Repair technology of plastic shell

With the rapid development of the power supply and distribution industry , the communication industry and electric vehicles, the development of the supporting power supply - the battery industry and technological progress and innovation have also been driven. Due to the excellent cost-effectiveness of lead-acid batteries, in addition to the batteries for portable electronic products and the batteries for aerospace and high-end military use, more than 90% of the energy storage power supplies for electric vehicles, UPS systems, telecommunication facilities (telecommunication centers, satellite ground stations), internal combustion locomotives, automobiles, power stations, substations, emergency power supplies, ships and Guangming projects in power-free areas are using lead-acid batteries. In 2005, the total output of lead-acid livestock batteries in China was 66.45 million kilovolt-amperes, with a total output value of 35 billion yuan; in 2006, the total output rose to 84.57 million kilovolt-amperes, with a total output value of 42 billion yuan, accounting for about one-third of the total output value of the national battery industry (data provided by Dai Jingming, consultant of Jiangsu Shuangdeng Power Group). This shows that the use of lead-acid batteries is very extensive. However, during production, transportation, and use, collisions, falls, and falls may occur; this may cause the battery shell to rupture to a certain extent. If the temperature of a certain process is not well controlled during the injection molding process of the battery shell cover or the internal stress of the plastic shell is not completely eliminated, the possibility of slight cracks in the shell will increase. Microcracks often appear after a period of use, causing micro-leakage of electrolyte. If the glue is improperly used when sealing the battery pole, or due to external force or temperature shock, the sealing of the battery will fail. The slight cracks on the battery shell and the seal at the battery pole cause the battery to fail, which can be repaired to restore the battery function. 2. Repair of slightly damaged lead-acid battery shells using bonding technology 2.1 Scope of application of repairing slightly damaged battery shells using bonding technology Bonding technology is mainly used to repair damaged lead-acid battery shells that are soluble in solvents. Although there are many engineering plastics that are soluble in solvents, the engineering plastics currently selected for lead-acid battery shell materials are mainly ABS (acrylonitrile-butadiene-styrene copolymer) engineering plastics and SAN (styrene-acrylonitrile copolymer) engineering plastics from the perspective of comprehensive performance. The following describes the repair of minor damage to the shell of the above materials. 2.2 Mechanism of bonding repair After the solvent contacts the soluble engineering plastic, it quickly penetrates into the inside under the action of affinity, and the surface becomes soft. Under the action of solvent infiltration, the molecules of the engineering plastics of the same material will penetrate and dissolve with each other. After the solvent evaporates, the bonded material becomes a whole. With the action of external force (adding a certain amount of pressure), the bonding strength will be higher. 2.2 Preparation of adhesive solution Prepare the adhesive solution according to the ratio of 100ml of n-butyl ketone + 25g of ABS (or SAN) plastic particles. After weighing, shake the batching container continuously to completely dissolve the solid particles and form a uniform solution for standby use. The adhesive solution can be used for a long time after sealing. 2.3 Preparation of the repaired lead-acid battery shell The damaged part of the lead-acid battery shell should be cleaned, and there should be no dust, powdery particles, oil stains and electrolyte on the bonding surface and it should be flat. 2..4 Take a clean ABS (or SAN) plastic plate of appropriate size (the size of the plate should be larger than the crack by more than 5mm in all directions, and the thickness should be equivalent to the battery shell wall, and set aside. 2.5 Apply an appropriate amount of glue to the damaged part of the lead-acid battery shell and the surrounding area of ​​more than 5mm, then press the cut plastic plate tightly on the damaged part of the battery shell coated with glue and press it flat. After 12 hours, wait for the glue to completely dry and check if there is no leakage. It can be considered that the repair is complete and can be submitted for use. It should be noted that the bonding surface must be flat and the bonding point must be pressed flat. 2.6 If the repaired battery leaks a lot of electrolyte before repair, sulfuric acid electrolyte with a certain concentration should be added, and it can be submitted for use after charging and activation. 3. Repair of lead-acid batteries with slightly damaged shells using hot melt bonding technology 3.1 Hot melt bonding mechanism Because most lead-acid battery shells are formed by injection molding, the raw materials used are thermoplastic engineering plastics. Thermoplastic engineering plastics will melt at a certain temperature and become viscous or molten. The molten adhesive flows to the damaged part of the heated battery shell and penetrates each other. After cooling, it forms a whole to achieve the purpose of bonding and repair. 3.2 Hot melt adhesive repair method 3.2.1 Preparation of the repaired battery Clean the damaged surface of the lead-acid battery. There should be no acid, dust, oil and granular impurities on the bonding surface. 3.2.2 Repair Use a hot melt gun to heat the hot melt glue stick and heat the repaired part appropriately, so that the hot melt glue stick melts and flows to the damaged part of the battery shell. The glue on the hot melt adhesive bonding surface in all directions should be more than 5mm larger than the damaged gap. The thickness of the adhesive surface of the damaged gap should not be less than the wall thickness of the battery shell. The hot melt bonding surface can be appropriately pressurized to facilitate firm bonding. After natural cooling for 12 hours, check that there is no leakage. It can be considered that the repair is complete and can be submitted for use. Hot melt adhesive repair can be repaired with a hot melt glue stick or a rod (plate) made of the same material as the battery shell as a hot melt bonding material. The latter will have a better effect. 3.2.3 For batteries that have lost too much liquid before melt adhesive repair, the electrolyte of the used concentration should be added to the middle part of the liquid level line after repair and charged and activated before submission for use. 3.3 Scope of application of hot melt adhesive technology to repair lead-acid battery shells Hot melt adhesive repair is suitable for repairing battery shells made of all thermoplastic engineering plastics, especially the repair of battery shell cracks made of thermoplastic engineering plastics without solvents, such as PP (polypropylene), modified reinforced PP (polypropylene reinforced with talcum powder), etc. The slight gap on the cover can also be repaired by the above hot melt adhesive 2007-5-7 bonding method. 4. Repair of lead-acid battery pole seal failure using adhesive bonding technology 4.1 Causes of pole seal failure 4.1.1 The connection seal between the pole and the battery cover of the lead-acid battery mainly uses epoxy adhesives that cure at room temperature. The best use period of the prepared epoxy adhesive is within 45 minutes at room temperature. During the use of the epoxy adhesive, due to gradual curing, the adhesive gradually becomes viscous and wire drawing occurs. At this time, the adhesive should be scrapped. Although the adhesive still has fluidity, it loses its wettability on the bonding surface. At this time, the adhesive should be scrapped if it is not used up. If the operator continues to use it, it will inevitably lead to a decrease in the sealing effect. The problem may not be discovered and tested during the factory inspection, but the seal will fail after a period of use. 4.1.2 During the use of the battery, due to the impact, vibration, bumps and other external forces, the epoxy sealant is broken and the seal fails. 4.1.3 During the use of the battery, due to the hot and cold shock of the ambient temperature, tiny gaps are generated on the adhesive surface, causing seal failure. 4.2 Preparation of epoxy sealant for repairing the pole seal














































