Principle and design analysis of waterproof battery

The ambient humidity and temperature difference of water, gas and heat energy meters are large, and it is difficult for ordinary primary lithium batteries to meet the requirements of use.

Often the battery in normal use is additionally discharged due to moisture, increasing capacity loss and premature failure. It cannot meet the service life requirements of the instrument. According to the actual needs of battery use, combined with the experience of batteries, waterproof battery appeared.

1. Waterproof battery principle analysis

The open circuit voltage of lithium battery is about 3.65V, which requires moisture-proof and high temperature during storage and use. The reason is that if the battery is placed in humid air or suddenly switched from a low temperature environment to a high temperature environment, the surface will absorb moisture and condense to form a water film.

The cathode and anode of the waterproof battery will be discharged through the water film and the water will be electrolyzed. At the same time that the above electrolyzed water reaction occurs, the waterproof battery is also corroded by oxidation at the cathode extremity and increases the conductive resistance.

The result is not only to consume the capacity of the battery (commonly known as "leakage" or "short circuit"), but also to corrode the cathode terminal of the battery, or cause the connecting wire of the cathode to be broken, so that the battery fails abnormally.

If the batteries are used in a special environment, the air is humid or contact with water is unavoidable. In this case, the battery is required to be waterproof. According to the electrolysis reaction mechanism of water, as long as one of the electrodes in the cathode and anode is insulated, the electrolysis reaction will not occur.

2. Measures taken by waterproof battery

The waterproof battery can be used in a humid environment for a long time, or even immersed in water. The batteries with this waterproof structure is immersed in salt water, and the performance of the waterproof battery is stable. The open circuit voltage is stable and unchanged, which completely solves the problem of moisture failure of primary lithium batteries in water, gas and heat meters.

This ensures the service life and improves the reliability of the instrument. After years of use, waterproof battery has been widely recognized and have now been promoted and used in large quantities. Waterproofing measures can be taken in one of the following scenarios:

• The waterproof battery is potted as a whole.
• Anode insulation.
• Cathode insulation.

A certain amount of heat is generated during the discharge of the waterproof battery.  The first two schemes are not conducive to battery heat dissipation, especially for power batteries, in the case of abnormal battery (such as short circuit, etc.) after the explosion-proof groove at the bottom of the anode is sealed, it will greatly increase the danger of the battery.

The last scheme is better, and the construction is convenient, safe and reliable. The waterproof battery with cathode insulated electrode are suitable for all primary lithium batteries.

After practical tests, this scheme will not "leak" in a humid environment or the waterproof battery is immersed in water for a long time. The annual self-discharge rate of the battery is consistent with that in a dry environment, and the shell, leads and solder joints of the batteries are not corroded and can be used normally for a long time.

3. The production of waterproof battery

● Choose the right lithium battery housing

Choosing the right lithium battery case is the first step in waterproof measures. Usually, you can choose a shell with a waterproof function, or apply waterproof paint to the surface of the shell yourself.

● Use waterproof adhesive strips

Waterproof rubber strips can prevent moisture, dust and other substances from entering the inside of the lithium battery. Wrap the strip around the battery and make sure the gap at the bead is securely sealed.

● Use a waterproof protective case

If your lithium battery has no space to wrap the case, you can choose a waterproof protective case to protect the batteries. This protective sleeve prevents moisture and dust from entering the inside of the battery and protects the lithium battery from collision or vibration during use.

● Store lithium batteries properly

Proper storage of lithium batteries is also an effective waterproof measure. When storing lifepo4 battery, it should be placed in a dry, cool place to avoid direct sunlight or humid environments. If the lithium battery is not used for a long time, it is recommended to place it in a closed plastic bag to keep it dry.

● Avoid operating in water

This action may cause short circuits or battery leakage. If the waterproof battery must be operated in water, a waterproof device should be used. And make sure that the lithium battery shell, waterproof rubber strip, etc. are in good condition. Waterproof measures are very important when using lithium batteries.

Choosing the right lithium battery case, using waterproof strips and protective covers, properly storing batteries, and avoiding operation in water are all effective waterproof methods. By following these tips and recommendations, you can provide effective protection for lithium batteries and extend their lifespan.

4. How does lithium ion battery pack achieve dust and waterproof

After the lithium-ion battery is assembled, the whole insulating glue can be poured and then packaged, and it can be used underwater. Generally, lithium-ion battery packs should be tested for air tightness or waterproofing. To be completed with a high-precision air tightness detector, compressed air is used as the medium, and there is no need to do a submersion test.

