weak in winter I think, but it could work better than I think.
It’s really about how much time do you want your batteries to last in the end.
Try and see, but just so you know, in winter you’ll get about 5 to 15% of nominal solar power, depending on the location (i’m in northern France, with horizontal solar pannels). You can do more of course.
Put your solar system into the Victron MPPT calculator with your location, it will estimate yield throughout the year.
https://www.victronenergy.com/mppt-calculator
Remember lead acid batteries do not like being held at partial state of charge for long periods, they need regular recharges to full. Deep discharge 2V cells will be more tolerant, but still need charging to full from time to time.
Depending on what kind of a pump it is, lead acid batteries are a terrible choice. Pumps usually have large initial start-up currents and can easily damage your batteries in months. I used to run a 600W pump on a 24V/250Ah battery bank with a 3000W inverter. The expensive gel batteries lasted 2 months.
The start-up current of a pump can be 3 to 5 times the power rated of the pump.
What you’re aiming to achieve is definitely possible, but it’s crucial to consider the points that have already been discussed. It is highly likely that you will require additional solar panels. If your pump operates solely during the day with a sufficient amount of solar power, the majority, if not all, of the current will be supplied via the MPPT to the inverter, meaning minimal current will be drawn from the batteries. However, in situations with limited or no solar power, the batteries might experience heavy usage, so it’s essential to factor this into your system design. I personally operate a pump without issues using lead acid batteries, emphasizing the significance of a well-thought-out system design and understanding your requirements and utilization effectively.
Thanks for all your comments. To explain in more detail:
The farm is located in Sardinia, Italy.
The pump is 240v 1.4kw - this matches the maximum output from the solar panels.
I have calcuated that i can run the pump for 3 hours continuously from the battery pack.
To reduce the load on the batteries i will set the pump on a timer so the most it will operate from 11:00 to 14:00 each day during the summer months. For the rest of the year the pump will be set to operate for one hour only.
Hopefully this will mean that on most days the pump will run using pv power.