Read the charger. It'll have an input requirement and an output amount. If the charger is designed for 12v out and you are getting 100v then that's not good. If the charger is rated at 120v out and you get 100v, then that's not good either.
Your answer, however, is very simple: How many volts do the things you'd want to connect it to take? If it's higher than that, particularly if it's for the device it came with, you have your answer - hell no.
Read the charger. It'll have an input requirement and an output amount. If the charger is designed for 12v out and you are getting 100v then that's not good. If the charger is rated at 120v out and you get 100v, then that's not good either.
i would ask just how you are measuring this output,because there is no way a dc charger with an input of 120v will ever put out 100v dc.not ever.post the specs of the charger and how you are measuring the output.also,what are you charging with it?