With the increasing scarcity of non-renewable energy resources on earth, the development and utilization of renewable energy has attracted more and more attention. For example, solar energy resources are inexhaustible green and environmental protection new energy products. The state has also issued relevant policies to encourage and support the development and utilization of solar energy.

In the lighting industry, solar street lamps are one of the hottest products at present. They are indeed much more expensive than ordinary circuit lamps in terms of price. However, considering long-term energy conservation, environmental protection, and later maintenance, the comprehensive price of solar street lamps is much cheaper than traditional street lamps.

Today we want to explain to you how to calculate the configuration of lithium battery solar street lamps?

We take a 40w led light source as an example: the customer requires 8 hours of lighting every day, taking the sunshine peak value of 3.9 as the reference, and the cloudy and rainy days are calculated as 3 days.

How to calculate the capacity of lithium battery?

Let’s take 18650 ternary lithium battery as an example:

Known conditions: the nominal voltage of a lithium-ion secondary battery is 3.7V; The system voltage of a 40 wled lamp light source is 12V; The platform voltage composed of three lithium batteries in series is 11.1v, and the standard charging voltage of the battery board is 17.5V.

First, let’s popularize the conversion of ah (ampere-hour) and wh (watt-hour) units
Wh (watt-hour) and ah (ampere-hour) are both ways to measure battery capacity

Ah is a unit to measure the capacity of power storage equipment. It means that it conforms to the discharge curve (a curve similar to inverse proportion). At this time, it can meet the result that the product between current (ampere) and discharge time (hour) is the capacity unit [ah].

We often see a number in wh next to MAH.

Work done by the battery W = UIT = voltage (V) * current (a) * time (H),

The voltage U * current I = power P (watts, English letter “W”)

Therefore, the work done by the battery W = P * t, the unit is wh

Ah = work (W) / voltage (U)

Back to the point,

Daily power consumption of 40 wled light source = 40W * 8h = 320wh

The design of solar street lamp shall consider the cloudy and rainy days of the day, taking 3 days as an example,

Then the total power required by 40wled light source in 3 days = 320wh * (3 + 1) days = 1280wh

Then the capacity of lithium battery = work (W) / voltage (U) = 1280wh / 11.1v = 115ah

How to calculate the power of solar panels?

Daily capacity of lithium battery = 115ah / (3 + 1) days = 28.75ah

Solar panels receive sunlight during the day, and the power used to charge lithium batteries is 20-30% higher than that used by light sources every night

Then the daily charging capacity is 28.75ah * 1.3 = 37.375ah

According to the effective sunshine duration per day, it is calculated as 3.9 hours

Then the daytime charging current = 37.375ah / 3.9 = 9.58a

Then the power of solar panel P = u * I = 17.5V * 9.58a = 167.65w

Based on the charging efficiency of the mono solar panel is 80%,

Then the actual required solar panel power = 167.65w / 0.8 = 209.5625w

If it is an 18650 lithium iron phosphate battery, the nominal voltage of a lithium-ion secondary battery is 3.2V; The platform voltage composed of four lithium batteries in series is 12.8v.

If the system voltage is 24V, the standard charging voltage of the solar panel is 35V, the platform voltage of the ternary lithium battery is 22.2v, and the platform voltage of the lithium iron phosphate battery is 25.6v.

The charging efficiency of poly solar panels is 75%.

When calculating the configuration of lithium battery solar street lamps, we must comprehensively consider the power demand of customers, such as daily lighting time, sunshine peak value, and rainy days in each city.

Otherwise, the unreasonable configuration of solar panels and lithium batteries will have a great impact on the normal operation of the system, which will not only affect the service life but also increase the after-sales maintenance cost. If the configuration is small, Insufficient power generation will cause irreversible use consequences.