Comparing Soft Pack, Square, and Cylindrical Batteries for Solar Street Lights: Which Packaging Form is Best?

Batteries for Solar Street Lights

Compared with the lead-acid batteries or gel batteries in the past, the lithium batteries commonly used now have better specific energy and specific power, and are easier to achieve fast charging and deep discharge, and have a longer life, so they are also We bring a better lighting experience.

However, there are differences between the quality of lithium batteries. Today we will start with their packaging forms to see what the characteristics of these lithium batteries are and which one is better. The packaging forms are often cylindrical wound type, square stacked type or There are three types of square winding types.

Cylindrical winding type Batteries

That is, a cylindrical battery, which is a classical battery configuration. The cell is mainly composed of positive and negative electrodes, separators, positive and negative electrode collectors, safety valves, overcurrent protection devices, insulators and casings. The casing In the early days, there were many steel shells, but now many use aluminum shells as raw materials.

In terms of size, this kind of battery now mainly has several models such as 18650, 14650, 21700, etc. Among them, 18650 is the most common and the one with the most mature technology.

Advantages

Cylindrical batteries have the best development history and a high degree of standardization. It is easy to achieve unified standards in the industry. The automation level of cylindrical battery cell production is higher than that of other types of batteries, which ensures the high efficiency of cylindrical battery production. , the consistency of the monomer, on the other hand, also reduces production costs.

In addition, the cylindrical battery cell itself has better mechanical properties. Compared with the other two batteries, it can show the highest bending strength under similar dimensions.

Disadvantages

As the batteries for solar street lights, it is not a single battery. It often needs to be formed into a battery pack to work. The cylindrical shape has low space utilization, and the radial heat conduction difference will cause temperature distribution problems. In such an environment , the probability of a large number of cell characteristics being alienated will increase.

In addition, many cylindrical batteries now use steel shells as casings. When forming a battery pack, the weight will be heavier, and there is little room for increase in energy density.

Square winding type Batteries

This kind of battery cell is mainly composed of a top cover, a casing, a stack or winding of positive plates, negative plates, separators, insulators, safety components, etc. It is designed with a needle safety device (NSD) and Overcharge safety protection device (OSD), the shell was generally based on steel shell in the early days, but now aluminum shell has become the mainstream.

Advantages

The square battery package has high reliability and higher space utilization; the system energy efficiency is high, the weight is lighter than the cylindrical battery of similar size, and the energy density is higher; the structure is relatively simple, and the capacity expansion is relatively It is also more convenient. If you want to increase energy density by increasing monomer capacity, this kind of battery is more suitable.

The unit has a large capacity and the system structure is relatively simple, making it possible to monitor the units one by one. Coupled with the design of NSD and OSD, it is safer and more secure to use. In addition, the relatively simple system structure makes it stable. Sexual performance is also better batteries for solar street lights.

Disadvantages

This kind of battery can be customized according to specific needs (mainly in terms of size), so the models of square batteries in the market are not uniform. This non-uniformity also creates a situation where the process is difficult to unify. The quality of the batteries that come out varies.

The level of production automation is not high, and the individual cells are very different. When used in a battery pack, there may be a problem that the life of the battery pack is much lower than the life of the individual cells.

Square stacked type Batteries

It is the soft-pack battery we often talk about. The basic structure of this battery is similar to the above two types of batteries. It consists of positive and negative electrodes, separators, insulating materials, positive and negative electrode tabs and casings. However, unlike the wound type, it is made of The single-piece positive and negative electrode sheets are wound and shaped differently, and the stacked battery is made up of multiple layers of electrode sheets.

Among them, the shell is mainly made of aluminum plastic film. The outermost layer of this material structure is a nylon layer, the middle is aluminum foil, and the inner layer is a heat-sealing layer. Each layer is bonded with an adhesive. This material has good ductility, flexibility and mechanical strength. It also performs very well in terms of durability and heat sealing performance, and is also very resistant to electrolyte and strong acid corrosion.

Advantages

The soft-pack battery adopts a superposition manufacturing method, so it is slimmer in size, has the highest energy density, and is relatively thin, generally no more than 1cm. It is better than the other two models in terms of heat dissipation performance, and with the same capacity, the soft-pack battery Packed batteries are about 40% lighter than steel-cased lithium batteries and 20% lighter than aluminum-cased batteries.

There are also many pole pieces. Each pole piece has a flange and a tab welded together. The current density on the pole plate is well distributed. During the charging and discharging process, the heat is evenly distributed. Moreover, it is a thin sheet design, which is easy to The modules and battery packs make up a very high space utilization rate and are very flexible in terms of size changes. The shape is not limited to square and can be well adapted to different spaces.

Disadvantages

The shell strength of soft-pack batteries is not as good as that of the other two batteries that use aluminum shells or steel shells. They are highly dependent on grouping technology, and after long-term use, the reliability of aluminum-plastic film packaging is relatively low. It is difficult to ensure that the battery body is relatively soft and the contact resistance between the pole pieces may be large, which needs to be solved at the module level or battery pack level, which adds to the technical difficulty.

Like prismatic batteries, although they are flexible in size and can adapt to different spaces, it is difficult to standardize the process, so the quality of the products is also uneven.

The consistency of the battery is also poor. If the battery is operated in an internal environment with insufficient heat transfer such as insulation or high temperature, the battery temperature will rise significantly, resulting in the formation of “hot spots” inside the battery pack, posing safety risks.

Briefly Describe Batteries For Solar Street Lights

Cylindrical batteries (cylindrical wound type) generally use steel shells, but also have aluminum shells. The process is relatively mature, small in size, flexible in grouping, low in cost, mature in process, and good in consistency; it is difficult to design for heat dissipation after grouping, heavy in weight, and low in specific energy.

Square batteries (square winding type), mostly steel casings in the early days, now mostly aluminum casings. Good heat dissipation, easy to design in groups, good reliability, high safety, including explosion-proof valve, high hardness; high cost, many models, difficult to unify the process level, it is one of the mainstream technical routes.

Soft-packed batteries (square stacked type), aluminum-plastic film is used as the outer packaging, the size is flexible, the specific energy is high, the weight is light, the internal resistance is relatively small; the mechanical strength is relatively poor, the sealing process is difficult, the group structure is complex, and the heat dissipation Poor design, no explosion-proof device, easy to leak, poor consistency, and high cost.