How many batteries do I need for a 3kW off grid solar system?

5. Design guide for 3kw off grid solar system with battery (24V or 48V battery system).

A. 6*300W Mono/ Polycrystalline solar panel.
B. 1*80A @24V battery or 1* 40A @48V battery Mppt solar charge controller.
C. 8*100AH 24V ( 4*100AH 48V) Gel or 1*300AH (3*100AH) LiFePO4 battery.
D. 1*3000W pure sine wave inverter.

How many batteries do I need for a 3kW solar system?

1.Lead-acid battery for 3kW solar system, in the statement of 24V, 3000W/24V=125A, if it needs to stay in the best condition, and run at full load for a long time, we suggest you to use 125A*10H=1250AH, 13 batteries in parallel. If  itis 48V, it needs 14 batteries, 7 in parallel and 2 in series. Such configuration can satisfy the running of this system, and is good for the service life of the battery. If you occasionally use with 3000W load, just 1000W in normal, that will be fine to configure  according to 1000W system. It has little effect on the service live of battery when in a short time use. Why we need such large battery system? If the charge and discharge current of the lead-acid battery is 0.1C, (most charge and discharge current of lead-acid battery is 0.1C on the market), the charge and discharge time is 10 hours, it is its own original design. We have tested, if charge the 100AH battery with 40A Mppt solar charge controller, the battery is exhausted and unusable in less than 45 days.

2.LiFePO4 battery for 3kw solar system, LiFePO4 is different from lead-acid battery, it is designed with charge and discharge current 1C, (also have charge and discharge current 0.2C-0.5C on the market). If you don't need to run at 3KW for a long time, LiFePO4 battery is very suitable for the system. Its weight and volume is much smaller than lead-acid battery. 1C to charge or discharge battery for one hour  will not effect the service life of the battery. LiFePO4 battery can cycle more than 2000 times, even if it is cycled once a day, it can also be used for more than 6 years and keep its attenuation less than 20%. In this system, we just need 150AH 24V (75AH 48V) LiFePO4 battery, which will save space and lower the cost.


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