I owned a previous model of this trimmer and was very happy with it, although the previous model would only charge while on its stand.
THIS model does not have a stand and the cable plugs directly into it which is convenient.
One of my criteria for purchasing this model was whether or not it would continue working whilst connected to the charger because my last model no longer works when the battery died because it no longer holds charge (4 years later)
The answer received on amazon review is that it will work whilst connected to the device, but in truth it DOES NOT work whilst connected.
I'm disappointed in that, but it is a great product and if it lasts as long as my previous model than I'm ok with that.