48V 12AH lithium battery charger output voltage of about 18 volts, this is not normal. Nominal 48V charger, no load measurement, the output voltage should be about 51V. If the output voltage is only 18V, because the charger output voltage is lower than the voltage of the battery, then the charger is unable to charge the 48V battery. Therefore, in terms of output voltage, the charger has the possibility of chip damage. As for whether the pulse fluctuation is normal, this should be judged by referring to the performance of the charger. Now many chargers with repair function, one of the characteristics is pulse charging, the purpose is to reduce the high temperature generated by the battery when charging through intermittent charging, to protect the battery.