A study on quick charging method for small VRLA batteries

It is necessary for VRLA batteries to be charged quickly in many applications. Four-step tapering current charging is utilized to study quick charging for small VRLA batteries in this paper. With the measurement of charging parameters, such as charging time, water loss, temperature rise, as well as charging efficiency, it is found that the best initial current for quick charging is within 1–1.5 CA. Then a few group of batteries are taken to conduct cyclic life testing, also a recovery charging every 30 cycles is adopted since the charging regime is partial state of charging. The result shows that a better lasting life under quick charging regime is achieved compared to that under conventional charging. Thereafter failed batteries have been torndown and analyzed, it is found that favorable connectivity among positive particles and better activity of active material is formed under quick charging regime in comparison to that under conventional charging method through SEM, XRD and other electrochemical analysis. It is also found the failure mode under quick charging regime lies in the accumulation of passivation layer at the grid interface, which results in a higher impedance and eventually capacity deterioration.