Electric vehicle battery old what the effects of monomer mix?

Electric vehicle battery is 2 v rated voltage, 12, 24, a set of voltage series, only 40 because each electric car drivers habits is different, maintenance methods are inconsistent, lead to the late drop in electric vehicle battery monomer, so when the gap when there is a certain distance, then will use time significantly shortened, lots of normal fork truck can't run, we need to replace the new electric car battery, as a result of the new battery internal resistance is small, the old battery internal resistance has a different degree of increase, when the mix of old and new battery charging, because the old battery internal resistance is big, partial pressure will be relatively large, extremely easy to cause overvoltage charging phenomenon, for the new battery, small internal resistance, small charging voltage but the current is big, and easy flow phenomenon, so should be avoided in the process of charging and discharging of old and new batteries to pretend to be. Because of single battery capacity is not only need to change, can change all at once only, not only the performance index is not enough to separate battery replacement, otherwise it will affect the whole battery for battery internal resistance of the imbalance of the play, shorten the service life of the battery for the whole. Charging, the internal resistance of the step-down big, on both ends of the battery voltage is not normal, long the bottom go to, which affect the normal cell. When to replace the new electric vehicle battery monomer, suggest a complete desulphurization, equalizing charge once, in order to make sure all the monomer battery consistency.