In recent years, solar energy has developed rapidly and spread to all fields, thanks in large part to the decline in the cost of solar cells and energy storage. As an important part of solar energy products, the cost reduction of solar cells is promoting the rapid development of solar energy industry. In China, from the overall development trend of the solar street lighting industry, some institutions expect industry-wide production by 2020 is expected to be around 20.25 million.By 2020, the solar street lamp market capacity will reach 60 billion yuan.
With the development of new energy vehicles, lithium battery technology becomes more mature, cost decline, so that lithium battery in the use of solar street lamps become possible. Lithium batteries have more advantages over lead-acid or colloidal batteries. Because of the high energy density of lithium batteries, the volume of the same capacity becomes smaller. It makes the integration of batteries and lamps possible, and also providing more imagination space for the design. It makes also solar street lamps more aesthetic, and making transport installation and maintenance easier; The longer cycle life of lithium battery, also makes solar street lights longer lifespan, this is undoubtedly good news for photovoltaic lighting.
With the new energy vehicle battery life problem, there are many batteries were eliminated. In the environment that national policy and regulations are not standardized, and the secondary application technology are immature. Many manufacturers desire to be able to deal with these batteries on low-cost processing, or even sold by tons, that makes the price very low, some costs may be normal batteries 1/5-1/10. How long can these batteries last? The seller’s psychology has no bottom.
So these products themselves are not guaranteed, and because many of them are dealing on case, the transaction is not guaranteed after completion. Where did these eliminated batteries go? What is the use? It is understood that many of the batteries that have been eliminated are flowing into the solar street lighting industry, which has made the solar street lighting market worse, resulting in a more uneven product, the price and quality gap becomes greater. Not only that, some manufacturers even openly claim that the car’s battery life can be eliminated by 15 years, with a warranty of 5 years. I am also wondering: how dare these solar street light seller can promise their light can use more than 15 years?
Because this culture spreads faster in this industry, really beyond imagination. It seems that overnight, will let everyone feel that solar street lights should use such batteries, so in order to find out the normal battery and eliminate the battery in the end what difference, We specially combined with some battery suppliers to do industry survey, finally we get some data, and through data and analysis to let everyone understand the secret in the middle.
1). Analysis from a key technology perspective
What is the ladder utilization? For example, for example, the battery is used in new energy vehicles, the battery is fully charged 100% energy, after a period of time, the battery capacity will decay from the car decay ingress edifying the battery. The battery capacity from 80%-20% of the interval can be used ladder utilization, such as the application in low-speed cars, electric tricycles, Charging station energy storage and so on. In China, the government also promote this, but the use of ladders can not be applied casually, the core of the ladder utilization is the need for a number of complex testing and analysis of native products, scientific judgment of its life cycle value and reusability. So as to design the product in line with the gradient level and application areas. In addition, the use of ladders requires a rigorous inspection process, in the relevant legal provisions, the operating procedures of decommissioned lithium-powered batteries should have a strict inspection process and high safety requirements to carry out. However, the key technology used by the ladder is not mature enough, and some technical difficulties have not been solved.
The key technologies used in the rungs are two: one is discrete integration technology, different battery pack technology, disassembling needs to be integrated according to the performance, life of different unit batteries, and the other is the whole life cycle traceability technology: soC, SOH, SOP technical indicators provided by BMS to estimate.
In order to maximize the value of the use of ladders need to be strictly in accordance with the standard process control, but in practical application, many manufacturers do not master the use of ladder technology, and because of the high cost of testing, many manufacturers have not gone through the process test, directly sell the obsolete batteries, without any quality assurance.
2). Analysis from a chemical point of view
The main chemical of the battery are composed of positive negative diaphragm electrolytes, etc. , and these materials themselves have a life cycle. In the case of lithium phosphate, the cycle life can be up to 2000 times, so as the number of cycles increases, the chemicals in it change, making the entire life cycle may be uncertain. Take Shenzhen’s pure electric taxi as an example, I once talked with the driver, their electric taxi to charge twice a day, and this is a large current charge and discharge, a day by 2 cycles, 3 years of the number of cycles for 2 x 365 x 3 x 2190 times. The lithium phosphate core has 2,000 cycles, while more string-link-ups on electric vehicles do not reach that many cycles. If the electric car after 3 years of operation eliminated the battery, the cycle life has been more than 2000 times, and from its own chemical characteristics, the life can be used can no longer be guaranteed, which is why no battery manufacturer dares to such a battery to warrant the reason.
Ladder battery secret sale scene secretly caught on camera
3). Analysis from the point of view of actual test
In order to let users understand the internal structure of the obsolete battery more intuitively, there are institutions to the elimination of the battery cells sampling test: a total of 250pcs, of which 80pcs due to rust or other reasons, can not measure the voltage.
Comparison of normal batteries (left) and rungs (right)
Through testing, we also found that the core of the internal resistance and voltage are very different, so that the consistency between the batteries will be much worse. Such a product will be strung in parallel after there will be a greater hidden danger.
Therefore, the elimination of the capacity of the core, pressure drop, internal resistance, circulation and other performance in a very low and unstable state, not only can not meet the assembly requirements, and even for single use, its capacity attenuation and power loss rate is also extremely unstable, the user experience must be extremely poor. And lack of liquid, lithium such internal defects, represents an unstable security risk.
4). Analysis from the perspective of the working environment
Many manufacturers will be removed from the car battery on the solar street lamp, is this feasible? Solar street lamp application scenario is actually as complex as the electric car, the working environment is worse, the use of the car is not so continuous, there is rest time, and the car generally parked in the underground parking lot, can avoid the sun, heavy rain and other bad weather. But solar street lights are 24-hour work, every day, no stop, and used outdoors, will encounter storms, snow, sun, wind and sand and other extreme weather. Therefore, it is not appropriate to use the batteries that have been eliminated from the car on solar street lamps with more complex working environments.
5). Analysis from the properties of solar street lamp engineering
Solar street lamps are often as a city infrastructure equipment, service is the citizens, related to the people’s real life, so the reliability of products, safety, stability requirements are higher. If the eliminated battery used in the service of the public on the solar street lamp, there is a great safety risk. The eliminated battery itself has a greater hidden danger, because the eliminated battery itself has been a long time charge and discharge cycle, life and chemical characteristics have not been guaranteed, just like a person who has done heart bypass surgery, but also let him run a long-distance pull pine. He may not have problems, but the risks are extremely high. But solar street lamps as an infrastructure project product, this risk is unacceptable, this is related to the lives and safety of the masses.
But many manufacturers in order to earn quick money, regardless of hidden dangers, will be eliminated batteries on the solar street lights, will not consider the late quality assurance problems, and even some manufacturers will be the warranty time void, but when the real problems to find manufacturers, but no sound.
So, in my opinion: If you have requirements for the life and quality of solar street lights, please do not choose from the car to be eliminated from the battery used on solar street lights. If you don’t ask for the quality, I’m not opinion guide, the specific choice is your own.
But I still suggest that no matter manufacturers, engineers, or even government departments, should choose high-quality products and services to the public, responsible for products, users responsible for social responsibility.