Design guide for 600W off-grid solar power system (12V battery system)

A. 2*200W Mono/ Polycrystalline solar panel.

B. 1*40A Mppt solar charge controller.

C. 4*100AH 12V Gel or 1*100AH LiFePO4 battery.

D. 1*600W pure sine wave inverter.

How many batteries do I need for a 600 watt solar system?

In a 12V system, if the solar panel is 400W, the maximum current is 40A when charging the battery, so we choose 40A Mppt solar charger controller in this configuration. If you use GEL or AGM battery with 0.1C charge and discharge current, to make the battery have a better service life, that means you need to use the battery larger than 12V 400AH. And the maximum continuous output current of 12V 600W pure sine wave inverter is 60A, it needs 12V 600AH battery based on the 0.1C calculation. Under normal circumstances, it is impossible to use a 600W inverter to run at full load for a long time. The occasional high current output has little effect on the battery, so the service life of the lead-acid battery used in the system can reach 5 years. But if you use battery with 100AH or 200AH, it will shorten the service life of the battery, wihich is normally less than 2 years. 

For lithium battery, the charge and discharge current is normally 0.5C-1C, which can match the system with 12V 40AH-100AH lithium battery.  Although the price of lithium battery is more expensive than lead-acid battery, the cost of lithium battery is even lower for long term use, because lithium battery usually has a build-in protection board or BMS, LiFePO4 battery can be cycled more than 2000 times, even if it is cycled once a day, it can reach more than 80% of the power after 6 years of use.

What is an off-grid solar power system?


Last modified: December 22, 2021



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