Here is a low-toxic, tough, impact-resistant, high-strength epoxy sealant formula that cures at room temperature. Some common materials add toluene to some epoxy glue formulas, and use low-molecular amines as curing agents. This kind of epoxy glue formula is highly toxic, pollutes the environment, and has poor strength.

4.2.1 Low-toxicity epoxy glue formula
E-51 epoxy resin + 651 polyamide resin + benzyl diamine (m-phenylenediamine) + red (or blue) pigment == 100 grams + 25 grams + (9~10) grams + appropriate amount of pigment

In winter or at lower ambient temperatures, epoxy glue is relatively viscous. You can add about 10 grams of 501 propylene oxide butyl ether to the formula (an active diluent for epoxy glue, which participates in the curing polymerization reaction and has a higher strength than using an inactive diluent).

Note: Adding a little pigment is to distinguish the glue used for the positive and negative electrodes.
4.2.2 Preparation of epoxy glue
Accurately weigh a certain amount of raw materials according to the formula ratio and stir them thoroughly. Set aside.

4.3 Preparation of the repaired battery
Remove the old epoxy glue at the connection between the failed pole and the cover, clean it to neutral, and make the bonding surface clean and free of oil and dirt.

4.4 Repair
Pour the prepared epoxy to the connection between the cleaned and prepared battery pole and the battery cover to be repaired, and fill it flat. Curing at room temperature for 24 hours, after inspection, it can be submitted for use after charging (if there is a lot of electrolyte loss, add necessary electrolyte).

Note: The epoxy glue has a service life of only (30~45) minutes. If the glue container is a little hot, it means that the glue has been cured in large quantities and should be stopped.
4.5 Scope of application of epoxy glue
This low-toxic room temperature curing epoxy glue is suitable for the repair of various epoxy glue seal failures, and can also be used in production. This can reduce pollution to the environment and enhance environmental awareness.
5. Conclusion
The repair technology of lead-acid batteries is an application technology that has only been developed in recent years. It is a green and environmentally friendly repair technology. Using adhesive bonding or hot melt adhesive bonding technology to repair battery shells that have been mechanically damaged by collision, falling, or hitting is a very effective repair method; using low-toxic room temperature curing epoxy glue to repair the failure of epoxy glue sealing at the battery pole is also a very effective method. The development and application of lead-acid battery repair technology reflects the understanding, implementation, and support for building an environmentally friendly society. Battery repair prolongs the battery's service life and can reduce the user's expenditure on purchasing new batteries; it reduces the pressure on the supply of batteries, thereby reducing the pollution to the environment caused by the production of lead-acid batteries; it is a very valuable new technology that is worth promoting and applying.