A 
lead acid battery for an 
electric vehicle has to face more use requirements of big capacity, long cycle life, big 
discharge current, short charging time and the like because the 
lead acid battery powers the vehicle, particularly a higher requirement on the charging technology. For the conventional three-stage charging technology, on the one hand, if the set breakover 
voltage from the first stage to the second stage is lower, the battery is insufficiently charged, which causes the quick reduction of the capacity of the battery, and if the set breakover 
voltage is higher, the loss of 
electrolyte and heating of the battery are caused due to positive 
overcharge; on the other hand, because different batteries are different in additive formulas, the ideal breakover 
voltage and breakover current are different; and the 
lead acid battery is passively charged by a charger, if the charger and the battery require different rated voltage or 
anode-
cathode directions, the damage of the battery or charger can be caused. Because a charging 
inference function module lowers the charging potential of the battery by continuously using negative pulse to 
discharge at the later stage of charging, the polarization 
potential difference between the charger and the battery is ensured, and the battery can be charged more fully; pole plate active materials of the battery are electrochemically reacted at a low potential, so that the gassing amount generated is greatly reduced; simultaneously, due to enough charging break time, the 
oxygen separated from the 
anode is ensured to undergo reaction with 
hydrogen to obtain water when reaching the 
cathode, and the enough time for heat dissipation is also ensured; and the service life of the lead acid battery is prolonged.