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ggi2020 avatar image
ggi2020 asked

What size battery storage is recommended for a 3kwp pv system?

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.

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seb71 avatar image seb71 commented ·

Off grid or you have grid available?

Will you use an inverter or it will be a DC only system?

If you will have an inverter, how big it will be? If 3000VA or larger, go for a 48V system (48V battery).

What type of battery (lead-acid, LiFePO4, etc.)?

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nobodyspecial avatar image
nobodyspecial answered ·

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.

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southsideph avatar image
southsideph answered ·

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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