Hi, I'm currently in the process of building a 3kwp pv system. Im not sure how many batteries I will need. The batteries need to be either 12v or 24v if possible. Thankyou.
Off grid? Grid tied? Inside the artic circle? On the equator? Sounds like you're pretty new so that was a joke. 1x your daily energy usage is about all that typically makes sense for both space requirements and budget restrictions. So if your daily energy usage is 10kWh then you need 10kWH of storage. That's ~420AH at 24v. If it's cloudier for longer than that you adjust your usage, start the generator or go back on the grid.
It depend on your continuous load and how long you want to run on battery for.
3K 24V system
AGM V x Ah x 0.5
Lithium V x Ah x 0.8
2 x 24v 150Ah batteries in parallel will give you 300Ah - example load 500Wh
AGM 24 x 300 x 0.5 = 3600Wh 3.6Kwh
3600 / 500 = 7.2 so approx 7.2 hours run time.
LifoP4 24 x 300 x 0.8 = 5760 5.76Kwh
5760 / 500 = 11.52 so approx 11.52 hours run time.
So you have to have sufficient Solar to run your load and charge batteries - the more batteries you have the longer will take to charge or current to charge them. Also have to account for the poor sunlight and the efficiency of solar panels.
The figures are only estimates
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