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12v 24v Solar Battery Caculation

Shenzhen Sinoli Electronic Co.,Ltd | Updated: Jan 13, 2019

【 CASE 】Installation site: Taiyuan Load 2 50W Load Input Voltage 24 V Continuous 3 Rainy Days Work 8 hours a day

1. Solar panel calculation

2*50W*8H/0.6/4H=340W (total power consumption/system utilization coefficient/effective sunshine time)

2. Battery calculation

2*50/24*8* (3+1)/0.7=200AH (total current*self-sustaining time/margin coefficient)

The sunshine coefficient in Taiyuan is 4.83.

50W*2*8/4.83/0.9=184W (solar panel power=load power*working time/loss 0.9/average effective light)

50W*2*8*3/24/0.7=143AH (Battery Capacity=Load Power*Working Time*Continuous Rainy Weather/Battery Voltage/Charge and Discharge Coefficient)

calculate the current:

Such as: 12V battery system; 40W lamp 2, a total of 80 watts.

Current = 80W_12V = 6.7A

Second: Calculate the battery capacity requirements:

For example, the cumulative lighting time of street lamps per night should be 7 hours (h) of full load.

(If it opens at 8:00 p.m., closes Road 1 at 11:30 p.m., opens Road 2 at 4:30 a.m., and closes at 5:30 a.m.)

It is necessary to meet the lighting requirement of 5 consecutive rainy days. (5 days plus overnight lighting on rainy day for 6 days)

Battery=6.7A*7h*5+1 days=6.7A*42h=280AH

In addition, in order to prevent the battery from overcharging and overdischarging, the battery is generally charged to about 90%, and the remaining discharging is about 20%.

So 280AH is only about 70% of the real standard in application.

Calculate the peak demand of battery panel (WP):

The cumulative lighting time of street lamps per night is 7 hours (h).

The average daily effective illumination time of the battery board is 4.5 hours (h);

Leave a minimum of 20% of the reserve for battery board requirements.

WP_17.4V=(6.7A*7h*120%) and_4.5h

WP_17.4V = 12.5

WP = 217 (W)

The daily sunshine time of 4.5 hours is the sunshine coefficient near the middle and lower reaches of the Yangtze River. In addition, in the solar street lamp module, line loss, controller loss, and power consumption of ballast or constant current source are different, which may be about 5% - 25% in practical application. So 162W is only a theoretical value, which needs to be increased according to the actual situation.

Solar Street Lamp Scheme:

Relevant component selection:

24VLVD Poleless Lamp: Select LVD Poleless Lamp Lighting, LVD lamp has long service life, soft lighting, reasonable price, can realize power regulation in the scarce pedestrian period at night, which is conducive to power saving, thereby reducing the configuration of battery panels and cost saving. About 80 LM per watt, the light attenuation is less than or equal to 5% per year.

12V Battery (Series 24V): Choose lead-acid maintenance-free battery with moderate price and stable performance. Solar street lamp is preferred.

12V battery panel (24V series): single crystal positive with conversion rate of more than 15%;

24V controller: MCT charging mode, with power regulation function (additional information);

6M lamp pole (with beautiful appearance, durability and reasonable price)

I. 40 W Option Configuration I (Conventional)

1. LVD lamp, single channel, 40W, 24V system;

Effective illumination in local day is calculated by 4 hours. Discharge time of 10 hours per day (take 7:00 p.m. - 5:00 a.m. as an example). Satisfy 5 consecutive rainy days (plus 6 days of electricity used overnight before rainy days).

Current = 40W_24V = 1.67 A

Calculated accumulator = 1.67A*10h*5+1 day

=1.67A*60h=100 AH

Reserve 20% capacity for battery charging and discharging, and the actual current of street lamp is over 2A (plus 20%).

Losses, including constant current sources, line losses, etc.

Actual battery demand = 100AH plus 20% reserved capacity plus 20% loss


Actual batteries are 24V/150AH, requiring two groups of 12V batteries totaling 300AH.