Comparison of Gel battery and AGM battery - 4

○ Battery internal resistance and high current discharge capacity ○

The GLASS FIBER SEPARATOR used in the AGM sealed lead battery has a porosity of 90%, and sulfuric acid is adsorbed in it, and the battery adopts a tight assembly form, so the diffusion and electromigration of ions in the separator are very little hindered, so the AGM sealed lead battery has Low internal resistance, high current and fast discharge capability.

The electrolyte of the colloidal sealed lead battery is silicon gel. Although the diffusion speed of ions in the gel is close to the diffusion speed in the aqueous solution, the migration and diffusion of ions are affected by the structure of the gel. The more tortuous the pathway, the narrower the pores in the structure, and the more hindered it is. Therefore, the internal resistance of the Gel sealed lead-acid battery is larger than that of the AGM sealed lead-acid battery.

However, the test results show that the high-current discharge performance of the Gel sealed lead-acid battery is still very good, which fully meets the requirements of the relevant standards for the high-current discharge performance of the sealed battery. This may be because the concentration of acid and other related ions inside the porous electrode and in the liquid layer near the electrode plate plays a key role in high current discharge.

○ Thermal runaway ○     

Thermal runaway refers to the fact that the battery does not adjust the charging voltage in time at the later stage of charging (or the floating state), so that the charging current and temperature of the battery have a cumulative mutual enhancement effect. At this time, the temperature of the battery rises sharply, resulting in expansion and deformation of the battery tank, increase in the water loss rate, and even battery damage.

The above phenomenon is a very destructive phenomenon that occurs when AGM sealed lead-acid batteries are used improperly. This is because the AGM sealed lead-acid battery adopts a lean liquid tight assembly design, and 10% of the pores in the separator must be kept from entering the electrolyte, so the thermal conductivity inside the battery is poor and the heat capacity is small. When the oxygen generated by the positive electrode reaches the negative electrode and the negative electrode lead reacts, heat will be generated during charging. If it is not conducted away in time, the temperature of the battery will rise; if the charging voltage is not lowered in time, the charging current will increase, and the rate of oxygen evolution will increase. large, which in turn increases the battery temperature. Such a vicious cycle will lead to thermal runaway.

For open-type lead batteries, since there is no oxygen absorption by the cathode, and the amount of electrolyte is relatively large, the battery is easy to dissipate heat and has a large heat capacity. Of course, thermal runaway will not occur. The amount of electrolyte used in the gel sealed lead-acid battery is equivalent to that of the open-type lead-acid battery. The surrounding of the pole group and the gap between the battery and the tank is filled with gel electrolyte, which has a large heat capacity and heat dissipation, and will not cause heat accumulation.

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