How About the Parameter Matching of Solar Panels, Batteries and Loads?

1. Solar Panels
Solar panel parameters are:
No-load voltage and short-circuit current, the product of the two is the power of the solar panel, ie P=UI,
P is the electrical power, unit is watt (W), U is the voltage, unit is volt (V), and I is the current, unit is ampere (A).
There are also working voltage and working current, the working voltage is generally 80%-90% of the no-load voltage, and the working current is generally 80%-90% of the short-circuit current.
2. Battery
The optimal charging current and discharge current of the battery are generally calculated based on the charge and discharge rates of 10 hours. E.g:
The 10AH battery has a charging current of 1A and an optimum discharge current of 1A. The 7AH battery is 700mA. The 40AH battery is 4A. Excessive charging and discharging current will have a certain impact on the life of the battery.
3. How does the solar panel match the battery?
For example, if you want to fill the 12V 10AH battery in one day, you can use a solar panel with a voltage of 15V-18V and a current of 1A. If you need to fill the battery for two days, then you can use a 15V 500mA solar panel. One day is calculated by the sun for 10 hours.
For example, to fill the 12V 40AH battery in one day, you can use a solar panel with a voltage of 15V-18V and a current of 4A, or use four solar panels with a current of 1A in parallel. If it is required to fill the battery for two days, then the solar panel can select 2A of current. When charging, the voltage of the solar panel is 20%-30% higher than the battery voltage.
4. How solar panels and batteries match the load
For example, after the 12V10AH battery is fully charged, it can work for 12 hours with 12V10W energy-saving lamps.
The working current of the 10W energy-saving lamp is I=P/U, 10/12=0.8A.
The battery is calculated according to the 10-hour discharge rate, and the normal discharge current is 1A. Considering the efficiency problem, the lamp can work normally for 8-10 hours. If you use a 40W bulb and the current is 40/12=3.3A, you can only work for 2-3 hours.
Or calculate this, 10W solar panels charge the battery, for 10W lamps to use electricity, according to the ideal state, charging 10 hours can use electricity for 10 hours, but in fact can not reach, can only use 7- 8 hours. If you use a 40W lamp, it can only be used for 2 hours.
Author: Carrie Wong
From WSL Solar Co., Ltd.
WSL Solar has been a quality and professional manufacturer of custom solar panels (or PV modules) and solar solution provider in China since 2006. With our in-house R&D team and management team for over 10 years' experience in solar industry, we are able to design and develop a customized solar module in a variety of sizes, shapes and outputs to meet
our client's specific requirement, and provide solution support start from initial product development stage. For more detail, please visit


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