Battery chargers and batteries should pay attention to voltage matching. They can't be used across voltage. 72 volt batteries are composed of six batteries connected in series, while 60 volt batteries only have five batteries connected in series. The charging process of chargers is accomplished by controlling current or charging voltage. Each stage is different and the voltage varies, which may lead to a movie. If the switch is used, it can not be completed normally.

Battery voltage is not a fixed value, but floating in a certain range on the basis of nominal voltage. The upper limit of charging termination voltage is generally 1.2 times of nominal voltage, while the lower limit of discharge cut-off voltage is generally 0.9 of nominal voltage.
Single battery, 12*1.2=14.4 volt, 12*0.9=10.8 volt

For 72v batteries, the upper limit voltage for charging is 14.4*6=86.4 volts, while the lower limit discharge cut-off voltage is 10.8*6=64.8 volts.
For a 60 volt battery, the upper limit of charging voltage is =14.4*5=72 volts, and the lower limit discharge cut-off voltage is =10.8*5=54 volts.
Actually, the voltage may be a little different from the theoretical value, but it will not be too big. When chargers are charged, they will use different charging modes according to the different electric quantities.

At the beginning, the electricity is low, it is a constant current to charge, charging faster, equal current is less than a certain value, it is considered to be basically full, turn the lamp into a constant voltage mode, and finally constant voltage and then limit the current, charging under the so-called trickle current. So the process of different conversion is related to voltage.
If a 60V charger is used to charge a 72-volt battery, the battery will not be charged directly because of the high voltage, but because the highest output voltage is 72 volts, which is much lower than the charging upper limit voltage of 72-volt battery 86.4 volts, it is impossible to fill a 72-volt battery, so it is not ruled out that the current will always be very high for a long time. It may cause the battery to be short of water and damage the battery if the lamp cannot turn normally and the charging goes on all the time.

And full of dissatisfaction, for 72 volt motors, it must not run fast or far, it is easy to cause battery power shortage.
As for inversion, charging 60-volt batteries with 72-volt chargers is even more impractical, because the voltage is too high, and the batteries will be charged directly.

Unless it is a forced occasion, the charger voltage must match the battery voltage to use, otherwise it will directly damage the battery or shorten the battery life, serious may also cause fire because of heating problems.