Can you damage your laptop or phone when plugged into onboard at-seat power outlets?

I have a small program on my laptop that shows the incoming voltage, as well as the battery voltage. During a recent trip on LH, I plugged it into the at-seat power outlet. The incoming voltage varied quite a bit, sometimes up and down by as much as 23 volts. Was that bad for my laptop or its charger(only rated for 135v for North America)?