Lead-acid Battery Electrode Cast Welding Process

Lead-acid battery has been used in industries more than 100 years since it was invented. Although Li-ion battery and Ni-MH battery become more and more popular, lead-acid battery can not be replaced by them because of its particular property. The capacity of lead-acid battery decreases after certain discharging cycles and fails finally. The failure mode includes positive grid corrosion, sulfation, runaway, negative strap corrosion and short circuit etc. Poor COS quality is a major processing factor which causes cracks between strap and lug. Many process parameters effect the quality of COS, mold temperature is the most important. In this paper the COS process is simulated through FEM to understand the phenomena of no fusion and lug melt because of mold temperature fluctuation. When the temperature of the lug close to the surface of strap equals to the solidification point of lug alloy, lug melt occurs in casting. VRLA battery uses lead calcium alloy for grid and lead tin alloy for strap, the COS process more likes soldering, COS of lead-tin strap is difficult and needs flux and tinning. The normal temperature of mold is 150℃. if the mold temperature is lower to 100℃, no fusion probably occurs, but lug melt happens if the mold temperature is higher up to 200℃. The old mold cooling system uses city water, the water pipe inner becomes dirty after service time, the mold temperature is difficult to adjust and fluctuates. In this paper we designs a refrigeration system to use DI water to cool the mold. The inlet temperature of mold is 15℃, outlet temperature is 80℃. At first cool the water to 50℃with a fin tube heat exchanger, Then cool the water to 15℃with a R22 refrigeration unit. This unit includes scroll compressor and bronzed plate evaporator. The performance of cooling system is good, It can keep the mold temperature at 150℃, decreases greatly the defects of no fusion and lug melt.