According to the relevant experience of top 10 lithium battery companies in the world, whether the lithium-ion battery pack should be waterproof is done according to the corresponding product requirements of the batteries. Under normal circumstances, lithium-ion battery packs will not be waterproof, and lithium-ion battery packs to be waterproof design will cost more than ordinary battery packs.

In addition, when the product to be used has waterproof requirements, it must be waterproof. Dustproof and waterproof performance, the purpose is to prevent dust and water from affecting the insulation performance of cells, electrical components, control system circuit boards, etc. inside the battery pack, and corroding metal devices.

If the protective level of the lithium ion battery pack does not meet the requirements of dust and waterproofing, the environmental conditions of the battery cells and electrical components are in an uncontrollable state. In the general working environment, excessive dust will reduce the insulation performance of electrical devices.

If the humidity is too high, in addition to the impact on the insulation performance, it will also cause the self-discharge rate of the lithium-ion battery pack to rise, and the conductor is more susceptible to corrosion. In turn, the internal resistance of the system rises, and during the charging and discharging process, more electricity will be converted into ohmic heat and consumed.

The lithium-ion battery pack can completely prevent dust ingress, and can withstand water immersion for more than 30 minutes in a short time. At the same time, the battery cells and circuit boards of the battery have been improved and updated. And the power management function has been added, so that the number of cycles can reach more than 1000 times, ensuring the needs of users and life of the battery.

In terms of waterproof and dustproof, lead-acid batteries are far inferior to lithium-ion battery packs. The batteries of pure electric vehicles are generally placed at the chassis, so in the daily driving process, it is inevitable to encounter bumps and soaks. This obviously begins, to have a good waterproof and dustproof performance, so that lithium-ion batteries will be safer than lead-acid batteries.

5. Why a waterproof battery occurs

Hydropower is indispensable in our lives, and with the wide application of lithium batteries, it also needs to guard against water. Electrical equipment needs to be waterproof, as water can cause harm to it. The following explains why the design and use of lithium batteries need to be waterproof:

As a component of electrolyte, water has a certain influence on the formation of solid electrolyte interface film and battery performance of lithium ion batteries. The main manifestations are that the battery capacity becomes smaller, the discharge time becomes shorter, the internal resistance increases, the cycle capacity decays, and the battery expands.

Therefore, in the production process of lithium-ion batteries, the humidity of the environment and the water content of cathode and anode materials and electrolytes must be strictly controlled.

• The discharge capacity of the battery decreases with the increase of moisture in the waterproof battery.
• As the moisture of the battery increases, the internal resistance shows an upward trend.
• Battery capacity decay gradually decreases as moisture content increases.

Lithium iron phosphate batteries will expand, mainly because the presence of water after the formation of the SEI film causes LiPF6 to decompose to form HF gas. Therefore, when purchasing batteries, choosing the right waterproof battery is a must, it is best to cooperate with professional lithium battery custom companies, especially some of the instrument lithium batteries that can be used in the lithium battery industry, and it is particularly important to ensure its safety.

6. What to do if the battery gets into water

● Drain the stagnant water inside.

Dry the water and dry it with a hair dryer to reduce moisture residue, and finally let it dry naturally for 1-2 days. In addition, after the controller is installed, the controller can be wrapped in plastic, so as to enhance the waterproof effect of the controller.

● Do not rush to charge the waterproof battery after entering the water.

It is necessary to wait for it to dry sufficiently, otherwise it is easy to cause a short circuit of the cathode and anode of the waterproof battery. If the water is more serious, it is necessary to find a professional for maintenance, especially lithium batteries.

● Seek professional help

After entering the water, it is best to take the waterproof battery to the battery stores nearby first, it can continue to be used if it is not serious, and it is best to replace it directly if it is serious. Due to severe water ingress, charging will explode. The resistance of water is very large, which can easily cause the balance to get out of control.

7. Maintenance of waterproof battery

• The charging time should not be too long. Long-term charging is still very harmful to the waterproof battery.
• Do not charge in a high temperature environment. In winter, it is better to charge indoors.
• The number of charges should not be too frequent. It is best to charge when there is still a third of the charge, which is the most suitable.
• It is strictly forbidden to lose electricity when storing. Batteries that store electric vehicles in a power-loss state are prone to sulfation.
• Attaching lead sulfate crystals to the plates can block ion channels, resulting in insufficient charging and reduced waterproof battery capacity.

All batteries should also be charged once a month when they are not in use. Avoid hard braking, as frequent hard braking will drain waterproof  battery capacity. Pay attention to speed, the speed should not be too fast, the faster the speed, the greater the loss of waterproof battery.

8. Conclusion

Related articles: Top 5 battery electrolyte companies, lithium vs alkaline batteries, lithium ion battery pack